J/ApJ/806/74 NH3 line profiles in star-forming regions (Camarata+, 2015)
The NH3 hyperfine intensity anomaly in high-mass star-forming regions.
Camarata M.A., Jackson J.M., Chambers E.
<Astrophys. J., 806, 74 (2015)>
=2015ApJ...806...74C 2015ApJ...806...74C (SIMBAD/NED BibCode)
ADC_Keywords: H II regions ; Molecular clouds ; Radio lines ;
Line Profiles ; Interstellar medium
Keywords: ISM: clouds; ISM: molecules; stars: formation
Abstract:
Anomalous ammonia (NH3) spectra, exhibiting asymmetric hyperfine
satellite intensity profiles in the (J,K)=(1,1) inversion transition,
have been observed in star-forming regions for over 35 years. We
present a systematic study of this "hyperfine intensity anomaly" (HIA)
toward a sample of 334 high-mass star forming regions: 310 high-mass
(≳100M☉) clumps and 24 infrared dark clouds. The HIA is
ubiquitous in high-mass star forming regions. Although LTE excitation
predicts that the intensity ratios of the outer satellites and inner
satellites are exactly unity, for this sample the ensemble average
ratios are 0.812±0.004 and 1.125±0.005, respectively. We have
quantified the HIA and find no significant relationships between the
HIA and temperature, line width, optical depth, and the stage of
stellar evolution. The fact that HIAs are common in high-mass
star-forming regions suggests that the conditions that lead to HIAs
are ubiquitous in these regions. A possible link between HIAs and the
predictions of the competitive accretion model of high-mass star
formation is suggested; however, the expected trends of HIA strength
with clump evolutionary stage, rotational temperature, and line width
for evolving cores in competitive accretion models are not found.
Thus, the exact gas structures that produce HIAs remain unknown.
Turbulent gas structures are a possible explanation, but the details
need to be explored.
Description:
We obtained publicly released Effelsberg Telescope data from Wienen et
al. (2012, J/A+A/544/A146), who observed NH3 (1,1), (2,2), and (3,3)
lines toward 862 massive clumps (≳100M☉) detected by the APEX
Telescope Large Area Survey of the GALaxy (ATLASGAL). These
observations were carried out between 2008 and 2010 with the
Effelsberg 100m telescope.
Additionally, we observed the NH3 (1,1), (2,2), and (3,3) lines in 119
IRDCs. These observations were carried out at the 64m Parkes radio
telescope in New South Wales, Australia from 2008 June 19-20 and 2009
June 12-13.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 98 334 Source properties and hyperfine intensity anomaly
(HIA) results
--------------------------------------------------------------------------------
See also:
J/MNRAS/443/1555 : ATLASGAL massive star forming clumps (Urquhart+, 2014)
J/ApJ/777/157 : 90GHz obs. of high-mass star-forming regions (Hoq+, 2013)
J/A+A/544/A146 : ATLASGAL cold high-mass clumps with NH3 (Wienen+, 2012)
J/A+A/540/A113 : Starless clumps in ATLASGAL (Tackenberg+, 2012)
J/ApJ/715/310 : Early stages of star formation in IRDCs (Rathborne+, 2010)
J/ApJ/653/1325 : Galactic distribution of infrared dark clouds (Simon+, 2006)
J/ApJ/641/389 : Millimetric observations of IRDC cores (Rathborne+, 2006)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 14 A14 --- Name Source Name (GL.ll+B.bb)
16 A1 --- n_Name [*] Flag on Source Name (1)
18- 24 F7.3 deg GLON Galactic longitude
26- 31 F6.3 deg GLAT Galactic latitude
33- 39 F7.1 K Trot [11/25]?=-9999 NH3 Rotational Temperature (2)
41- 47 F7.1 K e_Trot [0.3/2]?=-9999 Uncertainty in Trot
49- 52 F4.2 --- HIAa [0.4/1.4] Ratio of NH3 outer satellite
intensities (3)
54- 57 F4.2 --- e_HIAa [0.02/0.2] Uncertainty in HIAa
59- 62 F4.2 --- HIAb [0.6/3.1] Ratio of NH3 inner satellite
intensities (4)
64- 67 F4.2 --- e_HIAb [0.02/0.4] Uncertainty in HIAb
69- 80 A12 --- Class Classification (HII, Protostellar, Quiescent
or Unclassified) (5)
82- 89 F8.2 --- tau [0.3/3.9]?=-9999 Optical Depth, τ (2)
91- 98 F8.2 --- e_tau [0.04/0.3]?=-9999 Uncertainty in tau
--------------------------------------------------------------------------------
Note (1): Denotes a source detected by CORNISH survey.
Note (2): Trot and tau calculated following Ho & Townes, 1983ARA&A..21..239H 1983ARA&A..21..239H
Note (3): Defined as NH3 (J,K)=(1,1) ratio of outer satellite
intensities ILO/IRO (F=1->0 "left-outer" (LO) vs
F=0->1 "right-outer" satellite intensities; see Figure 2).
Note (4): Defined as NH3 (J,K)=(1,1) ratio of inner satellite
intensities ILI/IRI (F=1->2 "left-inner" (LI) vs
F=2->1 "right-inner" (RO) satellite intensities; see Figure 2).
Note (5): Classification based on Chambers et al. (2009ApJS..181..360C 2009ApJS..181..360C)
using Spitzer IR data.
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 12-Oct-2015