J/A+A/642/A166 Large scale mechanical heating in NGC4945 (Bellocchi+, 2020)
The multi-phase ISM in the nearby composite AGN-SB galaxy NGC 4945:
large-scale (parsecs) mechanical heating.
Bellocchi E., Martin-Pintado J., Gusten R., Requena-Torres M. A., Harris A.,
van der Werf P., Israel F., Weiss A., Kramer C., Garcia-Burillo S.,
Stutzki J.
<Astron. Astrophys. 642, A166 (2020)>
=2020A&A...642A.166B 2020A&A...642A.166B (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, nearby ; Galaxies, spectra ; Photometry
Keywords: ISM: molecules - infrared: galaxies - galaxies: ISM -
galaxies: starburst - galaxies: active -
galaxies: kinematics and dynamic
Abstract:
Understanding the dominant heating mechanism in the nuclei of galaxies
is crucial to understand star formation in starbursts (SB), active
galactic nuclei (AGN) phenomena and the relationship between the star
formation and AGN activity in galaxies. The analysis of the carbon
monoxide (12CO) rotational ladder versus the infrared continuum
emission (hereafter, 12CO/IR) in galaxies with different type of
activity have shown important differences between them.
We aim at carrying out a comprehensive study of the nearby composite
AGN-SB galaxy, NGC 4945, using spectroscopic and photometric data from
the Herschel satellite. In particular, we want to characterize the
thermal structure in this galaxy by a multi-transitions analysis of
the spatial distribution of the 12CO emission at different spatial
scales. We also want to establish the dominant heating mechanism at
work in the inner region of this object at smaller spatial scales
(≲200pc).
We present far-infrared (FIR) and sub-millimeter (sub-mm) 12CO line
maps and single spectra (from Jup=3 to 20) using the Heterodyne
Instrument for the Far Infrared (HIFI), the Photoconductor Array
Camera and Spectrometer (PACS), and the Spectral and Photometric
Imaging REceiver (SPIRE) onboard Herschel, and the Atacama Pathfinder
EXperiment (APEX). We combined the 12CO/IR flux ratios and the local
thermodynamic equilibrium (LTE) analysis of the 12CO images to
derive the thermal structure of the Interstellar Medium (ISM) for
spatial scales raging from ≲200pc to 2kpc. In addition, we also
present single spectra of low (12CO, 13CO and [CI]) and high
density (HCN, HNC, HCO+, CS and CH) molecular gas tracers obtained
with APEX and HIFI applying LTE and non-LTE analyses. Furthermore, the
Spectral Energy Distribution (SED) of the continuum emission from the
far-IR to sub-mm wavelengths is also presented.
From the non-LTE analysis of the low and high density tracers we
derive in NGC 4945 gas volume densities (103-106cm-3) similar to
those found in other galaxies with different type of activity. From
the 12CO analysis we found clear trend in the distribution of the
derived temperatures and the 12CO/IR ratios. It is remarkable that
at intermediate scales (360pc-1kpc, or 19"-57") we see large
temperatures in the direction of the X-ray outflow while at smaller
scales (≲200pc-360pc, or 9"-19"), the highest temperature, derived
from the high-J lines, is not found toward the nucleus, but toward the
galaxy plane. The thermal structure derived from the 12CO
multi-transition analysis suggests that mechanical heating, like
shocks or turbulence, dominates the heating of the ISM in the nucleus
of NGC4945 located beyond 100 pc (&500) from the center of the galaxy.
This result is further supported by the Kazandjian et al. (2015, Cat.
J/AJ/133/504) models, which are able to reproduce the emission
observed at high-J (PACS) 12CO transitions when mechanical heating
mechanisms are included. Shocks and/or turbulence are likely produced
by the barred potential and the outflow, observed in X-rays.
Description:
Photometric and spectroscopic data of the galaxy NGC 4945. In
particular, photometric data for PACS and SPIRE wavelengths and
spectroscopic data for HIFI+APEX, PACS, SPIRE instruments are given.
The data are stored in two main directories: fits and sp.
In fits directory are included the PACS and SPIRE maps shown in
Fig. 3., and the SPIRE SLW and SSW data cubes.
In sp, are included HIFI+APEX, PACS and SPIRE spectra.
HIFI_APEX spectra of the different molecules, as shown in Fig. 5,
named:
For 12CO, NGC4945[0123]CO.cold.txt or NGC4945[0123]CO.hot.txt
For 13CO, NGC494513CO[012].txt
For CH, NGC4945CH[012].txt
For CS, NGC4945CS[01234].txt
For HCN, NGC4945HCN[0123].txt
For HCO+, NGC4945HCO+[012].txt
For HNC, NGC4945HNC[0123].txt
For [CI], NGC4945CI[01].txt
PACS spectra shown in Fig. 12R, named NGC4945fitNN_[0123].txt,
where NN is the spx number (2, 3, 4, 5, 6, 7, 11 or 12).
Objects:
--------------------------------------------------
RA (2000) DE Designation(s)
--------------------------------------------------
13 05 27.28 -49 28 04.4 NGC4945 = ESO 219-24
--------------------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
listsp.dat 71 64 List of spectra
sp/* . 64 Individual spectra
listfits.dat 199 8 List of fits files
fits/* . 8 Individual fits files
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See also:
J/AJ/133/504 : Galaxies around CenA/M83 galaxy complex (Karachentsev+, 2007)
Herschel archive : http://archives.esac.esa.int/hsa/whsa
Byte-by-byte Description of file: listsp.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 45 A45 --- Title Title of the spectrum
51- 71 A21 --- FileName Name of the spectrum file in subdirectory sp
--------------------------------------------------------------------------------
Byte-by-byte Description of file: sp/*
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 22 F22.17 km/s Vel Velocity
24- 38 E15.9 K TmbObs ? Observed main beam temperature
40- 61 E22.9 K YmbMod ?=- Modelled main beam temperature
--------------------------------------------------------------------------------
Byte-by-byte Description of file: listfits.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 F9.5 deg RAdeg Right Ascension of center (J2000)
10- 18 F9.5 deg DEdeg Declination of center (J2000)
20- 23 I4 --- Nx Number of pixels along X-axis
25- 28 I4 --- Ny Number of pixels along Y-axis
30- 33 I4 --- Nz ? Number of slices for the datacubes
35- 60 A26 "datime" Obs.date Observation date
62- 72 E11.6 Hz bFREQ-LSR ? Lower value of FREQ-LSR for the datacubes
74- 84 E11.6 Hz BFREQ-LSR ? Upper value of FREQ-LSR for the datacubes
86- 96 E11.6 Hz dFREQ-LSR ? FREQ-LSR resolution
98-101 I4 Kibyte size Size of FITS file
103-146 A44 --- FileName Name of FITS file, in subdirectory fits
148-199 A52 --- Title Title of the FITS file
--------------------------------------------------------------------------------
Acknowledgements:
Enrica Bellocchi, enrica.bellocchi(at)gmail.com
CAB, CSIC-INTA, ESAC campus, Madrid
References:
Herschel archive: http://archives.esac.esa.int/hsa/whsa
(End) Enrica Bellocchi [CAB, Madrid], Patricia Vannier [CDS] 03-Aug-2020