2013ApJ...763...83M


Query : 2013ApJ...763...83M

2013ApJ...763...83M - Astrophys. J., 763, 83 (2013/February-1)

Herschel/PACS spectroscopic survey of protostars in Orion: the origin of far-infrared CO emission.

MANOJ P., WATSON D.M., NEUFELD D.A., MEGEATH S.T., VAVREK R., YU V., VISSER R., BERGIN E.A., FISCHER W.J., TOBIN J.J., STUTZ A.M., ALI B., WILSON T.L., DI FRANCESCO J., OSORIO M., MARET S. and POTEET C.A.

Abstract (from CDS):

We present far-infrared (57-196 µm) spectra of 21 protostars in the Orion molecular clouds. These were obtained with the Photodetector Array Camera and Spectrometer (PACS) on board the Herschel Space observatory as part of the Herschel Orion Protostar Survey program. We analyzed the emission lines from rotational transitions of CO, involving rotational quantum numbers in the range Jup= 14-46, using PACS spectra extracted within a projected distance of ≲ 2000 AU centered on the protostar. The total luminosity of the CO lines observed with PACS (LCO) is found to increase with increasing protostellar luminosity (Lbol). However, no significant correlation is found between LCO and evolutionary indicators or envelope properties of the protostars such as bolometric temperature, Tbol, or envelope density. The CO rotational (excitation) temperature implied by the line ratios increases with increasing rotational quantum number J, and at least 3-4 rotational temperature components are required to fit the observed rotational diagram in the PACS wavelength range. The rotational temperature components are remarkably invariant between protostars and show no dependence on Lbol, Tbol, or envelope density, implying that if the emitting gas is in local thermodynamic equilibrium, the CO emission must arise in multiple temperature components that remain independent of Lbol over two orders of magnitudes. The observed CO emission can also be modeled as arising from a single-temperature gas component or from a medium with a power-law temperature distribution; both of these require sub-thermally excited molecular gas at low densities (n(H2) ≲ 106/cm3) and high temperatures (T ≳ 2000 K). Our results suggest that the contribution from photodissociation regions, produced along the envelope cavity walls from UV-heating, is unlikely to be the dominant component of the CO emission observed with PACS. Instead, the "universality" of the rotational temperatures and the observed correlation between LCO and L bol can most easily be explained if the observed CO emission originates in shock-heated, hot (T ≳ 2000 K), sub-thermally excited (n(H2) ≲ 106/cm3) molecular gas. Post-shock gas at these densities is more likely to be found within the outflow cavities along the molecular outflow or along the cavity walls at radii ≳ several 100-1000 AU.

Abstract Copyright:

Journal keyword(s): circumstellar matter - ISM: jets and outflows - molecular processes - stars: formation - techniques: spectroscopic

Simbad objects: 28

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Number of rows : 28
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 [JCC87] IRAS 4B Y*O 03 29 12.058 +31 13 02.05           ~ 570 0
2 2MASS J05343542-0539589 Y*O 05 34 35.423 -05 39 58.96           ~ 9 0
3 HOPS 30 Y*O 05 34 44.0625 -05 41 25.638           ~ 8 0
4 HOPS 10 Y*O 05 35 09.0143 -05 58 27.526           ~ 11 0
5 HOPS 11 Y*O 05 35 13.4326 -05 57 58.154           ~ 11 0
6 NAME Orion-KL SFR 05 35 14.16 -05 22 21.5           ~ 2092 1
7 HOPS 91 Y*O 05 35 18.98 -05 00 51.6           ~ 34 0
8 HOPS 56 Y*O 05 35 19.4586 -05 15 32.779           ~ 14 0
9 HOPS 88 Y*O 05 35 22.4451 -05 01 14.123           ~ 49 1
10 ISOY J053523.33-051203.4 Y*O 05 35 23.417 -05 12 02.34           ~ 30 0
11 HOPS 87 Y*O 05 35 23.500 -05 01 29.58           ~ 19 0
12 HOPS 68 Y*O 05 35 24.2999 -05 08 30.686           ~ 52 0
13 2MASS J05352477-0510296 Y*O 05 35 24.777 -05 10 29.61           ~ 46 1
14 NAME OMC-2 IRS 3 HII 05 35 26.00 -05 10 16.6           ~ 63 0
15 IRAS 05329-0505 Y*O 05 35 26.746 -05 03 55.08           ~ 75 0
16 OMC 2 MoC 05 35 27 -05 10.1           ~ 409 1
17 HOPS 108 Y*O 05 35 27.07 -05 10 00.4           ~ 14 0
18 2MASS J05352762-0509337 Y*O 05 35 27.622 -05 09 33.78           ~ 77 0
19 TKK 870 Y*O 05 35 28.19 -05 03 41.2           ~ 39 0
20 HOPS 182 Y*O 05 36 18.83 -06 22 10.2           ~ 11 0
21 GBS-VLA J053622.86-064606.6 Y*O 05 36 22.84 -06 46 06.2           ~ 99 0
22 NAME Ori A MoC 05 38 -07.1           ~ 2774 0
23 HOPS 288 Y*O 05 39 55.95 -07 30 28.0           ~ 18 0
24 NAME Ori B MoC 05 41 43.0 -01 54 44           ~ 1226 0
25 IRAS 05399-0121 Y*O 05 42 27.68 -01 20 01.0           ~ 36 0
26 2MASS J05470160+0017594 Y*O 05 47 01.605 +00 17 59.43           ~ 5 0
27 2MASS J05475906+0035324 Y*O 05 47 59.067 +00 35 32.43           ~ 6 0
28 NAME ORI MOL CLOUD MoC 05 56 -01.8           ~ 916 1

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2021.08.04-14:26:44

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