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A&A
Volume 682, February 2024
Article Number A61
Number of page(s) 13
Section Interstellar and circumstellar matter
DOI https://doi.org/10.1051/0004-6361/202347486
Published online 05 February 2024

© The Authors 2024

Licence Creative CommonsOpen Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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1 Introduction

Star and planet formation takes place in highly dynamical environments in which the accretion history of these stars and planets can be far from being driven by the traditionally assumed symmetric collapse. Young stellar objects experience episodic anisotropic accretion as they travel through the interstellar medium and gravitationally interact with it (e.g., Lebreuilly et al. 2021; Kuffmeier et al. 2023). Modern radiointerferometers have recently revealed large-scale gaseous structures extending from young stars and their protoplanetary disks at various evolutionary stages. These structures are more commonly observed in near-infrared (NIR) scattered light (Ginski et al. 2021) or sub-millimeter molecular lines, such as CO (Yen et al. 2019), HCO+ (Akiyama et al. 2019), H2CO (Valdivia-Mena et al. 2022), and HC3N (Valdivia-Mena et al. 2023). Some of them are associated with infall of material as a stream from the surrounding environment (e.g., Tobin et al. 2010; Alves et al. 2020; Yen et al. 2014, 2019; Garufi et al. 2022; Pineda et al. 2023), via gravitational capture of a nearby cloud fragment during a close encounter (e.g., Scicluna et al. 2014; Dullemond et al. 2019; Ginski et al. 2021; Gupta et al. 2023, 2024), or as the result of material that is stripped through stellar flyby events (e.g., Cabrit et al. 2006; Dai et al. 2015; Kurtovic et al. 2018; Winter et al. 2018a; Ménard et al. 2020; Dong et al. 2022).

These so-called streamers have earned significant interest due to their potential impact on the inner star- and planet-forming system. Infalling material might induce perturbations in the disk, triggering instabilities (e.g., Bae et al. 2015; Hennebelle et al. 2017; Kuznetsova et al. 2022). These instabilities could then generate exponentially growing vortices, which act as traps for dust particles, where efficient planetesimal formation might begin (Barge & Sommeria 1995). Massive infall can also induce inner-to-outer disk misalignments (Kuffmeier et al. 2018,2021; Ginski et al. 2021), generate spiral waves (Thies et al. 2011; Hennebelle et al. 2017), induce accretion outbursts (e.g., Bonnell & Bastien 1992; Aspin & Reipurth 2003), and it can result in shocks with the disk material, leading to localized and significant alterations in the physical and chemical conditions of the disk (Garufi et al. 2022; Kuznetsova et al. 2022). These variations can in turn have a substantial impact on the structural and chemical evolution of the disk. Moreover, the infall of interstellar material can deliver significant amounts of mass to the central protostar and its protoplanetary disk, and this might help to reconcile the discrepancy between protoplanetary disk masses and exoplanet masses (Manara et al. 2018; Mulders et al. 2021). The simulations of Kuffmeier et al. (2023) provided an example of how protostars can sweep up material while moving through their natal clouds, and how they accrete substantial fractions of their final mass in regions that lie even tens of thousands au away from the positions at which we observe them today. In summary, infalling streamers are expected to dramatically influence the evolution of the involved star- and planet-forming systems. However, detecting and characterizing examples of these events is critical for constraining their frequency and magnitude, about which little is known so far.

Recently, Grant et al. (2021) reported the detection of extended continuum and molecular millimeter emission around [MGM12] 512 (RA = 05h40m13.789s, Dec = −07d32m 16.02s). Hereafter, we refer to the source as M512 for consistency with Grant et al. (2021). This young source is located in the Lynds 1641 region of the Orion A molecular cloud at a distance of ~420 pc, based on the Gaia DR3 parallax p ~ 2″.379 (Gaia Collaboration 2022). This distance is consistent with very long baseline interferometry estimates for Orion nebula cluster (e.g., 414 ±7 pc; Menten et al. 2007). In this work, we assume d = 420 pc. The source was classified as class I based on the 2–25 µm slope of the spectral energy distribution, α2–25 µm ~ 0.33 (Caratti o Garatti et al. 2012; Megeath et al. 2012). Finally, the main physical properties of M512 were reported by Caratti o Garatti et al. (2012) based on near-infrared spectroscopic measurements, and we summarize them in Table 1.

Here, we present new ALMA Band 3 (B3) observations M512 and combine them with archival ALMA Band 6 (B6) data to constrain the dust properties and mass of the extended structure. In Sect. 2, we describe the observations, in Sect. 3 we discuss the infalling nature of the extended arc around M512, and in Sect. 4, we measure the spectral index and derive a profile of the spectral index of the dust opacity. We discuss the results and the possible origins of this structure in Sect. 5 and summarize our conclusions in Sect. 6.

Table 1

Stellar parameters of M512 as reported by Caratti o Garatti et al. (2012), based on its spectral energy distribution and SofI near-infrared spectra.

2 Observations

M512 was observed with ALMA in B6 on 27 November 2019 (2019.1.01813.S, PI: van Terwisga, S.) and on 12 December 2019 (2019.1.00951.S, PI: Grant, S.). Both programs achieved a resolution of approximately 1″.14 and a reported maximum recoverable scale of roughly 11″.7. We refer to Grant et al. (2021) and van Terwisga et al. (2022) for further details and report the main characteristics of their observations in Table A.1.

We here present new ALMA B3 observations of M512 taken on 16 January 2023 (program 2022.1.00126.S, PI: Wendeborn, J.). These were designed to retrieve the 3 mm continuum flux of the extended emission around M512 that was first reported by Grant et al. (2021) at 1.3 mm, with a similar resolution. The bandpass and flux calibrator was J0423-0120, and the phase calibrator was J0542-0913 (see Table A.1).

The B3 data were initially calibrated by ALMA staff using the Cycle 9 ALMA interferometric pipeline (Hunter et al. 2023) within the Common Astronomical Software Applications (CASA; version 6.4.1–12). The B6 data were instead calibrated by the ALMA staff using CASA version 5.6.1-8 for both programs. We carried out further data reduction and calibration steps in both bands using CASA version 6.2.1.7. First, the ALMA cubes for each execution block were inspected and additional flagging was applied when necessary, for instance, to mask out all spectral lines. Among these lines, we note that the same arclike structure is clearly detected in DCO+ (216.11 GHz) and N2D+ (231.32 GHz). These lines are not spectrally resolved and thus could not be used in our kinematic analysis (Sect. 3).

We then channel-averaged the spectral windows of every execution block. First, we imaged the channel-averaged visibilities with the tclean CASA task and fit a Gaussian with imfit to identify the emission peak. Next, we used the fixvis function to shift the phase center to the position of the peak of M512 at the epoch of every observation. We are interested in measuring spectral indices, and we therefore checked for potential offsets among the visibility amplitudes of different execution blocks and found none above 3%.

We then phase-self-calibrated the data. We computed the phase corrections on the continuum spectral windows of each execution block using gaincal and applied them with applycal. This step aimed to correct phase errors between executions and between spectral windows. We repeated this procedure three times, progressively shortening the solution interval. In the first round, we set the solution interval of gaincal to inf, combined the scans within each execution block, and set gaintype = “G”, that is, the gains were determined for each polarization and spectral window. In the second and third rounds, we combined the spectral windows of each block, shortened the solution intervals to 60 and 10 s, respectively, and set gaintype = “T” to obtain one solution for both polarizations. At each round, we split and applied the table computed at the previous steps to each execution block. The self-calibration yielded peak S/N improvements of about 15% as the phase of the visibilities were already well constrained. We did not find any appreciable improvement in the properties of the noise and signal-to-noise ratio for phase-only self-calibration steps with even smaller time intervals. The final peak signal-to-noise ratio of the B3 image is 355, and it is 218 for the B6 image.

Finally, we imaged the visibilities to carry out the rest of the analysis. Because the emission is extended, we ran the tclean routine setting pbcor = True in order to correct for the primary beam attenuation. We deconvolved the images using the hogbom algorithm (Högbom 1974) with the Briggs weighting scheme, and we tried a number of robust parameter choices to find the optimal balance between resolution and sensitivity. We finally carried out the analysis on images with robust = 1, a pixel size of 0″.2 (84 au at the distance of M512, one-seventh of the synthesized beam) and an image size of 300 pixels. When running tclean, we manually masked the emission, which is comprised of both the bright inner disk and the extended streamer, and CLEANed down to 1.5 times the image rms. Because we wish to compare emission that traces the same physical scales, we used a uvtaper to weight the visibilities in order to obtain similar synthesized beams for the two bands (1″.5 × 1″.2, PA = 72°). Finally, we smoothed the images to the same resolution of 1″.6, which is roughly equal to the width of the extended emission at the 3σ level recovered by Grant et al. (2021) with robust = 0.5 (see their Fig. 13). We recovered an arc-like structure that extends radially to about 4000 au (Fig. 1). We note that the length of the streamer as observed in this study is to be considered a lower limit because the interferometric observations might have filtered out larger-scale emission. Moreover, we report a C18 O J = 2−1 transition moment-one map of M512 obtained with the observations of ALMA program 2019.1.00951.S (Fig. 2). In what follows, we focus on characterizing the kinematics and the dust content of this extended structure, to which we refer as “streamer” hereafter.

thumbnail Fig. 1

ALMA Band 3 (100 GHz) continuum emission of M512 with [3, 7, 100]σ contours overplotted in white (left). ALMA Band 6 (230 GHz) with [3, 10, 100]σ contours overplotted in white (center). The spectral index as measured from Eq. (1) using only pixels with flux above the 3σ noise level (right). The x- and y-axes report the offset from the central source in arcseconds. The color bars represent the flux density (mJy beam−1) for the ALMA observations (left, center) and the value of the spectral index (right). The images have been created applying a uv taper to the visibilities, with Briggs weighting and robust = 1. Then we have smoothed them to the same resolution of 1″.6, which is roughly the width of the extended emission. The beam is reported in the lower left corner.

