2 Observations

   
2.1 $\mathsfsl {Chandra}$ X-ray observations and data reduction

IRAS 19410+2336 was observed with the ACIS-S3 chip on board the X-ray telescope Chandra for 20 ksec on October 15 2001. The ACIS-S3 aim-point was centered at the IRAS position RA 19:43:11.4, Dec 23:44:06.0. (J2000.0) that is coincident with the main mm emission peak. The field of interest shown in Fig. 1 is much smaller than the $\sim$ $8'~ \times~ 8'$ field of view of the S3 chip, and the FWHM of the point-spread-function of this region is approximately 0.5''. The data were reduced with the CIAO 2.2 software package using the CALDB 2.10 database. Both packages are provided by the Chandra X-ray center. The basic data product of our observation is the level 2 processed event list provided by the pipeline processing at the Chandra X-ray center.

Light curves were extracted for the whole S3 chip as well as just for the region presented in Fig. 1. No flares or enhancements due to low energy protons are observed. The whole observation time is usable as good time interval. The background emission is about 0.1 cts pixel^-1, but as one or two photons could be detected by background fluctuations anyway, we conservatively use 6 cts as the detection threshold for an X-ray source in this field. A wavelet based source detection algorithm was applied using default parameters (Freeman et al. 2002), and 13 sources between 7 and 19 cts are found in the field of interest (Table 1). Based on the 1.2 mm continuum map from the 30 m telescope - assuming optically thin dust emission -, we can estimate an average hydrogen column density of $N_{\rm {H}}=5\times 10^{22}$ cm^-2 of the molecular cloud (for details on the dust emission see Beuther et al. 2002a). A Raymond-Smith plasma model (Raymond & Smith 1977) with a 3 keV plasma, which is commonly used to model the X-ray emission of very young and embedded pre-main-sequence sources (Feigelson & Montmerle 1999; Preibisch & Zinnecker 2002), 6 cts correspond to an unabsorbed flux limit of $2 \times 10^{-14}$ erg cm^-2 s^-1. Based on the $\log N$-$\log S$distribution of Giacconi et al. (2001), in a field as small as ours less than 0.1 extragalactic background sources are expected. The source positions in the field of interest are compared with 2MASS near-infrared data and should be correct within less than 1''.

2.2 Plateau de Bure mm observations

We observed IRAS 19410+2336 in Summer 2001 with the Plateau de Bure Interferometer (PdBI) at 2.6 mm in the D (with 4 antennas) and C (with 5 antennas) configuration (Guilloteau et al. 1992). The simultaneously observed 1 mm data were only used for phase corrections because of the poor Summer weather conditions. The 3 mm receivers were tuned to 115.27 GHz (USB) (centered at the ¹²CO $1\to0$ line) with a sideband rejection of about 5 dB. At this frequency, the typical SSB system temperature is 300 to 400 K, and the phase noise was below 30$^{\circ}$. Atmospheric phase correction based on the 1.3 mm total power was applied. For continuum measurements, we placed two 320 MHz correlator units in the band to cover the largest possible bandwidths. In this paper we are focusing on the 2.6 mm continuum data, the CO line observations will be presented elsewhere. Temporal fluctuations of the amplitude and phase were calibrated with frequent observations of the quasars 1923+210 and 2023+336. The amplitude scale was derived from measurements of MWC349 and CRL618, and we estimate the final flux density accuracy to be $\sim$15%. To cover both cores a mosaic of 10 fields was observed. The final beam size is  $4.1'' \times 3.6''$ (PA $-108^{\circ}$). We obtain a $3\sigma$ rms of $\sim$5 mJy, which corresponds to a mass sensitivity limit of approximately $15~M_{\odot}$ assuming optically thin dust emission at 2.6 mm (see, e.g., Beuther et al. 2002a for the deviation of dust parameters from mm observations).

   
2.3 Calar Alto near-infrared observations

The near-infrared camera Omega Prime on the 3.5 m telescope on Calar Alto/Spain was used to obtain $K^\prime$ wide field images of the region around IRAS 19410+2336 in June 2001. At a pixel scale of 0.4'' pixel^-1, the $1024\times1024$ pixel array provides a field-of-view of $\sim$ $6.8'~ \times~ 6.8'$. A five position dither pattern was applied to image the field and to allow for a correction of array defects that were identified from well illuminated flat-field frames (for the dark pixels) and a dark frame (for the hot pixels). In each dither position, 15 individual exposures of 2 s were stacked into one frame of 30 s total integration time. For each position, the thermal background (sky) was computed by median combining the four frames resulting from the other dither positions. This sky frame was subtracted from the respective science frame, which also removes the bias level. The resulting frame was divided by a flat-field resulting from dome flats (the difference of a number of frames of the dome illuminated by a tungsten lamp and a number of frames taken without illumination). The images of the various dither positions were then registered and averaged into the final image. The total integration time in the center of the final image is 2.5 min, which yields a detection limit ($5\sigma$ peak flux) for point sources of roughly $K^{\prime}=17.5$. The seeing-limited angular resolution in the final image is about 1.2''. Because the observation was conducted at high air-masses, its photometry is rather poor. Thus, we used the Omega Prime data for identification only, and the photometry is taken from the 2MASS catalog.