2016A&A...593A..46F


C.D.S. - SIMBAD4 rel 1.7 - 2019.11.12CET11:00:11

2016A&A...593A..46F - Astronomy and Astrophysics, volume 593A, 46-46 (2016/9-1)

Inferring the evolutionary stages of the internal structures of NGC 7538 S and IRS1 from chemistry.

FENG S., BEUTHER H., SEMENOV D., HENNING T., LINZ H., MILLS E.A.C. and TEAGUE R.

Abstract (from CDS):

Context. Radiative feedback of young (proto)stars and gas dynamics including gravitational collapse and outflows are important in high-mass star-forming regions (HMSFRs), for the reason that they may leave footprints on the gas density and temperature distributions, the velocity profile, and the chemical abundances.
Aims. We unambiguously diagnose the detailed physical mechanisms and the evolutionary status of HMSFRs.
Methods. We performed 0.4'' (∼1000AU) resolution observations at 1.37mm towards two HMSFRs, NGC 7538 S and IRS1, using the Plateau de Bure Interferometre (PdBI). The observations covered abundant molecular lines, including tracers of gas column density, hot molecular cores, shocks, and complex organic molecules. We present a joint analysis of the 1.37mm continuum emission and the line intensity of 15 molecular species (including 22 isotopologues). Assuming local thermal equilibrium (LTE), we derived molecular column densities and molecular abundances for each internal gas substructure that is spatially resolved. These derived quantities are compared with a suite of 1D gas-grain models.
Results. NGC 7538 S is resolved into at least three dense gas condensations. Despite the comparable continuum intensity of these condensations, their differing molecular line emission is suggestive of an overall chemical evolutionary trend from the northeast to the southwest. Line emission from MM1 is consistent with a chemically evolved hot molecular core (HMC), whereas MM3 remains a prestellar candidate that only exhibits emission of lower-excitation lines. The condensation MM2, located between MM1 and MM3, shows an intermediate chemical evolutionary status. Since these three condensations are embedded within the same parent gas core, their differing chemical properties are most likely due to the different warm-up histories, rather than the different dynamic timescales. Despite remaining spatially unresolved, in IRS1 we detect abundant complex organic molecules (e.g. NH2CHO, CH3OH, HCOOCH3, CH3OCH3), indicating that IRS1 is the most chemically evolved HMC presented here. We observe a continuum that is dominated by absorption features with at least three strong emission lines, potentially from CH3OH. The CH3OH lines which are purely in emission have higher excitation than the ones being purely in absorption. Potential reasons for this difference are discussed.
Conclusions. This is the first comprehensive comparison of observations of the two high-mass cores NGC 7538 S and IRS1 and a chemical model. We have found that different chemical evolutionary stages can coexist in the same natal gas core. Our achievement illustrates the strength of chemical analysis for understanding HMSFRs.

Abstract Copyright: © ESO, 2016

Journal keyword(s): stars: formation - stars: early-type - stars: individual: NGC 7538 IRS1 - stars: individual: NGC 7538 S - ISM: molecules - ISM: lines and bands

Simbad objects: 17

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Number of rows : 17

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
#notes
1 QSO B0016+73 QSO 00 19 45.78641940 +73 27 30.0174396     19.0 18.26   ~ 268 1
2 ICRF J005952.2+581223 QSO 00 59 52.2083579204 +58 12 23.682108462           ~ 15 1
3 NAME Per Arm PoG 03 30 +45.0           ~ 1194 0
4 NAME Orion-KL SFR 05 35 14.16 -05 22 21.5           ~ 1944 1
5 3C 273 BLL 12 29 06.6996828061 +02 03 08.598846466   13.05 14.830 14.11   ~ 5244 1
6 3C 345 QSO 16 42 58.8100340220 +39 48 36.999540578   16.81 16.59 16.84   ~ 1530 2
7 [CCE98b] 011.11-0.12 Cld 18 10.5 -19 23           ~ 83 1
8 RAFGL 2591 Y*O 20 29 25.2650 +40 11 26.532   18       ~ 562 5
9 EM* MWC 349 Em* 20 32 45.6328 +40 39 36.143   15.88 13.15 12.13   Bep 689 1
10 4C 60.32 Rad 21 48 16.04229735 +61 07 05.7944158           ~ 18 1
11 NGC 7538 OpC 23 13 37 +61 30.0           ~ 814 0
12 [WZS2012] NGC 7538 SC mm 23 13 44.510 +61 26 47.80           ~ 4 0
13 [WZS2012] NGC 7538 SB mm 23 13 44.750 +61 26 48.80           ~ 4 0
14 NGC 7538S Y*O 23 13 44.8 +61 26 51           ~ 72 1
15 [WZS2012] NGC 7538 SA1 mm 23 13 44.986 +61 26 49.80           ~ 4 0
16 [WBN74] NGC 7538 IRS 1 Y*O 23 13 45.318 +61 28 11.69           ~ 359 3
17 [WBN74] NGC 7538 IRS 9 Y*O 23 14 01.63 +61 27 20.2           ~ 336 0

    Equat.    Gal    SGal    Ecl

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2019.11.12-11:00:11

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