J/A+A/654/A132 X-shooter spectra of AGN and inactive galaxies (Burtscher+, 2021)
LLAMA: Stellar populations in the nuclei of ultra-hard X-ray-selected AGN and
matched inactive galaxies.
Burtscher L., Davies R.I., Shimizu T.T., Riffel R., Rosario D.J.,
Hicks E.K.S., Lin M.-Y., Riffel R.A., Schartmann M., Schnorr-Mueller A.,
Storchi-Bergmann T., Orban de Xivry G., Veilleux S.
<Astron. Astrophys. 654, A132 (2021)>
=2021A&A...654A.132B 2021A&A...654A.132B (SIMBAD/NED BibCode)
ADC_Keywords: Active gal. nuclei ; Spectra, ultraviolet ; Spectra, optical ;
Spectra, infrared
Keywords: galaxies: active - galaxies: evolution - galaxies: nuclei -
galaxies: Seyfert - galaxies: stellar content -
techniques: spectroscopic
Abstract:
The relation between nuclear (≲50pc) star formation and nuclear
galactic activity is still elusive; theoretical models predict a
link between the two, but it is unclear whether active galactic nuclei
(AGNs) should appear at the same time, before, or after nuclear star
formation activity. We present a study of this relation in a complete,
volume-limited sample of nine of the most luminous
(logL14-195keV>1042.5erg/s) local AGNs (the LLAMA sample),
including a sample of 18 inactive control galaxies (six star-forming;
12 passive) that are matched by Hubble type, stellar mass
(9.5≲logM*/M☉≲10.5), inclination, and distance. This allows us
to calibrate our methods on the control sample and perform a
differential analysis between the AGN and control samples.
We performed stellar population synthesis on VLT/X-shooter spectra in
an aperture corresponding to a physical radius of ∼150pc. We find
young (≲30Myr) stellar populations in seven out of nine AGNs and in
four out of six star-forming control galaxies. In the non-star-forming
control population, in contrast, only two out of 12 galaxies show such
a population. We further show that these young populations are not
indicative of ongoing star formation, providing evidence for models
that see AGN activity as a consequence of nuclear star formation.
Based on the similar nuclear star formation histories of AGNs and
star-forming control galaxies, we speculate that the latter may turn
into the former for some fraction of their time. Under this
assumption, and making use of the volume completeness of our sample,
we infer that the AGN phase lasts for about 5% of the nuclear
starburst phase.
Description:
Spectra of all observations considered for this publication,
i.e. all 49 observations mentioned in Table 2 of the paper. Please see
Table 2 for the authors' judgement regarding the data quality of these
observations.
For any questions regarding the data or its quality, please contact
Dr. Leonard Burtscher, burtscher(at)strw.leidenuniv.nl, www.ileo.de or on
Twitter as (at)LeoBurtscher.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 59 49 All observations
sp/* . 49 Individual spectra
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1 A1 --- Type [AI] A for AGN, I for inactive galaxies
3- 11 A9 --- OB Name of ESO observing block
13- 22 A10 "date" Obs.dat Date of night began
24- 28 F5.2 arcsec Seeing ?=-1 Seeing
30- 35 F6.1 deg ParAngle Parallactic angle at the start of the
observation
37 I1 --- Flag [0/1]? Flag (1)
39- 59 A21 --- FileName Name fo the spectrum file in subdirectory sp
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Note (1): Flag as follows:
1 = this OB was used for the further analysis
0 = this OB was not used for the further analysis
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Byte-by-byte Description of file: sp/*
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Bytes Format Units Label Explanations
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2- 8 F7.2 0.1nm lambda Wavelength (Angstroem)
12- 19 F8.5 --- Fobs Observed spectrum, normalised (1)
23- 29 F7.5 --- Ffit Fitted spectrum (same normalisation as Fobs)
31- 38 F8.3 --- Weight Weight
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Note (1): see paper for description and normalisation factor in terms of
stellar mass: Table 3, last column.
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Acknowledgements:
Leonard Burtscher, burtscher(at)strw.leidenuniv.nl
(End) Patricia Vannier [CDS] 11-Aug-2021