3 Streamer kinematics

Whether extended structures such as the one linked to M512 are actually infalling on the central protoplanetary disks is a problem that requires precise constraints on the geometry and physical properties of the system. In our case, the unknown details of the geometry of the inner disk, due to somewhat limited spatial resolution, introduce uncertainties in the interpretation of the velocity structure around the source. To complicate the problem further, both the mass and system velocity are uncertain. The former is affected by the precision to which spectral types are determined by near-infrared spectra (Caratti o Garatti et al. 2012), the high extinction of this region (e.g., Gutermuth et al. 2011), and the contribution of the inner embedding material connected to an envelope remnant or to the streamer itself. Furthermore, the limited spectral resolution and the potentially high optical depth of the CO isotopologs limits the accuracy with which we can estimate the system velocity. In this section, we analyze the C18 O J = 2−1 transition that was presented in Grant et al. (2021). Among the other isotopologs, we chose this transition because its emission is optically thinner than that of 12CO and 13CO and it is less affected by foreground absorption. We imaged the spectral cube containing the spectral window of the line with the same scheme of the continuum dataset. During the cleaning, we masked the emission manually, channel-by-channel, in order to capture its complex morphology.

The moment-one map shows an arc-like feature consistent with the 1.3 mm dust continuum emission region, and it is characterized by a progression from lower to higher velocities when approaching the protostar from afar (Fig. 2). This gradient may be indicative of infalling motions toward the inner object (as observed in, e.g., Per-emb 2; Pineda et al. 2020, Per-emb 50 Valdivia-Mena et al. 2022). The velocity transition between the streamer and the inner material might also indicate rotation of the innermost embedding material. We attempted to model the C18O kinematics to constrain whether the data are consistent with infalling motion. We analyzed the spectral cube with the code called trajectory of infalling particles in streamers around young stars (TIPSY; Gupta et al. 2023, 2024). The input for the code were the mass of the central object and its line-of-sight velocity (vsys). We set the former to 0.15 M⊙, as reported in Table 1. We note that the inner envelope mass and even the streamer mass might contribute significantly to influencing the ballistic motion of a particle. For the latter, we explored a range of systemic velocities consistent with the observed C18O spectral line, between 2.9 and 3.9 km s−1. Based on these constraints, TIPSY solved analytical kinematics equations for an infalling parcel of gas that feels the gravity of a central source from Mendoza et al. (2009) and computed its trajectory throughout the region over which we detect emission, as well as the kinetic gravitational (and thus total Etot) energy of the parcel and its infall timescale. We overplot a TIPSY fit model to the moment-one map in Fig. 2 to show that the arc-like feature around M512 is consistent with the infall of material. The available data are consistent with infall for velocities in the explored range of vsys, but the material is only loosely bound (Etot ≲ 0) for vsys ≳ 3.7 km s−1. The TIPSY model constrains the infall timescales to about 50 kyr. We overplot the radial velocities as fit by TIPSY in a position-velocity diagram (PVD; Fig. 2) obtained using pvextractor (Ginsburg et al. 2016). The PVD was extracted along the infalling trajectory shown in Fig. 2, and it includes the inner region. The width of the selected path is equivalent to the beam, 1″.6. The TIPSY model is consistent with the radial velocities of the observed emission. New observations will be key to constraining the geometry, the system velocity, and the effect of the streamer mass on the infall trajectories.

In Sect. 5, we discuss further qualitative arguments that support the infall scenario against alternatives such as stripping due to a flyby or the cavity wall of an outflow. We thus tentatively suggest that the arc-like structure detected around M512 is an infalling streamer.

thumbnail Fig. 2

Moment-one map of the 18CO J = 2−1 transition (>2σ) around M512 (left). The black contours are the B6 continuum [3, 10, 100]σ levels. The green line is the TIPSY model trajectory for M = 0.15 M⊙ and vsys = 3.25 km s−1. The position-velocity diagram of the streamer emission (grey contours) is extracted along the TIPSY trajectory and includes the inner protostellar region (right). The TIPSY fit to the radial velocities is reported as a green line.

4 Spectral index

The slope of the radio spectrum α=log10F(v2)−log10F(v1)log10v2−log10v1,$\alpha = {{{{\log }_{10}}F\left( {{v_2}} \right) - {{\log }_{10}}F\left( {{v_1}} \right)} \over {{{\log }_{10}}{v_2} - {{\log }_{10}}{v_1}}},$(1)

where vi are the observed frequencies, can provide valuable insights into the properties of interstellar dust grains. Because the dust opacity follows a power-law relation κ ∝ vβ at the millimeter end of the spectrum, β = α − 2 in the optically thin regime and if the Rayleigh–Jeans (RJ) approximation holds (e.g., Draine 2006; Beckwith & Sargent 1991; Miyake & Nakagawa 1993; Natta et al. 2007). The typical dust opacity index observed for the interstellar medium, β ~ 1.6, is usually interpreted to mean that the maximum grain sizes of the dust population range from 100 Å to 0.3 µm (Weingartner & Draine 2001). In contrast, a value β < 1, which is often measured in class II objects, indicates the presence of larger grains, with sizes a ≥ 1 mm, in more evolved disks (Beckwith & Sargent 1991; Ricci et al. 2010; Testi et al. 2014; Macías et al. 2021).

In the following analysis, we present maps of the spectral index α and the profile of the dust opacity spectral index β in the emission region of M512 and its streamer.

4.1 Spectral index maps

Using the ALMA B3 and B6 maps, we calculated the spectral index α at each pixel in our smoothed maps. This procedure yielded the spectral index map shown in Fig. 1. Within the inner ~600 au region, centered on the protoplanetary disk of this young source, the spectral index is approximately α ~ 2, which indicates optically thick emission (Beckwith & Sargent 1991). The high optical depth of this compact region suggests an optically thick disk that is diluted in a more extended sky area by the finite resolution of the observations. To ensure that the spectral index of the inner end of the streamer was not contaminated by this central emission, we modeled and subtracted the contribution of the latter. We fit a 2D Gaussian to the inner region in the image plane. The fitting results are provided in Table B.1, and the model and residuals are displayed in Appendix B. The compact emission extends for 1″.4 (2σ, 574 au) and might comprise a combination of the inner end of the streamer, remnants of the original envelope of M512, and a more compact protoplanetary disk. Higher-resolution observations will be key to discern the extent of the inner disk. We then subtracted the Gaussian model from the image to isolate the contribution of the streamer (Fig. 3). Finally, we computed the spectral index of the streamer emission, αS (see Figs. 1 and 3). We observe a spectral index of approximately αS ~ 3.2 along the entire streamer, which indicates optically thin emission. Because of the dust temperature profile we considered to derive the spectral index of the dust opacity (see Eq. (1)), we derive τ = − ln(1 − Iv/Bv(T)) < 0.05 in B6 along the full arc. As a sanity check, we ran a similar analysis in the uv plane, where we subtracted a point source from the visibilities and then computed the spectral index as a function of uv distance. We obtained consistent results (see Appendix B).

thumbnail Fig. 3

Same as Fig. 1, but after subtraction of the inner optically thick region. Only the pixels with flux above 3σ are shown for each inset.

4.2 Dust opacity spectral index

To investigate whether and how the optical properties of the dust change along the streamer M512, we divided the streamer into spatial bins and derived the spectral index of the dust opacity β within each bin. In order to select the bins, we used a logarithmic spiral with manually tuned parameters to adapt it to the shape of the streamer. We then selected points along the spiral as centers for circular apertures as large as the streamer width (see Fig. 4). The aperture radius is twice the beam aperture, and each aperture contained roughly 160 pixels. When we assume that the main heating mechanism for the dust is the irradiation from the central source, we can use the radial temperature profile that Motte & André (2001) derived for spherical dusty envelopes as a first approximation, T(r)=38 K(LL⊙)0.2(r100au)−0.4.$T(r) = 38{\rm{K}}{\left( {{L \over {{L_ \odot }}}} \right)^{0.2}}{\left( {{r \over {100{\rm{au}}}}} \right)^{ - 0.4}}.$(2)

This equation yields temperatures in the range of 21–8 K across the scales of the streamer, that is, 600 to 4000 au. We note that these distances from the central source assume that the streamer lies in the plane of the sky. At λ = 1.3 mm, the temperature T = 8 K implies that the RJ approximation is not valid (hv/kB T ~ 1). We thus introduced a correction to the simple α = β − 2 case for the low temperatures that would otherwise artificially lower the derived β, which we then derive as β=log[ (Fv2(r)/Fv1(r))/(Bv1(Td(r))/Bv2(Td(r))) ]log(v2/v1),$\beta = {{\log \left[ {\left( {{F_{{v_2}}}(r)/{F_{{v_1}}}(r)} \right)/\left( {{B_{{v_1}}}\left( {{T_{\rm{d}}}(r)} \right)/{B_{{v_2}}}\left( {{T_{\rm{d}}}(r)} \right)} \right)} \right]} \over {\log \left( {{v_2}/{v_1}} \right)}},$(3)

where the ALMA B6 and B3 representative frequencies are v2 = 230 GHz, v1 = 100 GHz, Td is the temperature of the dust, and Bvi(Td)${B_{{v_i}}}\left( {{T_{\rm{d}}}} \right)$ is the Planck function value at the two frequencies.

