Issue |
A&A
Volume 672, April 2023
|
|
---|---|---|
Article Number | A158 | |
Number of page(s) | 19 | |
Section | Interstellar and circumstellar matter | |
DOI | https://doi.org/10.1051/0004-6361/202244911 | |
Published online | 17 April 2023 |
The Effelsberg survey of FU Orionis and EX Lupi objects
I. Host environments of FUors and EXors traced by NH3★
1
Max-Planck-Institut für Radioastronomie,
Auf dem Hügel 69,
53121
Bonn,
Germany
e-mail: zszabo@mpifr-bonn.mpg.de
2
Scottish Universities Physics Alliance (SUPA), School of Physics and Astronomy, University of St Andrews, North Haugh,
St Andrews,
KY16 9SS,
UK
3
Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, Eötvös Loránd Research Network (ELKH),
Konkoly-Thege Miklós út 15–17,
1121
Budapest,
Hungary
4
CSFK, MTA Centre of Excellence,
Konkoly Thege Miklós út 15–17,
1121
Budapest,
Hungary
5
ELTE Eötvös Loránd University, Institute of Physics,
Pázmány Péter sétány 1/A,
1117
Budapest,
Hungary
6
Max-Planck-Institut für Astronomie,
Königstuhl 17,
69117
Heidelberg,
Germany
Received:
7
September
2022
Accepted:
6
February
2023
Context. FU Orionis (FUor) and EX Lupi (EXor) type objects represent two small but rather spectacular groups of low-mass, young, eruptive stars. In both cases, outbursts of several magnitudes are observed, which are attributed to enhanced mass accretion from the circumstellar disc onto the central protostar. Although these objects are well studied at optical and near-infrared wavelengths, their host molecular environments are poorly explored because of the scarcity of systematic molecular line observations.
Aims. We aim to carry out the first dedicated survey of the molecular environments of a large sample of FUors and EXors, observing a total of 51 sources, including some Gaia alerts, to study the ammonia (NH3) emission in their host environments.
Methods. We observed the ammonia (J, K) = (1,1), (2,2), and (3,3) inversion transitions at ~23.7 GHz in position-switching mode using the Effelsberg 100-m radio telescope. For 19 of the 51 sources in our sample, we derived H2 column densities and dust temperatures using archival Herschel/SPIRE data at 250 µm, 300 µm, and 500 µm.
Results. We detected the NH3 (1,1) transition toward 28 sources and the (2,2) transition toward 12 sources, while the (3,3) transition was detected towards only two sources in our sample. We find kinetic temperatures between ~12 K and 21 K, ammonia column densities from 5.2 × 1013 cm−2 to 3.2 × 1015 cm−2, and fractional ammonia abundances with respect to H2 from 4.7 × 10−9 to 1.5 × 10−7. These results are comparable to those found in infrared dark clouds (IRDCs). Our kinematic analysis suggests that most of the eruptive stars in our sample reside in rather quiescent (sonic or transonic) host environments.
Conclusions. Our NH3 observations and analysis of the SPIRE dust-based H2 column density maps confirm the presence of dense material towards seven sources in our sample; additional sources might also harbour dense gas based on their NH2 (2,2) detections, potentially indicating an earlier phase than originally classified. Based on our results, we suggest that observations targeting additional molecular lines would help to refine the evolutionary classification of eruptive stars.
Key words: molecular data / methods: observational / stars: low-mass / stars: pre-main sequence / radio lines: ISM / stars: formation
Full Fig. 1 and FITS files for the NH3 detections are available at https://zenodo.org/record/7736131
© The Authors 2023
Open 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.
This article is published in open access under the Subscribe to Open model.
Open Access funding provided by Max Planck Society.
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