2014A&A...569A..19T


Query : 2014A&A...569A..19T

2014A&A...569A..19T - Astronomy and Astrophysics, volume 569A, 19-19 (2014/9-1)

Deuteration around the ultracompact HII region Monoceros R2.

TREVINO-MORALES S.P., PILLERI P., FUENTE A., KRAMER C., ROUEFF E., GONZALEZ-GARCIA M., CERNICHARO J., GERIN M., GOICOECHEA J.R., PETY J., BERNE O., OSSENKOPF V., GINARD D., GARCIA-BURILLO S., RIZZO J.R. and VITI S.

Abstract (from CDS):

The massive star-forming region Monoceros R2 (Mon R2) hosts the closest ultra-compact HII region, where the photon-dominated region (PDR) between the ionized and molecular gas can be spatially resolved with current single-dish telescopes. We aim at studying the chemistry of deuterated molecules toward Mon R2 to determine the deuterium fractions around a high-UV irradiated PDR and investigate the chemistry of these species. We used the IRAM-30m telescope to carry out an unbiased spectral survey toward two important positions (namely IF and MP2) in Mon R2 at 1, 2, and 3mm. This spectral survey is the observational basis of our study of the deuteration in this massive star-forming region. Our high spectral resolution observations (∼0.25-0.65km/s) allowed us to resolve the line profiles of the different species detected. We found a rich chemistry of deuterated species at both positions of Mon R2, with detections of C2D, DCN, DNC, DCO+, D2CO, HDCO, NH2D, and N2D+ and their corresponding hydrogenated species and rarer isotopologs. The high spectral resolution of our observations allowed us to resolve three velocity components: the component at 10km/s is detected at both positions and seems associated with the layer most exposed to the UV radiation from IRS 1; the component at 12km/s is found toward the IF position and seems related to the foreground molecular gas; finally, a component at 8.5km/s is only detected toward the MP2 position, most likely related to a low-UV irradiated PDR. We derived the column density of the deuterated species (together with their hydrogenated counterparts), and determined the deuterium fractions as Dfrac=[XD]/[XH]. The values of Dfrac are around 0.01 for all the observed species, except for HCO+ and N2H+, which have values 10 times lower. The values found in Mon R2 are similar to those measured in the Orion Bar, and are well explained with a pseudo-time-dependent gas-phase model in which deuteration occurs mainly via ion-molecule reactions with H2D+, CH2D+ and C2HD+. Finally, the H13CN/HN13C ratio is very high (∼11) for the 10km/s component, which also agree with our model predictions for an age of ∼0.01 to a few 0.1Myr. The deuterium chemistry is a good tool for studying the low-mass and high-mass star-forming regions. However, while low-mass star-forming regions seem well characterized with Dfrac(N2H+) or Dfrac(HCO+), a more complete chemical modeling is required to date massive star-forming regions. This is due to the higher gas temperature together with the rapid evolution of massive protostars.

Abstract Copyright:

Journal keyword(s): astrochemistry - HII regions - photon-dominated region (PDR) - radio lines: ISM

Simbad objects: 13

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Number of rows : 13
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2022
#notes
1 Barnard 1 MoC 03 33 16.3 +31 07 51           ~ 295 0
2 TMC-1 MoC 04 41 45.9 +25 41 27           ~ 1521 0
3 NAME Orion-KL SFR 05 35 14.16 -05 22 21.5           ~ 2153 1
4 NAME Orion Bright Bar reg 05 35 22.30 -05 24 33.0           ~ 797 0
5 NAME Horsehead Nebula DNe 05 40 59.0 -02 27 30           ~ 480 0
6 NAME Mon R2 IRS 4 * 06 07 45.25 -06 23 19.9           ~ 18 0
7 NAME Mon R2 IRS 5 * 06 07 45.6 -06 22 40           ~ 16 0
8 NAME Mon R2 IRS 2 * 06 07 45.83 -06 22 53.5           B0 106 0
9 NAME Mon R2 IRS 1 cor 06 07 46.20 -06 23 09.5           B0 62 0
10 NAME Mon R2 HII 06 07 47.58 -06 22 42.6           ~ 693 2
11 NAME Mon R2 IRS 3 Y*O 06 07 47.8 -06 22 55           ~ 139 0
12 QSO B0605-0834 BLL 06 07 59.6994046176 -08 34 49.980131256     18.5 17.70   ~ 420 1
13 IRAS 16293-2422 cor 16 32 22.56 -24 28 31.8           ~ 1158 1

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2022.05.25-19:35:56

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