2007A&A...466..977S


C.D.S. - SIMBAD4 rel 1.7 - 2020.11.29CET07:12:24

2007A&A...466..977S - Astronomy and Astrophysics, volume 466, 977-988 (2007/5-2)

Tracing high energy radiation with molecular lines near deeply embedded protostars.

STAEUBER P., BENZ A.O., JORGENSEN J.K., VAN DISHOECK E.F., DOTY S.D. and VAN DER TAK F.F.S.

Abstract (from CDS):

The aim is to probe high energy radiation emitted by deeply embedded protostars.Submillimeter lines of CN, NO, CO+ and SO+, and upper limits on SH+ and N2O are observed with the James Clerk Maxwell Telescope in two high-mass and up to nine low-mass young stellar objects and compared with chemical models.Constant fractional abundances derived from radiative transfer modeling of the line strengths are x(CN) ≃ a fewx10–11-10–8, x(NO) ≃10–9-10–8 and x(CO+) ≃10–12-10–10. SO+ has abundances of a fewx10–11 in the high-mass objects and upper limits of ≃10–12-10–11 in the low-mass sources. All abundances are up to 1-2 orders of magnitude higher if the molecular emission is assumed to originate mainly from the inner region (≲1000AU) of the envelope. For high-mass sources, the CN, SO+ and CO+ abundances and abundance ratios are best explained by an enhanced far-ultraviolet (FUV) field impacting gas at temperatures of a few hundred K. The observed column densities require that this region of enhanced FUV has scales comparable to the observing beam, such as in a geometry in which the enhanced FUV irradiates outflow walls. For low-mass sources, the required temperatures within the FUV models of T>300K are much higher than found in models, so that an X-ray enhanced region close to the protostar (r ≲500AU) is more plausible. Gas-phase chemical models produce more NO than observed, suggesting an additional reduction mechanism not included in current models.The observed CN, CO+ and SO+ abundances can be explained with either enhanced X-rays or FUV fields from the central source. High-mass sources likely have low opacity regions that allow the FUV photons to reach large distances from the central source. X-rays are suggested to be more effective than FUV fields in the low-mass sources. The observed abundances imply X-ray fluxes for the Class 0 objects of LX≃1029-1031erg/s, comparable to those observed from low-mass Class I protostars. Spatially resolved data are needed to clearly distinguish the effects of FUV and X-rays for individual species.

Abstract Copyright:

Journal keyword(s): stars: formation - stars: low-mass, brown dwarfs - ISM: molecules - X-rays: ISM

Simbad objects: 18

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Number of rows : 18

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2021
#notes
1 NAME W3 IRS 5 Y*O 02 25 40.54 +62 05 51.4           B1 330 0
2 [SDA2014] West4 Y*O 03 25 38.83 +30 44 06.2           ~ 242 1
3 IRAS F03226+3033 Y*O 03 25 38.83 +30 44 06.2           ~ 304 0
4 IRAS 03258+3104 Y*O 03 28 55.30 +31 14 27.8           ~ 160 1
5 [JCC87] IRAS 2A Y*O 03 28 55.55 +31 14 36.7           ~ 405 3
6 [JCC87] IRAS 4A Y*O 03 29 10.49 +31 13 30.8           ~ 611 1
7 [JCC87] IRAS 4 FIR 03 29 10.9 +31 13 26           ~ 468 0
8 NGC 1333 OpC 03 29 11 +31 18.6           ~ 1235 1
9 [JCC87] IRAS 4B Y*O 03 29 12.058 +31 13 02.05           ~ 562 0
10 LDN 1489 DNe 04 04 47.5 +26 19 42           ~ 198 0
11 IC 443 SNR 06 18 02.7 +22 39 36           ~ 1112 1
12 IRAS 16293-2422 cor 16 32 22.56 -24 28 31.8           ~ 1062 1
13 NAME Sgr B2 MoC 17 47 20.4 -28 23 07           ~ 1955 1
14 LDN 483 DNe 18 17 35 -04 39.8           ~ 216 0
15 NAME Serpens SMM 4 cor 18 29 57.1 +01 13 15           ~ 123 0
16 LDN 723 DNe 19 18 12 +19 13.6           ~ 153 0
17 RAFGL 2591 Y*O 20 29 25.03656 +40 11 20.3316           ~ 571 0
18 EM* LkHA 190 Or* 20 58 53.7336698326 +44 15 28.384667940   14.26 12.33 12.13   F7/G3I/IIe 479 0

    Equat.    Gal    SGal    Ecl

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2020.11.29-07:12:24

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