Finally, we computed the statistical error on the spectral index as δα2(=δβ2)=(1lnv2−lnv1)2(σ12Fv12+σ22Fv22),$\delta {\alpha ^2}\left( { = \delta {\beta ^2}} \right) = {\left( {{1 \over {\ln {v_2} - \ln {v_1}}}} \right)^2}\left( {{{\sigma _1^2} \over {F_{{v_1}}^2}} + {{\sigma _2^2} \over {F_{{v_2}}^2}}} \right),$(4)

where σi, Fvi2${\sigma _i},\,F_{{v_i}}^2$ are the primary-beam-corrected rms and fluxes in each distance bin for the two bands. We considered the same error for β because we assumed an exact value for the temperature in Eq. (3). In addition to the statistical error, the systematic calibration uncertainty on the B3 and B6 fluxes for ALMA of 1σ = 5% (Remijan et al. 2019) should be considered. Within the same bins, we also computed α using Eq. (1), and we show the resulting β = α − 2 proxy and the β(T) profile in Fig. 4.

We find a mean β = 1.62 ± 0.04 throughout the whole structure. Finally, we tested the two extreme scenarios in which the temperature is fixed at 21 or 8 K for the whole structure. The arc might self-shield against the internal radiation and might therefore be colder on average, or conversely, significant external irradiation from Orion OB stars might lead to higher temperatures in the outer arc (Haworth 2021)1. In any case, the β measured with both fixed temperatures only changes by <10% with respect to the β obtained using the temperature profile.

thumbnail Fig. 4

Profile of the spectral index β of the dust opacity along the length of the streamer. The approximation β = α − 2 is shown as the orange line, and β, corrected for the deviation from the RJ approximation, is shown as the violet line. This profile has been obtained starting from the maps in Fig. 3, where the central emission had been modeled and subtracted. The centers of the selected apertures in which we derive β are highlighted in white among all the points that sample the manually defined logarithmic spiral in the B6 map as an example (upper inset). Throughout the whole structure, β ~ 1.6. The gray band represents ISM-like β.

5 Discussion

We discuss the interpretation of the derived dust-opacity index, estimate the mass of the surrounding material, and weigh the implications of such an event on a planet-forming system, as well as its possible origins.

5.1 Dust properties of the streamer

The retrieved continuum flux of the streamer around M512 implies a relatively high dust mass that can either be distributed in large numbers of small grains or in smaller numbers of large grains. It is thus important to constrain the maximum grain size of the distribution in order to constrain its mass content.

In the case of a distribution of spherical compact grains, the Mie scattering theory predicts that the derived β ~ 1.6 (Fig. 4) is consistent with a dust population for which the maximum grain size is submicron (Draine 2006). If the grains were instead porous, β ~ 1.6 could be consistent with a dust distribution where the maximum grain size lies in a smoother range from submicron to one millimeter (e.g. Birnstiel et al. 2018).

It has recently been suggested that dust can grow up to millimeter sizes even in protostellar envelopes. β values lower than ~1.6 have been measured in the inner envelopes of a sample of class 0/I objects (e.g., Kwon et al. 2009; Miotello et al. 2014; Galametz et al. 2019; Cacciapuoti et al. 2023). However, models show that dust cannot grow more than a few µm in more diffuse molecular clouds cores (e.g., Ormel et al. 2009; Lebreuilly et al. 2023), where the submillimeter-dust opacity spectral index β ~ 1.6 (Draine 2006). Scattered-light observations of these environments have also independently been interpreted as the presence of grains up to only ~10 µm (e.g., Steinacker et al. 2010, 2014, 2015). Thus, the β = 1 6 measured for the streamer of M512 is consistent with the properties of ISM-like dust grains.

5.2 Mass constraints and infall rate

The delivery rate of mass onto M512 is critical to assess the implications that the event might have for the subsequent evolution of the system. In the optically thin regime, the dust mass of the observed streamer can be derived as (Hildebrand 1983): M=d2 FvκvBv(Td),$M = {{{d^2}{{\rm{F}}_v}} \over {{\kappa _v}{B_v}\left( {{T_{\rm{d}}}} \right)}},$(5)

where d is the distance to the source, Fv is the flux density of the structure, κv is the dust opacity, and Bv (Td) is the value of the Planck function at a frequency v. We considered a distance of 420 pc (see Sect. 1), and the temperature was given by Eq. (2). In order to measure the mass of the streamer and take the expected temperature variation along the arc into account, we considered the logarithmic spiral we mentioned in Sect. 5.1 that is shown in Fig. 4. For each selected aperture on the spiral, we assigned each pixel above the 3σ threshold to the closest aperture center, measured the total flux in the bin so defined, and computed the temperature with Eq. (2), where r is the projected radial distance of each aperture center from the source.

When we assume DSHARP dust properties (Birnstiel et al. 2018), the absorption opacity of a dust grain distribution that is characterized by ISM-like spectral indices such as we measure for the streamer of M512, and a typical power-law n(a) ∝ a−3.5, is κ1.3mm = 0.4 g cm−2. The solid mass of the streamer thus amounts to Mduststreamer=245±25 M⊕$M_{{\rm{dust}}}^{{\rm{streamer}}} = 245 \pm 25\,{M_ \oplus }$. On the other hand, considering the usual assumptions for protoplanetary disks to derive the mass of the inner region (e.g., Andrews et al. 2013; Pascucci et al. 2016; Ansdell et al. 2016), that is, a temperature of 20 K and an absorption opacity κ1.3mm = 2.25 g cm−2, we obtain Mdustinner=58±6 M⊕$M_{{\rm{dust}}}^{{\rm{inner}}} = 58 \pm 6\,{M_ \oplus }$, given the integrated flux in Table B.1. The reported uncertainties on the derived masses only reflect the dominant flux calibration error of 10%. We note that because the compact inner emission is optically thick, the mass estimates for the inner region can be off by a factor up to ~5 (Ballering & Eisner 2019; Ribas et al. 2020; Macías et al. 2021; Xin et al. 2023; Rilinger et al. 2023), and a further underestimate of the millimeter-derived mass can be due to scattering effects in the very inner optically thick region (Zhu et al. 2019; Liu 2019). Taking all of this into account, we find that the mass of the streamer seems to exceed or be comparable to the mass of the inner region. Based on the resolution of the observations, this mass does not correspond to the mass of the protoplanetary disk alone, but also accounts for contribution from the inner infalling material.

Finally, we can constrain the infall rate onto M512 and its disk. Considering the typical free-fall timescale, tff∝r3/GM${t_{{\rm{ff}}}} \propto \sqrt {{r^3}/GM} $, a particle with null initial velocity would fall from 4000 au onto the 0.15 M⊙ protostar in roughly 50 kyr. This estimate is consistent with the TIPSY outputs ran in Sect. 3. Thus, when we assume that the whole streamer will infall onto the inner system and when we assume a typical dust-to-gas ratio of 0.01, the total mass infall rate is M˙=1.510−6M⊙yr−1$\dot M = {1.510^{ - 6}}{M_ \odot }{\rm{y}}{{\rm{r}}^{ - 1}}$.

However, it is imperative to bear in mind that the infall rate may be lower if the streamer does not interact in its entirety with the inner protoplanetary disk. Consequently, while we discuss the implications of our study under the assumption that the entire streamer ultimately infalls on the inner disk, we emphasize the sensitivity of these outcomes on the mass that is actually captured by the source. Observations with higher spatial and spectral resolution are needed to remove the remaining sources of uncertainty of the analysis: The geometry of the inner system, the line-of-sight velocity of the star, and the impact of the infall via shock tracers such as SO (e.g., Garufi et al. 2022). It is noteworthy that outbursts observed for young stellar objects have been proposed to be triggered by massive accretion events (e.g., Bonnell & Bastien 1992; Aspin & Reipurth 2003). M512 might represent a rare case for which we witness a late-infall event that delivers mass at a significantly high rate. When we assume infall of the entire structure and outburst durations of ~100 yr, these rates would imply a possible future accretion event of 7.5 × 10−4 M⊙ yr−1, or a series of smaller events. For example, if accretion were to build up material in the disk for 10 kyr2, this would imply FUOr-like accretion (~10−4 M⊙ yr−1, Kenyon et al. 1988), which might then cause outbursts. The accretion rate of M512 has been characterized as being in a quite ordinary accretion state, that is, Lacc < L*, with M˙~2×10−7M⊙yr−1$\dot M\~2 \times {10^{ - 7}}{M_ \odot }{\rm{y}}{{\rm{r}}^{ - 1}}$, based on single-epoch observations (Caratti o Garatti et al. 2012). However, M512 has been classified as a bursting source based on multi-epoch WISE 3.4 µm and 4.6 µm photometry by Park et al. (2021). Over the course of 6.5 yr and with a time resolution of 0.5 yr, Park et al. (2021) observed three sharp increases in the flux by a factor ~2.5 in both bands. This source represents an exciting case for exploring the possible link between infalling streamers and accretion outbursts.

