J/A+A/595/A65 APEX spectra of Centaurus A (Salome+, 2016)
Atomic-to-molecular gas phase transition triggered by the radio jet in
Centaurus A.
Salome Q., Salome P., Combes F., Hamer S.
<Astron. Astrophys. 595, A65 (2016)>
=2016A&A...595A..65S 2016A&A...595A..65S (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, radio ; Radio lines
Keywords: methods: data analysis - galaxies: individual: Centaurus A -
galaxies: evolution - galaxies: interactions -
galaxies: star formation - radio lines: galaxies
Abstract:
NGC 5128 (Centaurus A) is one of the best example to study
AGN-feedback in the local Universe. At 13.5kpc from the galaxy,
optical filaments with recent star formation are lying along the
radio-jet direction. We used the Atacama Pathfinder EXperiment (APEX)
to map the CO(2-1) emission all along the filaments structure.
Molecular gas mass of 8.2x10^7M☉ was found over the
4.2kpc-structure which represents about 3% of the total gas mass of
the NGC 5128 cold gas content. Two dusty mostly molecular structures
are identified, following the optical filaments. The region
corresponds to the crossing of the radio jet with the northern HI
shell, coming from a past galaxy merger. One filament is located at
the border of the HI shell, while the other is entirely molecular, and
devoid of HI gas. The molecular mass is comparable to the HI mass in
the shell, suggesting a scenario where the atomic gas was shocked and
transformed in molecular clouds by the radio jet. Comparison with
combined FIR Herschel and UV GALEX estimation of star formation rates
in the same regions leads to depletion times of more than 10 Gyr. The
filaments are thus less efficient than discs in converting molecular
gas into stars. Kinetic energy injection triggered by shocks all along
the jet/gas interface is a possible process that appears to be
consistent with MUSE line ratio diagnostics derived in a smaller
region of the northern filaments. Whether the AGN is the sole origin
of this energy input and what is the dominant (mechanical vs
radiative) mode for this process is however still to be investigated.
Description:
APEX spectra of 31 positions along the northern filaments of Centaurus
A. The observation conditions and properties of the spectra are
summarised in tables A.1 and A.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
tablea.dat 107 31 Journal of observations with APEX (table A1)
and CO luminosities and molecular masses in the
regions observed with APEX (table A2)
apex_cena.fits 2880 16 Spectra as single FITS file
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Byte-by-byte Description of file: tablea.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- Pos Position identification number
4- 5 I2 h RAh Right ascension (J2000)
7- 8 I2 min RAm Right ascension (J2000)
10- 14 F5.2 s RAs Right ascension (J2000)
16 A1 --- DE- Declination sign (J2000)
17- 18 I2 deg DEd Declination (J2000)
20- 21 I2 arcmin DEm Declination (J2000)
23- 26 F4.1 arcsec DEs Declination (J2000)
28- 31 F4.1 min Tobs Time of observation
33- 36 F4.2 mK rms rms determined with both polarisations
and are given in main beam temperature
38- 40 A3 --- Run Observation run(s) (1)
42 A1 --- l_Tmb Limit flag on Tmb
43- 47 F5.2 mK Tmb Main-beam brightness temperature
49- 53 F5.1 km/s DeltaV Velocity relative to Cen A
55- 58 F4.1 km/s e_DeltaV ? rms uncertainty on DeltaV
60- 65 F6.1 km/s Vpeak ?=- Peak velocity
67- 69 F3.1 km/s e_Vpeak ? rms uncertainty on Vpeak
71 A1 --- l_ICO Limit flag on ICO
72- 76 F5.3 K.km/s ICO CO line intensity
78- 82 F5.3 K.km/s e_ICO ? rms uncertainty in ICO
84 A1 --- l_L'CO Limit flag on L'CO
85- 90 F6.3 10+5K.km/s/pc2 L'CO CO luminosity
92- 95 F4.2 10+5K.km/s/pc2 e_L'CO ? rms uncertainty on L'CO
97 A1 --- l_MH2 Limit flag on MH2
98-102 F5.2 10+6Msun MH2 Hydrogen molecular mass (2)
104-107 F4.2 10+6Msun e_MH2 ? rms uncertainty on MH2
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Note (1): The first run was made in September 2015, the second run extends from
the end of October to December.
Note (2): MH2 is the molecular mass derived from the CO(2-1) emission with a
standard conversion factor and an assumed CO(2-1)/CO(1-0) ratio of 0.55
(Charmandaris et al., 2000A&A...356L...1C 2000A&A...356L...1C).
For non-detections, an upper limit at 3σ been derived assuming a
linewidth of 30km/s.
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Acknowledgements:
Quentin Salome, quentin.salome(at)obspm.fr
(End) Patricia Vannier [CDS] 05-Oct-2016