J/A+A/643/A174 PKS J1209-2032 & CGRaBS J1549+5038 radio spectra (Mhaskey+, 2020)
uGMRT HI 21-cm absorption observations of two extremely inverted spectrum
sources.
Mhaskey M., Paul S., Gupta N., Mukherjee D., Gopal-Krishna
<Astron. Astrophys. 643, A174 (2020)>
=2020A&A...643A.174M 2020A&A...643A.174M (SIMBAD/NED BibCode)
ADC_Keywords: Active gal. nuclei ; QSOs ; Spectra, radio
Keywords: radiation mechanisms: non-thermal - galaxies: active - galaxies: ISM -
radio lines: ISM
Abstract:
We report the detection of HI 21-cm absorption in a member of the rare
and recently discovered class of compact radio sources, "Extremely
Inverted Spectrum Extragalactic Radio Sources (EISERS)" . EISERS
conceivably form a special sub-class of the inverted spectrum radio
galaxies since the spectral index of the optically thick part of the
spectrum for these sources crosses the synchrotron self absorption
limit of α=+2.5 (S(ν) ∝ να). We have
searched for HI absorption in two EISERS using the recently upgraded
Giant Metrewave Radio Telescope (uGMRT) and detected an absorption
feature in one of them. The strong associated HI absorption detected
against the source J1209-2032 (z=0.4040) implies an optical depth of
0.178±0.02 corresponding to an HI column density of
34.8±2.9x1020cm-2, for an assumed HI spin temperature of 100K
and covering factor of 1. This is among the highest known optical
depth and HI column densities found for compact radio sources of
peaked spectrum type and supports the free-free absorption model for
the steeply inverted radio spectrum of this source. For the other
source, J1549+5038 (z=2.171), no HI absorption was detected in our
observations.
Description:
Sources were observed on 05 November 2019 using Band-5 (J1209-2032)
and Band-3 (J1549+5038) of uGMRT. For both the observations, a
bandwidth of 12.5MHz split into 4096 frequency channels was used. For
J1209-2039, the observing band was centered at 1011.7MHz, and for
J1549+5038 at 447.5MHz.
uGMRT HI absorption line reduced spectra for J1209-2032 and J1549+5038
in tabular ASCII format are presented.
Objects:
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RA (2000) DE Designation(s)
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12 09 14.61 -20 32 39.0 J1209-2032 = PKS J1209-2032
15 49 17.47 +50 38 05.8 J1549+5038 = CGRaBS J1549+5038
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
j1209_sp.dat 30 820 J1209-2032 reduced spectra data
j1549_sp.dat 30 227 J1549+5038 reduced spectra data
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Byte-by-byte Description of file: j1209_sp.dat j1549_sp.dat
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Bytes Format Units Label Explanations
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1- 16 F16.10 km/s HV Heliocentric velocity
19- 30 F12.10 --- NFlux Normalised flux
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Acknowledgements:
Mukul Mhaskey, mukul(at)tls-tautenburg.de
(End) Patricia Vannier [CDS] 30-Sep-2020