Furthermore, the mass-infall rate onto M512 is similar to the rate used, for instance, by Bae et al. (2015) and Kuznetsova et al. (2022) in their simulations, in which they found that material infalling at these high rates on protoplanetary disks has the power to drive significant substructures. M512 thus represents a unique source for probing whether infall can drive substructures, which are often regarded as birthplaces of planets.

We note that an additional source of uncertainty for the derived masses comes from the chosen dust opacities. While we considered DSHARP opacities so far, other works made use of different prescriptions, such as the DIANA opacities (Min et al. 2016) or opacities constrained from Solar System observations (Pollack et al. 1994). These alternative choices would imply absorption opacities that are systematically higher in the submillimeter regime, up to about three or ten times those of the DSHARP, respectively. The mass derived through them would therefore be up to ten times lower both for the streamer and the inner disk. We point out that consistent choices of opacities imply the same ratio of the streamer and the disk mass.

5.3 Origins and frequency

The origin of streamers is still a matter of debate. Some authors have proposed that streamers are a channeled inflow of material from protostellar envelopes or even from beyond the scales of prestellar cores (e.g., Yen et al. 2014, 2019; Pineda et al. 2020). The streamer in the surroundings of M512 discussed here, however, is not reminiscent of irregular envelopes, and it is infalling in an apparently ordered, arc-like manner (see Sect. 3). Moreover, CO observations seem to indicate that M512 lost most of its initial envelope (Grant et al. 2021). Other explanations involve the interaction of M512 with close-by objects, such as a flyby with another stellar object or interactions with close interstellar clouds.

Flyby events might be quite common in star-forming regions, especially during the protostellar stages, where stars form close to each other in clusters (Pfalzner 2013; Winter et al. 2018b; Lebreuilly et al. 2021; Offner et al. 2023). In this sense, the morphology of M512 is reminiscent of the stages observed for RW Aurigae (Cabrit et al. 2006; Dai et al. 2015; Rodriguez et al. 2018), AS 205 (Kurtovic et al. 2018), UX Tau (Ménard et al. 2020), and Z CMa (Dong et al. 2022), binary-star systems for which a long molecular arm extends from the primary star and points toward a secondary object. In Appendix C we discuss that a close encounter might have occurred between M512 and another source a few hundred thousand years ago. This is much longer than most flyby events for which we still observe stripped material. Simulations indeed suggest that the re-circularization of material happens in a few thousand years (e.g., Cuello et al. 2023), making the observation of such an event extremely unlikely. Moreover, spirals excited due to stellar flybys are usually of the same order of magnitude of the outer radius of the stripped disk (≲3 Rout; Smallwood et al. 2023), while the arc we observe extends for thousands of astronomical units. The flyby scenario is thus hard to reconcile with our observations. We expand on our arguments in Appendix C.

The velocity gradient we observe in the arc of M512 (see Fig. 2) is also consistent with the capture of material from a nearby cloud with a nonzero initial velocity. The material is then accelerated toward the central star. Scicluna et al. (2014) and Dullemond et al. (2019) explored the possibility that forming protostars might capture material from nearby small clouds as they travel within their natal environment. Because of its non-null initial angular momentum, the material in this scenario does not fall directly onto the protostar, but feeds the disk, or even forms a new one. This capture process has been proposed to explain the observed infrared excess around very evolved ≥10 Myr old stars (e.g., Beccari et al. 2010; De Marchi et al. 2013a,b) and the M*−M˙${M_*} - \dot M$ correlation in pre-main-sequence stars (e.g., Padoan et al. 2005, 2014; Throop & Bally 2008). Examples of objects that might be undergoing scenarios like this are AB Aur (Nakajima & Golimowski 1995; Grady et al. 1999) and HD 100546 (Ardila et al. 2007). The hydrodynamics simulations of Dullemond et al. (2019) and Kuffmeier et al. (2020) demonstrated that the capture of cloud fragments would lead to the formation of arc-shaped structures much like the one observed in M512 (Scicluna et al. 2014; Dullemond et al. 2019). Additionally, Scicluna et al. (2014) computed the probability of cloudlet capture by a stellar object in different density conditions of the environment. Scicluna et al. (2014) found that for a region in which dense clumps occupy a fraction fV of the total volume, the number of stars that is expected to be observed as cloudlet-capture accretors at a given time is larger by an order of magnitude than the volume filling-factor of dense clumps. Thus, if dense clumps only occupy a volume fraction as small as fV = 10−4, we expect one in a thousand objects to show late accretion. We note that M512 is one of three objects showing extended continuum emission in the Survey of Orion Disks with ALMA (SODA; van Terwisga et al. 2022), which includes 873 objects. The overall median accreted mass in all the simulation grids explored in this survey is 0.01M⊙. Scicluna et al. (2014) also demonstrated that the structures formed due to capture can last for even 104–105 yr (see their Sect. 2). These values are comparable to the streamer mass of M512 and to its free-fall timescale. Furthermore, we note that dust grains in ISM clouds should not exceed a few tenths of microns (e.g., Mathis et al. 1977), which further supports a scenario in which the β ~ 1.6 measured in Sect. 5.1 indicates ISM-like grains. Larger-scale maps than available at present would be helpful to link the streaming material around M512 with the neighboring environment, and to understand whether the observed streamer presented in this work is replenished by the surrounding environment or if it represents the full extent of the mass that will be delivered to the disk of M512.

Last, continuum emission has sometimes been detected along the cavity walls of protostellar outflows, where the dust might be brighter because the temperatures are higher (e.g., Maury et al. 2018; Le Gouellec et al. 2023). In the case of M512, however, the arc-like emission is quite bent and not reminiscent of more cone-like outflow cavities (e.g., Garufi et al. 2021; Hsieh et al. 2023). Additionally, CO emission is optically thick, and the C18O line profile indicates low velocities, about 500–700 ms−1, and we observe both redshifted and blueshifted emission within the same arc (Fig. 2). Finally, M512 is a class I very low mass star, implying that such a large outflow would be unlikely. It is thus not straightforward to reconcile our observations with the outflow scenario. We also note that our mass estimates would still be valid with the caveat that at the cavity wall of a low-velocity outflow, temperatures would be slightly higher than what we assumed for the cold-streamer case (e.g., Flores-Rivera et al. 2021). This would imply a mass that is a factor of a few lower, and thus still a significantly high dust mass (Mdust ≳ 50 M⊕). When we consider typical class I outflow mass-loss rates of a few 10−8 M⊙ yr−1 (Fiorellino et al. 2021), it would take over 1 Myr yr to lift Mdust ≳ 50 M⊕, while the mass-loss rates quickly decline over the first ~105 yr of star formation. We thus tentatively discard this scenario. However, nonisotropic accretion from the envelope to the central source has been suggested to occur along the cavity walls of outflows (Le Gouellec et al. 2019; Cabedo et al. 2021). Observations of bright and optically thin outflow tracers will help to clarify this case, together with higher-resolution observations of the central source to resolve the geometry of the disk and thus the direction along which an outflow could be launched.

In summary, given the constraints of Sect. 3 and the qualitative arguments laid out in this section, we repeat our suggestion that the arc-like structure around M512 is an infalling streamer, possibly caused by a cloudlet-capture event.

5.4 Implications for planet formation

Streamers can have significant implications for planet formation and for the evolution of a protoplanetary disk. M512 represents a unique case for which dust continuum emission is detected in two ALMA bands, thus enabling us to better constrain its dust properties and mass content. The structure we observe delivers a substantial amount of mass to the inner disk of M512, carrying several significant implications that we discuss below. In what follows, we assume that the whole streamer will infall onto the central disk, consistently with the bound solutions found in the kinematical analysis we laid out in Sect. 3. However, it is possible that only a fraction of the detected structure will infall onto the inner system, and the infall rate might therefore be lower by a factor of a few.

To begin with, the streamer replenishes the system with an amount of mass that exceeds or is comparable to the mass of the protoplanetary disk. If the infalling dust were captured by a nearby cloudlet in which the maximum grain sizes are 1–10 µm (see Sect. 5.1), a total mass of up to 0.075 M⊙ might infall on the disk of M512. The infall can potentially double the mass available for planet formation in the system. The mass budget problem, that is, the apparent lack of mass that is required to form known exoplanetary systems starting from the class II protoplanetary disks we observe in the Galaxy (e.g., Testi et al. 2016; Manara et al. 2018; Williams et al. 2019; Sanchis et al. 2020; Tychoniec et al. 2020), could thus be partially bridged by late infall of material onto evolved disks. Additionally, the supply of material around low-mass stars such as M512 could represent a possibility for the formation of gas giants around this type of object. While exoplanets like this are detected, if rarely (e.g., Morales et al. 2019; Bryant et al. 2023), their formation pathways remain unclear (Liu et al. 2020).

