2013A&A...558A..58Y


C.D.S. - SIMBAD4 rel 1.7 - 2019.09.16CEST19:31:27

2013A&A...558A..58Y - Astronomy and Astrophysics, volume 558A, 58-58 (2013/10-1)

Deep observations of O2 toward a low-mass protostar with Herschel-HIFI.

YILDIZ U.A., ACHARYYA K., GOLDSMITH P.F., VAN DISHOECK E.F., MELNICK G., SNELL R., LISEAU R., CHEN J.-H., PAGANI L., BERGIN E., CASELLI P., HERBST E., KRISTENSEN L.E., VISSER R., LIS D.C. and GERIN M.

Abstract (from CDS):

According to traditional gas-phase chemical models, O2 should be abundant in molecular clouds, but until recently, attempts to detect interstellar O2 line emission with ground- and space-based observatories have failed. Following the multi-line detections of O2 with low abundances in the Orion and ρ Oph A molecular clouds with Herschel, it is important to investigate other environments, and we here quantify the O2 abundance near a solar-mass protostar. Observations of molecular oxygen, O2, at 487 GHz toward a deeply embedded low-mass Class 0 protostar, NGC 1333-IRAS 4A, are presented, using the Heterodyne Instrument for the Far Infrared (HIFI) on the Herschel Space Observatory. Complementary data of the chemically related NO and CO molecules are obtained as well. The high spectral resolution data are analysed using radiative transfer models to infer column densities and abundances, and are tested directly against full gas-grain chemical models. The deep HIFI spectrum fails to show O2 at the velocity of the dense protostellar envelope, implying one of the lowest abundance upper limits of O2/H2 at ≤6x10–9 (3σ). The O2/CO abundance ratio is less than 0.005. However, a tentative (4.5σ) detection of O2 is seen at the velocity of the surrounding NGC 1333 molecular cloud, shifted by 1km/s relative to the protostar. For the protostellar envelope, pure gas-phase models and gas-grain chemical models require a long pre-collapse phase (∼0.7-1x106 years), during which atomic and molecular oxygen are frozen out onto dust grains and fully converted to H2O, to avoid overproduction of O2 in the dense envelope. The same model also reproduces the limits on the chemically related NO molecule if hydrogenation of NO on the grains to more complex molecules such as NH2OH, found in recent laboratory experiments, is included. The tentative detection of O2 in the surrounding cloud is consistent with a low-density PDR model with small changes in reaction rates. The low O2 abundance in the collapsing envelope around a low-mass protostar suggests that the gas and ice entering protoplanetary disks is very poor in O2.

Abstract Copyright:

Journal keyword(s): astrochemistry - stars: formation - ISM: molecules - ISM: individual objects: NGC 1333 IRAS 4A

VizieR on-line data: <Available at CDS (J/A+A/558/A58): list.dat fits/*>

Simbad objects: 9

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Number of rows : 9

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2019
#notes
1 NGC 1333 SFR 03 28 55 +31 22.2   10.9       ~ 1177 1
2 [JCC87] IRAS 4A Y*O 03 29 10.49 +31 13 30.8           ~ 561 1
3 [JCC87] IRAS 4 FIR 03 29 10.9 +31 13 26           ~ 461 0
4 [JCC87] IRAS 4B Y*O 03 29 12.058 +31 13 02.05           ~ 543 0
5 BD+30 549 Y*O 03 29 19.7770675177 +31 24 57.044403187 10.81 10.95 10.47 10.587   B8:p 91 1
6 NAME Orion Bright Bar reg 05 35 22.30 -05 24 33.0           ~ 685 0
7 V* FU Dra WU* 15 34 45.2141461351 +62 16 44.330023737       10.1   G0: 112 1
8 * rho Oph A * 16 25 35.142 -23 26 49.90 4.3 5.22 5.05     B2/3V 378 0
9 NAME rho Oph A Cloud MoC 16 26 26.4 -24 22 33           ~ 235 1

    Equat.    Gal    SGal    Ecl

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2019.09.16-19:31:27

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