J/A+A/627/A6 APEX spectra of Centaurus A (Salome+, 2019)
Physical conditions in Centaurus A's northern filaments.
I: APEX mid-J CO observations of CO-bright regions.
Salome Q., Salome P., Gusdorf A., Combes F.
<Astron. Astrophys. 627, A6 (2019)>
=2019A&A...627A...6S 2019A&A...627A...6S (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, radio; Radio lines
Keywords: methods: data analysis - galaxies: individual: Centaurus A -
galaxies: evolution - galaxies: ISM - galaxies: star formation -
radio lines: galaxies
Abstract:
NGC 5128 (Centaurus A) is one of the best targets to study
AGN-feedback in the local Universe. Optical filaments located at 16
kpc from the galaxy along the radio jet direction show recent star
formation, likely triggered by the interaction of the jet with an HI
shell. A large reservoir of molecular gas has been discovered outside
the HI. In this reservoir, lies the Horseshoe complex: a filamentary
structure seen in CO with ALMA and in Halpha with MUSE. The ionised
gas is mostly excited by shocks, with only a minor contribution of
star formation. We used the Atacama Pathfinder EXperiment (APEX) to
observe the 12CO(3-2) and 12CO(4-3) transitions, as well as dense gas
tracers in the Horseshoe complex. 12CO(3-2) and 12CO(4-3) are detected
for the first time in the northern filaments of Centaurus A, with
integrated intensity line ratios R32∼0.2 and R43∼0.1, compared to the
12CO(1-0) emission. We also derived a line ratio R21∼0.6, based on the
previous 12CO(2-1) observations of Salome et al. (2016, Cat.
J/A+A/595/A65). We used the non-LTE radiative transfer code RADEX and
determined that the molecular gas in this region has a temperature of
55-70K and densities between 2-6x102cm-3. Such densities are also
in agreement with results from the Paris-Durham shock code that
predicts a post-shock density of a few 100cm-3. However, we need
more observations of emission lines at a better angular resolution in
order to place tighter constraints on our radiative models, whether
they are used as a stand-alone tool (LVG codes) or combined with a
shock model.
Description:
APEX spectra of the 12CO(2-1), 12CO(3-2) and 12CO(4-3) emission,
as well as the HCN/HCO+(3-2) and [CI] lines, in one position of the
Horseshoe complex of Centaurus A. The observation conditions and
properties of the spectra are summarised in table 1 of the paper.
Objects:
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RA (2000) DE Designation(s)
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13 25 27.62 -43 01 08.8 Cen A = NGC 5128
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 133 6 List of fits spectra
fits/* . 6 Individual spectra
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See also:
J/A+A/595/A65 : APEX spectra of Centaurus A (Salome+, 2016)
Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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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- 47 A23 "datime" Obs.date Observation date
49- 60 E12.6 Hz bFreq Lower value of relative frequency
62- 72 E11.6 Hz BFreq Upper value of relative frequency
74- 84 E11.6 Hz dFreq Frequency resolution
86- 87 I2 Kibyte size Size of FITS file
89-103 A15 --- FileName Name of FITS file, in subdirectory fits
105-133 A29 --- Title Title of the FITS file
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Acknowledgements:
Quentin Salome, q.salome(at)irya.unam.mx
(End) Quentin Salome [IRyA-UNAM, Mexico], Patricia Vannier [CDS] 29-May-2019