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J/A+A/613/A29       NGC1333-IRAS2A water snowline imaging   (van 't Hoff+, 2018)

Imaging the water snowline in a protostellar envelope with H13CO+. van 't Hoff M.L.R., Persson M.V., Harsono D., Taquet V., Jorgensen J.K., Visser R., Bergin E.A., van Dishoeck E.F. <Astron. Astrophys. 613, A29 (2018)> =2018A&A...613A..29V (SIMBAD/NED BibCode)
ADC_Keywords: YSOs ; Interstellar medium ; Millimetric/submm sources Keywords: ISM: individual objects: NGC1333-IRAS2A - ISM: molecules - astrochemistry - stars: protostars - submillimeter: planetary systems Abstract: Snowlines are key ingredients for planet formation. Providing observational constraints on the locations of the major snowlines is therefore crucial for fully connecting planet compositions to their formation mechanism. Unfortunately, the most important snowline, that of water, is very difficult to observe directly in protoplanetary disks due to its close proximity to the central star. Based on chemical considerations, HCO+ is predicted to be a good chemical tracer of the water snowline, because it is particularly abundant in dense clouds when water is frozen out. This work aims to map the optically thin isotopologue H13CO+ toward the envelope of the low-mass protostar NGC1333-IRAS2A, where the snowline is at larger distance from the star than in disks. Comparison with previous observations of H218O will show whether H13CO+ is indeed a good tracer of the water snowline. NGC1333-IRAS2A was observed using NOEMA at ∼0.9 arcsec resolution, targeting the H13CO+ J=3-2 transition at 260.255GHz. The integrated emission profile was analyzed using 1D radiative transfer modeling of a spherical envelope with a parametrized abundance profile for H13CO+. This profile was validated with a full chemical model. The H13CO+ emission peaks ∼2-arcsec northeast of the continuum peak, whereas H218O shows compact emission on source. Quantitative modeling shows that a decrease in H13CO+ abundance by at least a factor of six is needed in the inner ∼360AU to reproduce the observed emission profile. Chemical modeling predicts indeed a steep increase in HCO+ just outside the water snowline; the 50% decrease in gaseous H2O at the snowline is not enough to allow HCO+ to be abundant. This places the water snowline at 225AU, further away from the star than expected based on the 1D envelope temperature structure for NGC1333-IRAS2A. In contrast, DCO+ observations show that the CO snowline is at the expected location, making an outburst scenario unlikely. The spatial anticorrelation of the H13CO+ and H218O emission provide a proof of concept that H13CO+ can be used as a tracer of the water snowline. Description: Datacubes in fits format of the H13CO+, H218O and DCO+ emission imaged towards NGC1333-IRAS2A using the IRAM-NOEMA interferometer (see Figs. 1, 2, and 8). IRAS2A was observed at 260.255GHz (targeting H13CO+ J=3-2) on December 1, 2015 and April 9, 2016, covering baselines from 7m to 457m. The spectral resolution is 0.078MHz (0.09km/s). The H218O 3(1,3)-2(2,0) transition at 203.408GHz was observed in December 2009 and March 2010, with a spectral resolution 0.087MHz (0.115km/s). See Persson et al., 2012A&A...541A..39P. The DCO+ J=2-1 transition at 144.068GHz was observed as part of a larger study during July, August, November 2010 and March 2011 with a spectral resolution of 4km/s. Objects: ----------------------------------------------------------- RA (2000) DE Designation(s) ----------------------------------------------------------- 03 28 55.55 +31 14 36.7 NGC1333-IRAS2A = [JCC87] IRAS 2A ----------------------------------------------------------- File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file list.dat 113 3 List fo fits datacubes fits/* 0 3 Individual datacubes
See also: J/A+A/606/A121 : NGC1333 IRAS 4A ALMA and PdBI maps (Lopez-Sepulcre+, 2017) J/A+A/563/L2 : NGC1333-IRAS2A CALYPSO IRAM-PdBI 1mm maps (Maury+, 2014) J/A+A/563/L3 : NGC1333-IRAS2A CALYPSO IRAM-PdBI SiO & SO maps (Codella+ 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- 22 I3 --- Nx Number of pixels along X-axis 24- 26 I3 --- Ny Number of pixels along Y-axis 28- 30 I3 --- Nz Number of pixels along Z-axis 32- 41 F10.3 m/s bVRAD Lower value of VRAD interval 43- 49 F7.1 m/s BVRAD Upper value of VRAD interval 51- 59 F9.4 m/s dVRAD VRAD resolution 61- 66 I6 Kibyte size Size of FITS file 68- 78 A11 --- FileName Name of FITS file, in subdirectory fits 80-113 A34 --- Title Title of the FITS file
Acknowledgements: Merel van 't Hoff, vthoff(at)strw.leidenuniv.nl
(End) Patricia Vannier [CDS] 22-Feb-2018
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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