2013ApJ...769...48N


Query : 2013ApJ...769...48N

2013ApJ...769...48N - Astrophys. J., 769, 48 (2013/May-3)

Herschel/HIFI observations of a new interstellar water maser: the 532-441 transition at 620.701 GHz.

NEUFELD D.A., WU Y., KRAUS A., MENTEN K.M., TOLLS V., MELNICK G.J. and NAGY Z.

Abstract (from CDS):

Using the Herschel Space Observatory's Heterodyne Instrument for the Far-Infrared, we have performed mapping observations of the 620.701 GHz 532-441 transition of ortho-H2 O within a ∼1.'5x1.'5 region encompassing the Kleinmann-Low nebula in Orion (Orion-KL), and pointed observations of that transition toward the Orion South condensation and the W49N region of high-mass star formation. Using the Effelsberg 100 m radio telescope, we obtained ancillary observations of the 22.23508 GHz 616-523 water maser transition; in the case of Orion-KL, the 621 GHz and 22 GHz observations were carried out within 10 days of each other. The 621 GHz water line emission shows clear evidence for strong maser amplification in all three sources, exhibiting narrow (∼1 km/s FWHM) emission features that are coincident (kinematically and/or spatially) with observed 22 GHz features. Moreover, in the case of W49N–for which observations were available at three epochs spanning a 2 yr period–the spectra exhibited variability. The observed 621 GHz/22 GHz line ratios are consistent with a maser pumping model in which the population inversions arise from the combined effects of collisional excitation and spontaneous radiative decay, and the inferred physical conditions can plausibly arise in gas heated by either dissociative or non-dissociative shocks. The collisional excitation model also predicts that the 22 GHz population inversion will be quenched at higher densities than that of the 621 GHz transition, providing a natural explanation for the observational fact that 22 GHz maser emission appears to be a necessary but insufficient condition for 621 GHz maser emission.

Abstract Copyright:

Journal keyword(s): ISM: molecules - masers - molecular processes - submillimeter: ISM

VizieR on-line data: <Available at CDS (J/ApJ/769/48): table3.dat>

Simbad objects: 15

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Number of rows : 15
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2023
#notes
1 IRC +10011 OH* 01 06 25.9879717848 +12 35 52.896392052   20.7   18.26 14.01 M8 413 0
2 3C 84 Sy2 03 19 48.1599902040 +41 30 42.108850836   13.10 12.48 11.09   ~ 3835 3
3 V* IK Tau Mi* 03 53 28.8924743304 +11 24 21.895183368 16.99 17.03 13.39 7.29 3.20 M7-11 613 0
4 NAME Orion S reg 05 35 12.9 -05 24 10           ~ 138 0
5 NAME OMC1 Ridge reg 05 35 13.4 -05 23 07           ~ 126 0
6 NAME Orion-KL SFR 05 35 14.16 -05 22 21.5           ~ 2190 1
7 NAME Ori Region reg 05 35 17.30 -05 23 28.0           ~ 544 0
8 NAME Orion Molecular Cloud MoC 05 56 -01.8           ~ 1018 1
9 V* VY CMa s*r 07 22 58.32877 -25 46 03.2355 12.01 10.19 7.95     M5Iae 1066 0
10 3C 286 Sy1 13 31 08.2883506368 +30 30 32.960091564   17.51 17.25     ~ 4146 2
11 V* W Hya Mi* 13 49 02.0018313132 -28 22 03.532006894   8.97 7.70     M7.5-9e 627 0
12 W 49n HII 19 10 13.2 +09 06 12           ~ 447 3
13 [DJW84] W49 G1 HII 19 10 13.42 +09 06 12.8           ~ 21 0
14 [DJW84] W49 G2 HII 19 10 13.47 +09 06 13.2           ~ 18 0
15 NGC 7027 PN 21 07 01.571952 +42 14 10.47120   10.358 8.831 10.157   ~ 2412 1

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2022.11.30-13:08:05

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