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J/A+A/606/A121      NGC1333 IRAS 4A ALMA and PdBI maps   (Lopez-Sepulcre+, 2017)

Complex organics in IRAS 4A revisited with ALMA: Striking contrast between two neighbouring protostellar cores. Lopez-Sepulcre A., Sakai N., Neri R., Imai M., Oya Y., Ceccarelli C., Higuchi A., Aikawa Y., Bottinelli S., Caux E., Hirota T., Kahane C., Lefloch B., Vastel C., Watanabe Y., Yamamoto S. <Astron. Astrophys. 606, A121 (2017)> =2017A&A...606A.121L (SIMBAD/NED BibCode)
ADC_Keywords: Infrared sources ; Radio lines Keywords: astrochemistry - stars: formation - ISM: abundances - ISM: individual objects: NGC1333 IRAS 4A Abstract: Hot corinos are extremely rich in complex organic molecules (COMs). Accurate abundance measurements of COMs in such objects are crucial to constrain astrochemical models. In the particular case of close binary systems this can only be achieved through high angular resolution imaging. We aim to perform an interferometric study of multiple COMs in NGC1333 IRAS 4A, which is a protostellar binary hosting hot corino activity, at an angular resolution that is sufficient to distinguish easily the emission from the two cores separated by 1.8". We used the Atacama Large (sub-)Millimeter Array (ALMA) in its 1.2mm band and the IRAM Plateau de Bure Interferometer (PdBI) at 2.7mm to image, with an angular resolution of 0.5" (120au) and 1" (235au), respectively, the emission from 11 different organic molecules in IRAS 4A. This allowed us to clearly disentangle A1 and A2, the two protostellar cores. For the first time, we were able to derive the column densities and fractional abundances simultaneously for the two objects, allowing us to analyse the chemical differences between them. Molecular emission from organic molecules is concentrated exclusively in A2, while A1 appears completely devoid of COMs or even simpler organic molecules, such as HNCO, even though A1 is the strongest continuum emitter. The protostellar core A2 displays typical hot corino abundances and its deconvolved size is 70au. In contrast, the upper limits we placed on COM abundances for A1 are extremely low, lying about one order of magnitude below prestellar values. The difference in the amount of COMs present in A1 and A2 ranges between one and two orders of magnitude. Our results suggest that the optical depth of dust emission at these wavelengths is unlikely to be sufficiently high to completely hide a hot corino in A1 similar in size to that in A2. Thus, the significant contrast in molecular richness found between the two sources is most probably real. We estimate that the size of a hypothetical hot corino in A1 should be less than 12 au. Our results favour a scenario in which the protostar in A2 is either more massive and/or subject to a higher accretion rate than A1, as a result of inhomogeneous fragmentation of the parental molecular clump. This naturally explains the smaller current envelope mass in A2 with respect to A1 along with its molecular richness. The extremely low abundances of organic molecules in A1 with respect to those in A2 demonstrate that the dense inner regions of a young protostellar core lacking hot corino activity may be poorer in COMs than the outer protostellar envelope. Description: The Atacama Large (sub-)Millimeter Array (ALMA) was used on 14 June 2014, in its Cycle 2 operations, to observe IRAS 4A in Band 6 (∼250GHz). A total of 35 antennas of the 12m array were used with a minimum and maximum baseline length of 18m and 784m, respectively. The phase centre of the observation was RA=03:29:10.51, DE=+31:13:31.3 (J2000) and the total integration time onsource was 26-min. The PdBI was used on 29 January 2005 in its A configuration to observe IRAS 4A at 2.7mm. The baselines ranged from 32 to 400m. The phase centre of the observations was RA=03:29:10.30, DE=+31:13:31.0 (J2000). Objects: ------------------------------------------------------ RA (2000) DE Designation(s) ------------------------------------------------------ 03 29 10.49 +31 13 30.8 IRAS 4A = [JCC87] IRAS 4A ------------------------------------------------------ File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file list.dat 116 18 List of fits maps fits/* 0 18 Individual fits maps
See also: J/A+A/558/A58 : NGC 1333-IRAS 4A C18O, NO and O2 spectra (Yildiz+, 2013) J/A+A/568/A125 : NGC 1333 IRAS 4A H2O observations (Santangelo+, 2014) Byte-by-byte Description of file: list.dat
Bytes Format Units Label Explanations
1- 9 F9.5 deg RAdeg Right Ascension of center (J2000) 10- 18 F9.5 deg DEdeg Declination of center (J2000) 20- 23 I4 --- Nx Number of pixels along X-axis 25- 28 I4 --- Ny Number of pixels along Y-axis 30- 31 I2 mJy/beam.km/s RMS ? Root mean square (RMS) noise level 33- 36 F4.2 arcsec Beam1 ? Beam size 37 A1 --- --- [x] 38- 41 F4.2 arcsec Beam2 ? Beam size 43- 46 I4 deg PA []? Position angle 48- 51 I4 Kibyte size Size of FITS file 53- 64 A12 --- FileName Name of FITS file, in subdirectory fits 66-116 A51 --- Title Title of the FITS file
Acknowledgements: Ana Lopez-Sepulcre, lopez(at)iram.fr
(End) Patricia Vannier [CDS] 13-Jul-2017
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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