Additionally, M512 is a candidate on which to study the origin of substructures in evolved disks. Infall of material onto disks has been proposed to be one of the mechanisms that can trigger such substructures (Thies et al. 2011; Hennebelle et al. 2017; Kuffmeier et al. 2018; Ginski et al. 2021). Bae et al. (2015) and Kuznetsova et al. (2022) demonstrated that infall can drive the formation of rings and gaps in disks with infall rates that are consistent with what we find for M512. A possible instance of this process was detected by Segura-Cox et al. (2020), who observed rings and gaps in in the protoplanetary disk around Oph IRS63, which was recently shown to be subject to anisotropic infall (Flores et al. 2023). Another example is HL Tau, where both disk structures and an infalling streamer were observed (ALMA Partnership et al. 2015; Yen et al. 2019). The study of the impact of streamers on disks that display substructures can inform us about the necessity, or lack thereof, of invoking planets that carve out these structures at the early stages of star and planet formation. Moreover, the formation of substructures and the induction of turbulence in the disk can alter the timescales of grain growth because the clumping of grains is more efficient under these conditions. Higher-resolution observations of M512 will be key to unveiling the geometry of its inner disk and to searching for potential substructures.

Last, the infalling material will impact the disk at some radius and will potentially shock its surroundings. In the vicinity of the shock, the disk temperature will rise (Garufi et al. 2022). Thus, the streamer will change the physical and chemical properties of the disk, as shown for example for HL Tau in (Garufi et al. 2022). M512 is known to undergo outbursts (Park et al. 2021) that can greatly alter the physical and chemical properties of protoplanetary disks by influencing both the evolution of dust (Houge & Krijt 2023) and gas (Owen & Jacquet 2014; Wiebe et al. 2019). To determine whether these properties are linked to the infalling streamer is an exciting matter for further studies.

6 Conclusions

We have presented new ALMA B3 observations of M512 in the Lynds 1641 region of the Orion A molecular cloud and combined them with archival ALMA B6 data to constrain the dust properties of a 4000 au arc-like structure extending from the central source. Our conclusions are listed below:

  • The structure is characterized by a velocity gradient consistent with infall (see Fig. 2). The morphology of the extended emission and the velocity gradient are consistent with the capture and infall of material from a nearby cloudlet;

  • The compact (~600 au) region surrounding M512 is optically thick at the wavelengths considered here (α ~ 2). Higher-resolution observations will be key for studying this inner region and for constraining its geometry and the impact of the infall event, which we cannot probe with current observations;

  • The streamer is optically thin with αS ~ 3.2 throughout the whole structure. Accounting for the low temperatures expected at its scales, we obtain a spectral index of the dust opacity β = 1.62 ± 0.04, which is typical of ISM-like dust (Sect. 5.1);

  • We constrain the dust mass of the streamer to be ~250 M⊕3 (see Sect. 5.2). Based on typical free-fall timescales, the streamer might deliver up to 1.5 × 10−6 M⊙ yr−1 onto the inner disk, and it might last about 50 kyr. We note that these estimates assume that the whole structure will infall;

  • We discuss the possible origins and impact that this event can have on the planet-forming disk of M512, including the replenishment of mass, the formation of substructures, and changes in the physical and chemical conditions due to shocks and/or accretion outbursts (Sect. 5.4).

Streamer observations are a new window for insight into star and planet formation. They remind us that this process is not isolated and is highly dynamic within star-forming regions. Further observations are necessary to link streamers to their potential large-scale progenitors and to test the impact that streamers have on planet-forming disks on smaller scales. M512 is a unique source that will play a crucial role in these studies. This target is a rare opportunity for studying both gas and dust in their physical properties and dynamics, which would enable a comprehensive comparison to dedicated models.

Acknowledgements

This work was partly supported by the Italian Ministero dell’Istruzione, Università e Ricerca through the grant Progetti Premiali 2012-iALMA (CUP C52I13000140001), by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) – Ref no. 325594231 FOR 2634/2 TE 1024/2-1, by the DFG Cluster of Excellence Origins (www.origins-cluster.de). This project has received funding from the European Union’s Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement No 823823 (DUSTBUSTERS) and from the European Research Council (ERC) via the ERC Synergy Grant ECOGAL (grant 855130). Funded by the European Union (ERC, WANDA, 101039452). Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the European Research Council Executive Agency. Neither the European Union nor the granting authority can be held responsible for them. This work benefited from the Core2disk-III residential program of Institut Pascal at Université Paris-Saclay, with the support of the program “Investissements d’avenir” ANR-11-IDEX-0003-01. This paper makes use of the following ALMA data: ADS/JAO.ALMA#2019.1.01813.S, ADS/JAO.ALMA#2019.1.00951.S, ADS/JAO.ALMA#2022.1.00126.S. ALMA is a partnership of ESO (representing its member states), NSF (USA) and NINS (Japan), together with NRC (Canada), MOST and ASIAA (Taiwan), and KASI (Republic of Korea), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO and NAOJ. We thank the entire ALMA team for their dedication to provide us with the data we used for this work. We thank Nicolas Cuello for helpful insights and discussion. We thank the referee for their insightful comments, which helped us to improve the quality of this work. M.K. acknowledges funding from the European Union’s Framework Programme for Research and Innovation Horizon 2020 (2014–2020) under the Marie Skłodowska-Curie Grant Agreement No. 897524 and funding from the Carlsberg foundation (grant number: CF22-1014).

Appendix A Datasets

We report a summary of the datasets used in this work in Table A.1.

Table A.1

Summary of the datasets.

Appendix B Modeling the compact emission

In order to measure α and β along the streamer free of flux contamination from the inner optically thick region, we subtracted the compact contribution centered on the source in two ways.

First, we fit a Gaussian model to the central region in the image plane. Figures B.1 and B.2 show the data, the model, and the residuals of the fit. Table B.1 summarizes the fitted parameters for the models in the two bands. The spectral index a and the spectral index of the dust opacity β were measured after the optically thick region was modeled out (Sect. 4). As a robustness check, we tested whether our results were robust against a different modeling scheme. We used the uvmodelfit CASA routine to fit a point-source component to the visibilities because the disc is unresolved at the resolution of our observations. The function fits for an offset from the phase center and the flux of the point source. We find the same offset from the center as for the Gaussian fit and a total integrated flux density of 16.1 mJy in B6 and 2.6 mJy in B3. We then subtracted this contribution from the visibility amplitudes (A=Re2+Im2)$\left( {{\rm{A}} = \sqrt {R{e^2} + I{m^2}} } \right)$ at all scales, and we binned them. In each bin, the uncertainty is given by the combined uncertainties on the real and imaginary parts of the visibilities, together with the ALMA calibration error (1σ = 5%, Remijan et al. 2019). We finally computed the spectral and dust opacity indices using Eqs. (1) and (3) as a function of uv distance after the subtraction, as shown in Fig. B.3. The bump at the short uv distances is caused by the combination of the asymmetric shape of the streamer with the uv coverage of the observations. The large scatter in amplitude at these scales also causes a larger error around the mean, and thus, a larger uncertainty on α and β. The very first bin (at the shortest common uv distance) shows β ~ 2 because of an increase in the B6 visibility amplitudes that is not observed in B3 due to the uv coverage. Shorter baselines, and thus, observations on larger recoverable scales, are needed to measure β in the outskirts of the streamer more reliably. The higher β would still agree with the conclusion of small ISM-like grains. Finally, the two azimuthally averaged spectral indices are consistent with what was found in the image plane: αS = 3.1 ± 0.1, and β = 1.55 ± 0.05.

thumbnail Fig. B.1

Contour levels (white) of the Gaussian model on top of the ALMA B3 (100 GHz) data of M512 (left). The color bar reports the flux values of the original image. The residuals of the model are shown on the right, and their color bar lies in the same range of values as the original emission to facilitate the comparison.
thumbnail Fig. B.2

Same as Fig. B.1, but for B6 (230 GHz) data.
Table B.1

Results of the Gaussian fit to the compact unresolved region around M512.

thumbnail Fig. B.3

Spectral (orange) and dust opacity (violet) indices as measured across the probed uv distances after subtraction of a point-like source. The mean values α ~ 3.1 and β ~ 1.6 are consistent with what was found across the scale of the streamer in the image-plane analysis.

Appendix C Possible flyby candidates

We here note the presence of a class II young stellar object (α2–25µm = −1; Megeath et al. 2012) at a projected distance of 100″(41,000 au) from M512. This source, 2MASS J05401156-0730409, was studied in continuum by van Terwisga et al. (2022), who reported a integrated 1.3mm flux of 1.65 ± 0.06 mJy and a dust mass estimate of 8.1 ± 0.3 M⊕, assuming optically thin emission, a dust temperature of 20 K, and a dust absorption opacity of 2.3 cm2/g. Gaia DR3 Gaia Collaboration (2022) reported a parallax of 2.54 ± 0.18 for the latter, indicating that it lies at a distance consistent with M512 (but still different from it), whose Gaia DR3 parallax is 2.37 ± 0.12. The measured Gaia DR3 proper motion in declination of the secondary object is pmDec = −0.18 ± 0.15 mas/yr and the proper motion in right ascension is pmRA = 0.14 ± 0.16 mas/yr. M512 moves in the plane of the sky with pmDec = −0.50 ± 0.10 mas/yr and pmRA = 0.15 ± 0.11. Considering that the relative motion of the sources is −0.32 ± 0.18 mas/yr in declination and δpmRA = 0.01 ± 0.19 in right ascension, the relative proper motions are consistent with a close encounter of the two objects between 200 and 700 kyr ago (1σ range) in the plane of the sky. However, considering the error bars on the Gaia proper motion and parallax measurements, it is possible that no flyby occurred at all. We report the 2MASS sky map in Figure C.1.

The spatial scale and the timescale both yield major counterarguments for this scenario. For a disk with a size Rdisc that is perturbed by a star during a close encounter Rƒlyby ~ Rdisc, simulations suggest that the induced arc-like spirals would have a spatial extent of about three times Rdisc at most (see Cuello et al. (2019)). The streamer around M512, however, is 4,000 au or longer (depending on projection effects and interferometric filtering), and would require an unreasonably extended protoplanetary disk that we would have resolved with our observations. Additionally, even in the earliest case that is compatible with Gaia constraints, a close encounter could have occurred between 200-700kyr ago, within 1 sigma confidence. The typical freefall timescale tff∝r3/Gm${{\rm{t}}_{ff}} \propto \sqrt {{r^3}/Gm} $ for a particle that is infalling from 4,000 au onto a 0.15 M⊙ star is roughly 50 kyr, which means that the material should already have fallen onto the star. If the observed streamer were a flyby-induced spiral, its survival time would be a few times the orbital period at most at the outer edge of the disk (Smallwood et al. 2023). The arc would therefore have been dispersed in a few thousand years, which means that it is highly improbable that it would have been observed. Last, the derived masses for the streamer around M512 and its inner region suggest that a flyby should have stripped away a significant portion of the disk (see Sect. 5.2). Pfalzner et al. (2005) demonstrated that even encounters with a similar-mass object and with a periastron of about the disk radius would only strip up to about 50% of the mass of the perturbed disk4. Finally, we inspected ALMA archival data for this nearby source (ID 2019.1.01813.S) and found no evidence for extended emission.

thumbnail Fig. C.1

2MASS map of the surroundings of M512, whose arc extends westward. A young stellar object (2MASS J05401156-0730409) lies at a projected distance of approximately 41,000 au from M512. The Gaia DR3 mean proper motion components are overlaid as arrows, and their magnitude is reported in milliarcseconds per year. A close encounter might have occurred, but only a few hundred thousand years ago. Each box of the grid is 1’×1’.

As a cautionary argument, however, we note that flybys for which the stripped material has been observed in a structure exceeding three times Rdisc (RW Aur) and for which the re-circularization timescales seem to exceed a few thousand years (HV Tau and DO Tau) have been observed in Rodriguez et al. (2018) and Winter et al. (2018a), respectively. Overall, we suggest that a flyby of M512 on 2MASS J05401156-0730409 appears to be harder to reconcile with the observed extended and massive arc than the streamer scenario, but it cannot be completely ruled out at this stage.

References

  1. Akiyama, E., Vorobyov, E. I., Liu, H. B., et al. 2019, AJ, 157, 165 [NASA ADS] [CrossRef] [Google Scholar]
  2. ALMA Partnership (Brogan, C. L., et al.) 2015, ApJ, 808, L3 [Google Scholar]
  3. Alves, F. O., Cleeves, L. I., Girart, J. M., et al. 2020, ApJ, 904, L6 [NASA ADS] [CrossRef] [Google Scholar]
  4. Andrews, S. M., Rosenfeld, K. A., Kraus, A. L., & Wilner, D. J. 2013, ApJ, 771, 129 [Google Scholar]
  5. Ansdell, M., Williams, J. P., van der Marel, N., et al. 2016, ApJ, 828, 46 [Google Scholar]
  6. Ardila, D. R., Golimowski, D. A., Krist, J. E., et al. 2007, ApJ, 665, 512 [Google Scholar]
  7. Aspin, C., & Reipurth, B. 2003, AJ, 126, 2936 [NASA ADS] [CrossRef] [Google Scholar]
  8. Bae, J., Hartmann, L., & Zhu, Z. 2015, ApJ, 805, 15 [NASA ADS] [CrossRef] [Google Scholar]
  9. Ballering, N. P., & Eisner, J. A. 2019, AJ, 157, 144 [Google Scholar]
  10. Barge, P., & Sommeria, J. 1995, A&A, 295, L1 [NASA ADS] [Google Scholar]
  11. Beccari, G., Spezzi, L., De Marchi, G., et al. 2010, ApJ, 720, 1108 [NASA ADS] [CrossRef] [Google Scholar]
  12. Beckwith, S. V. W., & Sargent, A. I. 1991, ApJ, 381, 250 [NASA ADS] [CrossRef] [Google Scholar]
  13. Birnstiel, T., Dullemond, C. P., Zhu, Z., et al. 2018, ApJ, 869, L45 [CrossRef] [Google Scholar]
  14. Bonnell, I., & Bastien, P. 1992, ApJ, 401, L31 [Google Scholar]
  15. Bryant, E. M., Bayliss, D., & Van Eylen, V. 2023, MNRAS, 521, 3663 [CrossRef] [Google Scholar]
  16. Cabedo, V., Maury, A., Girart, J. M., & Padovani, M. 2021, A&A, 653, A166 [NASA ADS] [CrossRef] [EDP Sciences] [Google Scholar]
  17. Cabrit, S., Pety, J., Pesenti, N., & Dougados, C. 2006, A&A, 452, 897 [CrossRef] [EDP Sciences] [Google Scholar]
  18. Cacciapuoti, L., Macias, E., Maury, A. J., et al. 2023, A&A, 676, A4 [NASA ADS] [CrossRef] [EDP Sciences] [Google Scholar]
  19. Caratti o Garatti, A., Garcia Lopez, R., Antoniucci, S., et al. 2012, A&A, 538, A64 [NASA ADS] [CrossRef] [EDP Sciences] [Google Scholar]
  20. Cuello, N., Dipierro, G., Mentiplay, D., et al. 2019, MNRAS, 483, 4114 [Google Scholar]
  21. Cuello, N., Ménard, F., & Price, D. J. 2023, Eur. Phys. J. Plus, 138, 11 [NASA ADS] [CrossRef] [Google Scholar]
  22. Dai, F., Facchini, S., Clarke, C. J., & Haworth, T. J. 2015, MNRAS, 449, 1996 [Google Scholar]
  23. De Marchi, G., Beccari, G., & Panagia, N. 2013a, ApJ, 775, 68 [NASA ADS] [CrossRef] [Google Scholar]
  24. De Marchi, G., Panagia, N., Guarcello, M. G., & Bonito, R. 2013b, MNRAS, 435, 3058 [NASA ADS] [CrossRef] [Google Scholar]
  25. Dong, R., Liu, H. B., Cuello, N., et al. 2022, Nat. Astron., 6, 331 [NASA ADS] [CrossRef] [Google Scholar]
  26. Draine, B. T. 2006, ApJ, 636, 1114 [Google Scholar]
  27. Dullemond, C. P., Küffmeier, M., Goicovic, F., et al. 2019, A&A, 628, A20 [NASA ADS] [CrossRef] [EDP Sciences] [Google Scholar]
  28. Fiorellino, E., Manara, C. F., Nisini, B., et al. 2021, A&A, 650, A43 [NASA ADS] [CrossRef] [EDP Sciences] [Google Scholar]
  29. Flores, C., Ohashi, N., Tobin, J. J., et al. 2023, ApJ, 958, 98 [NASA ADS] [CrossRef] [Google Scholar]
  30. Flores-Rivera, L., Terebey, S., Willacy, K., et al. 2021, ApJ, 908, 108 [NASA ADS] [CrossRef] [Google Scholar]
  31. Gaia Collaboration (Klioner, S. A., et al.) 2022, A&A, 667, A148 [NASA ADS] [CrossRef] [EDP Sciences] [Google Scholar]
  32. Galametz, M., Maury, A. J., Valdivia, V., et al. 2019, A&A, 632, A5 [NASA ADS] [CrossRef] [EDP Sciences] [Google Scholar]
  33. Garufi, A., Podio, L., Codella, C., et al. 2021, A&A, 645, A145 [EDP Sciences] [Google Scholar]
  34. Garufi, A., Podio, L., Codella, C., et al. 2022, A&A, 658, A104 [CrossRef] [EDP Sciences] [Google Scholar]
  35. Ginsburg, A., Robitaille, T., & Beaumont, C. 2016, Astrophysics Source Code Library [record ascl:1600.010] [Google Scholar]
  36. Ginski, C., Facchini, S., Huang, J., et al. 2021, ApJ, 908, L25 [NASA ADS] [CrossRef] [Google Scholar]
  37. Grady, C. A., Woodgate, B., Bruhweiler, F. C., et al. 1999, ApJ, 523, L151 [NASA ADS] [CrossRef] [Google Scholar]
  38. Grant, S. L., Espaillat, C. C., Wendeborn, J., et al. 2021, ApJ, 913, 123 [NASA ADS] [CrossRef] [Google Scholar]
  39. Gupta, A., Miotello, A., Manara, C. F., et al. 2023, A&A, 670, L8 [NASA ADS] [CrossRef] [EDP Sciences] [Google Scholar]
  40. Gupta, A., Miotello, A., Williams, J. P., et al. 2024, arXiv e-prints [arXiv:2401.10403] [Google Scholar]
  41. Gutermuth, R. A., Pipher, J. L., Megeath, S. T., et al. 2011, ApJ, 739, 84 [Google Scholar]
  42. Haworth, T. J. 2021, MNRAS, 503, 4172 [NASA ADS] [CrossRef] [Google Scholar]
  43. Hennebelle, P., Lesur, G., & Fromang, S. 2017, A&A, 599, A86 [NASA ADS] [CrossRef] [EDP Sciences] [Google Scholar]
  44. Hildebrand, R. H. 1983, QJRAS, 24, 267 [NASA ADS] [Google Scholar]
  45. Högbom, J. A. 1974, A&AS, 15, 417 [Google Scholar]
  46. Houge, A., & Krijt, S. 2023, MNRAS, 521, 5826 [NASA ADS] [CrossRef] [Google Scholar]
  47. Hsieh, C.-H., Arce, H. G., Li, Z.-Y., et al. 2023, ApJ, 947, 25 [NASA ADS] [CrossRef] [Google Scholar]
  48. Hunter, T. R., Indebetouw, R., Brogan, C. L., et al. 2023, PASP, 135, 074501 [NASA ADS] [CrossRef] [Google Scholar]
  49. Kenyon, S. J., Hartmann, L., & Hewett, R. 1988, ApJ, 325, 231 [NASA ADS] [CrossRef] [Google Scholar]
  50. Kuffmeier, M., Frimann, S., Jensen, S. S., & Haugbølle, T. 2018, MNRAS, 475, 2642 [NASA ADS] [CrossRef] [Google Scholar]
  51. Kuffmeier, M., Goicovic, F. G., & Dullemond, C. P. 2020, A&A, 633, A3 [NASA ADS] [CrossRef] [EDP Sciences] [Google Scholar]
  52. Kuffmeier, M., Dullemond, C. P., Reissl, S., & Goicovic, F. G. 2021, A&A, 656, A161 [NASA ADS] [CrossRef] [EDP Sciences] [Google Scholar]
  53. Kuffmeier, M., Jensen, S. S., & Haugbølle, T. 2023, Eur. Phys. J. Plus, 138, 272 [NASA ADS] [CrossRef] [Google Scholar]
  54. Kurtovic, N. T., Pérez, L. M., Benisty, M., et al. 2018, ApJ, 869, L44 [Google Scholar]
  55. Kuznetsova, A., Bae, J., Hartmann, L., & Mac Low, M.-M. 2022, ApJ, 928, 92 [NASA ADS] [CrossRef] [Google Scholar]
  56. Kwon, W., Looney, L. W., Mundy, L. G., Chiang, H.-F., & Kemball, A. J. 2009, ApJ, 696, 841 [NASA ADS] [CrossRef] [Google Scholar]
  57. Le Gouellec, V. J. M., Hull, C. L. H., Maury, A. J., et al. 2019, ApJ, 885, 106 [NASA ADS] [CrossRef] [Google Scholar]
  58. Le Gouellec, V. J. M., Maury, A. J., & Hull, C. L. H. 2023, A&A, 671, A167 [NASA ADS] [CrossRef] [EDP Sciences] [Google Scholar]
  59. Lebreuilly, U., Hennebelle, P., Colman, T., et al. 2021, ApJ, 917, L10 [NASA ADS] [CrossRef] [Google Scholar]
  60. Lebreuilly, U., Mac Low, M. M., Commerçon, B., & Ebel, D. S. 2023, A&A, 675, A38 [NASA ADS] [CrossRef] [EDP Sciences] [Google Scholar]
  61. Liu, H. B. 2019, ApJ, 877, L22 [NASA ADS] [CrossRef] [Google Scholar]
  62. Liu, B., Lambrechts, M., Johansen, A., Pascucci, I., & Henning, T. 2020, A&A, 638, A88 [EDP Sciences] [Google Scholar]
  63. Macías, E., Guerra-Alvarado, O., Carrasco-González, C., et al. 2021, A&A, 648, A33 [EDP Sciences] [Google Scholar]
  64. Manara, C. F., Morbidelli, A., & Guillot, T. 2018, A&A, 618, L3 [NASA ADS] [CrossRef] [EDP Sciences] [Google Scholar]
  65. Mathis, J. S., Rumpl, W., & Nordsieck, K. H. 1977, ApJ, 217, 425 [Google Scholar]
  66. Maury, A. J., Girart, J. M., Zhang, Q., et al. 2018, MNRAS, 477, 2760 [Google Scholar]
  67. Megeath, S. T., Gutermuth, R., Muzerolle, J., et al. 2012, AJ, 144, 192 [NASA ADS] [CrossRef] [Google Scholar]
  68. Ménard, F., Cuello, N., Ginski, C., et al. 2020, A&A, 639, A1 [NASA ADS] [CrossRef] [EDP Sciences] [Google Scholar]
  69. Mendoza, S., Tejeda, E., & Nagel, E. 2009, MNRAS, 393, 579 [NASA ADS] [CrossRef] [Google Scholar]
  70. Menten, K. M., Reid, M. J., Forbrich, J., & Brunthaler, A. 2007, A&A, 474, 515 [NASA ADS] [CrossRef] [EDP Sciences] [Google Scholar]
  71. Min, M., Rab, C., Woitke, P., Dominik, C., & Ménard, F. 2016, A&A, 585, A13 [NASA ADS] [CrossRef] [EDP Sciences] [Google Scholar]
  72. Miotello, A., Testi, L., Lodato, G., et al. 2014, A&A, 567, A32 [NASA ADS] [CrossRef] [EDP Sciences] [Google Scholar]
  73. Miyake, K., & Nakagawa, Y. 1993, Icarus, 106, 20 [NASA ADS] [CrossRef] [Google Scholar]
  74. Morales, J. C., Mustill, A. J., Ribas, I., et al. 2019, Science, 365, 1441 [Google Scholar]
  75. Motte, F., & André, P. 2001, A&A, 365, 440 [NASA ADS] [CrossRef] [EDP Sciences] [Google Scholar]
  76. Mulders, G. D., Pascucci, I., Ciesla, F. J., & Fernandes, R. B. 2021, ApJ, 920, 66 [NASA ADS] [CrossRef] [Google Scholar]
  77. Nakajima, T., & Golimowski, D. A. 1995, AJ, 109, 1181 [NASA ADS] [CrossRef] [Google Scholar]
  78. Natta, A., Testi, L., Calvet, N., et al. 2007, in Protostars and Planets V, eds. B. Reipurth, D. Jewitt, & K. Keil, 767 [Google Scholar]
  79. Offner, S. S. R., Moe, M., Kratter, K. M., et al. 2023, Protostars and Planets VII, ASP Conf. Ser., 534, eds. S.-i. Inutsuka, Y. Aikawa, T. Muto, K. Tomida, & M. Tamura (San Francisco: ASP), 275 [NASA ADS] [Google Scholar]
  80. Ormel, C. W., Paszun, D., Dominik, C., & Tielens, A. G. G. M. 2009, A&A, 502, 845 [NASA ADS] [CrossRef] [EDP Sciences] [Google Scholar]
  81. Owen, J. E., & Jacquet, E. 2014, MNRAS, 446, 3285 [Google Scholar]
  82. Padoan, P., Kritsuk, A., Norman, M. L., & Nordlund, Å. 2005, ApJ, 622, L61 [NASA ADS] [CrossRef] [Google Scholar]
  83. Padoan, P., Haugbølle, T., & Nordlund, Å. 2014, ApJ, 797, 32 [Google Scholar]
  84. Park, W., Lee, J.-E., Contreras Peña, C., et al. 2021, ApJ, 920, 132 [NASA ADS] [CrossRef] [Google Scholar]
  85. Pascucci, I., Testi, L., Herczeg, G. J., et al. 2016, ApJ, 831, 125 [Google Scholar]
  86. Pfalzner, S. 2013, A&A, 549, A82 [NASA ADS] [CrossRef] [EDP Sciences] [Google Scholar]
  87. Pfalzner, S., Vogel, P., Scharwächter, J., & Olczak, C. 2005, A&A, 437, 967 [CrossRef] [EDP Sciences] [Google Scholar]
  88. Pineda, J. E., Segura-Cox, D., Caselli, P., et al. 2020, Nat. Astron., 4, 1158 [NASA ADS] [CrossRef] [Google Scholar]
  89. Pineda, J. E., Arzoumanian, D., André, P., et al. 2023, Protostars and Planets VII, ASP Conf. Ser., 534, eds. S.-i. Inutsuka, Y. Aikawa, T. Muto, K. Tomida, & M. Tamura (San Francisco: ASP), 233 [NASA ADS] [Google Scholar]
  90. Pollack, J. B., Hollenbach, D., Beckwith, S., et al. 1994, ApJ, 421, 615 [Google Scholar]
  91. Remijan, A., Biggs, A., Cortes, P. A., et al. 2019, ALMA Technical Handbook, ALMA Doc. 7.3, ver. 1.1 [Google Scholar]
  92. Ribas, Á., Espaillat, C. C., Macías, E., & Sarro, L. M. 2020, A&A, 642, A171 [NASA ADS] [CrossRef] [EDP Sciences] [Google Scholar]
  93. Ricci, L., Testi, L., Natta, A., & Brooks, K. J. 2010, A&A, 521, A66 [NASA ADS] [CrossRef] [EDP Sciences] [Google Scholar]
  94. Rilinger, A. M., Espaillat, C. C., Xin, Z., et al. 2023, ApJ, 944, 66 [NASA ADS] [CrossRef] [Google Scholar]
  95. Rodriguez, J. E., Loomis, R., Cabrit, S., et al. 2018, ApJ, 859, 150 [Google Scholar]
  96. Sanchis, E., Testi, L., Natta, A., et al. 2020, A&A, 633, A114 [NASA ADS] [CrossRef] [EDP Sciences] [Google Scholar]
  97. Scholz, A., Froebrich, D., & Wood, K. 2013, MNRAS, 430, 2910 [Google Scholar]
  98. Scicluna, P., Rosotti, G., Dale, J. E., & Testi, L. 2014, A&A, 566, L3 [NASA ADS] [CrossRef] [EDP Sciences] [Google Scholar]
  99. Segura-Cox, D. M., Schmiedeke, A., Pineda, J. E., et al. 2020, Nature, 586, 228 [NASA ADS] [CrossRef] [Google Scholar]
  100. Smallwood, J. L., Yang, C.-C., Zhu, Z., et al. 2023, MNRAS, 521, 3500 [NASA ADS] [CrossRef] [Google Scholar]
  101. Steinacker, J., Pagani, L., Bacmann, A., & Guieu, S. 2010, A&A, 511, A9 [NASA ADS] [CrossRef] [EDP Sciences] [Google Scholar]
  102. Steinacker, J., Ormel, C. W., Andersen, M., & Bacmann, A. 2014, A&A, 564, A96 [EDP Sciences] [Google Scholar]
  103. Steinacker, J., Andersen, M., Thi, W. F., et al. 2015, A&A, 582, A70 [NASA ADS] [CrossRef] [EDP Sciences] [Google Scholar]
  104. Testi, L., Birnstiel, T., Ricci, L., et al. 2014, in Protostars and Planets VI, eds. H. Beuther, R. S. Klessen, C. P. Dullemond, & T. Henning, 339 [Google Scholar]
  105. Testi, L., Natta, A., Scholz, A., et al. 2016, A&A, 593, A111 [NASA ADS] [CrossRef] [EDP Sciences] [Google Scholar]
  106. Thies, I., Kroupa, P., Goodwin, S. P., Stamatellos, D., & Whitworth, A. P. 2011, MNRAS, 417, 1817 [NASA ADS] [CrossRef] [Google Scholar]
  107. Throop, H. B., & Bally, J. 2008, AJ, 135, 2380 [NASA ADS] [CrossRef] [Google Scholar]
  108. Tobin, J. J., Hartmann, L., Looney, L. W., & Chiang, H.-F. 2010, ApJ, 712, 1010 [CrossRef] [Google Scholar]
  109. Tychoniec, L., Manara, C. F., Rosotti, G. P., et al. 2020, A&A, 640, A19 [NASA ADS] [CrossRef] [EDP Sciences] [Google Scholar]
  110. Valdivia-Mena, M. T., Pineda, J. E., Segura-Cox, D. M., et al. 2022, A&A, 667, A12 [NASA ADS] [CrossRef] [EDP Sciences] [Google Scholar]
  111. Valdivia-Mena, M. T., Pineda, J. E., Segura-Cox, D. M., et al. 2023, A&A, 677, A92 [NASA ADS] [CrossRef] [EDP Sciences] [Google Scholar]
  112. van Terwisga, S. E., & Hacar, A. 2023, A&A, 673, L2 [CrossRef] [EDP Sciences] [Google Scholar]
  113. van Terwisga, S. E., Hacar, A., van Dishoeck, E. F., Oonk, R., & Portegies Zwart, S. 2022, A&A, 661, A53 [NASA ADS] [CrossRef] [EDP Sciences] [Google Scholar]
  114. Weingartner, J. C., & Draine, B. T. 2001, ApJ, 548, 296 [Google Scholar]
  115. Wiebe, D. S., Molyarova, T. S., Akimkin, V. V., Vorobyov, E. I., & Semenov, D. A. 2019, MNRAS, 485, 1843 [Google Scholar]
  116. Williams, J. P., Cieza, L., Hales, A., et al. 2019, ApJ, 875, L9 [Google Scholar]
  117. Winter, A. J., Booth, R. A., & Clarke, C. J. 2018a, MNRAS, 479, 5522 [Google Scholar]
  118. Winter, A. J., Clarke, C. J., Rosotti, G., et al. 2018b, MNRAS, 475, 2314 [CrossRef] [Google Scholar]
  119. Xin, Z., Espaillat, C. C., Rilinger, A. M., Ribas, Á., & Macías, E. 2023, ApJ, 942, 4 [NASA ADS] [CrossRef] [Google Scholar]
  120. Yen, H.-W., Takakuwa, S., Ohashi, N., et al. 2014, ApJ, 793, 1 [NASA ADS] [CrossRef] [Google Scholar]
  121. Yen, H.-W., Gu, P.-G., Hirano, N., et al. 2019, ApJ, 880, 69 [NASA ADS] [CrossRef] [Google Scholar]
  122. Zhu, Z., Zhang, S., Jiang, Y.-F., et al. 2019, ApJ, 877, L18 [NASA ADS] [CrossRef] [Google Scholar]
1

However, M512 lays in a region where the UV irradiation field is too low to induce such an effect (van Terwisga & Hacar 2023).

2

The typical duration interval between subsequent outbursts for FUOr events (Scholz et al. 2013).

3

This value is obtained when considering the opacities for ISM-like grains of Birnstiel et al. (2018), thus ĸ1.3mm = 0.4 g cm−2, and the temperature profile give in Eq. (2).

4

Although this argument relies on the systematically uncertain dustmass constraints.

All Tables

Table 1

Stellar parameters of M512 as reported by Caratti o Garatti et al. (2012), based on its spectral energy distribution and SofI near-infrared spectra.

In the text
Table A.1

Summary of the datasets.

In the text
Table B.1

Results of the Gaussian fit to the compact unresolved region around M512.

In the text

All Figures

thumbnail Fig. 1

ALMA Band 3 (100 GHz) continuum emission of M512 with [3, 7, 100]σ contours overplotted in white (left). ALMA Band 6 (230 GHz) with [3, 10, 100]σ contours overplotted in white (center). The spectral index as measured from Eq. (1) using only pixels with flux above the 3σ noise level (right). The x- and y-axes report the offset from the central source in arcseconds. The color bars represent the flux density (mJy beam−1) for the ALMA observations (left, center) and the value of the spectral index (right). The images have been created applying a uv taper to the visibilities, with Briggs weighting and robust = 1. Then we have smoothed them to the same resolution of 1″.6, which is roughly the width of the extended emission. The beam is reported in the lower left corner.
In the text
thumbnail Fig. 2

Moment-one map of the 18CO J = 2−1 transition (>2σ) around M512 (left). The black contours are the B6 continuum [3, 10, 100]σ levels. The green line is the TIPSY model trajectory for M = 0.15 M⊙ and vsys = 3.25 km s−1. The position-velocity diagram of the streamer emission (grey contours) is extracted along the TIPSY trajectory and includes the inner protostellar region (right). The TIPSY fit to the radial velocities is reported as a green line.
In the text
thumbnail Fig. 3

Same as Fig. 1, but after subtraction of the inner optically thick region. Only the pixels with flux above 3σ are shown for each inset.
In the text
thumbnail Fig. 4

Profile of the spectral index β of the dust opacity along the length of the streamer. The approximation β = α − 2 is shown as the orange line, and β, corrected for the deviation from the RJ approximation, is shown as the violet line. This profile has been obtained starting from the maps in Fig. 3, where the central emission had been modeled and subtracted. The centers of the selected apertures in which we derive β are highlighted in white among all the points that sample the manually defined logarithmic spiral in the B6 map as an example (upper inset). Throughout the whole structure, β ~ 1.6. The gray band represents ISM-like β.
In the text
thumbnail Fig. B.1

Contour levels (white) of the Gaussian model on top of the ALMA B3 (100 GHz) data of M512 (left). The color bar reports the flux values of the original image. The residuals of the model are shown on the right, and their color bar lies in the same range of values as the original emission to facilitate the comparison.
In the text
thumbnail Fig. B.2

Same as Fig. B.1, but for B6 (230 GHz) data.
In the text
thumbnail Fig. B.3

Spectral (orange) and dust opacity (violet) indices as measured across the probed uv distances after subtraction of a point-like source. The mean values α ~ 3.1 and β ~ 1.6 are consistent with what was found across the scale of the streamer in the image-plane analysis.
In the text
thumbnail Fig. C.1

2MASS map of the surroundings of M512, whose arc extends westward. A young stellar object (2MASS J05401156-0730409) lies at a projected distance of approximately 41,000 au from M512. The Gaia DR3 mean proper motion components are overlaid as arrows, and their magnitude is reported in milliarcseconds per year. A close encounter might have occurred, but only a few hundred thousand years ago. Each box of the grid is 1’×1’.
In the text

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