J/A+A/573/A93 Galaxies optical emission-line diagnostic diagrams (Vitale+, 2015)
Galaxy evolution across the optical emission-line diagnostic diagrams?
Vitale M., Fuhrmann L., Garcia-Marin M., Eckart A., Zuther J., Hopkins A.M.
<Astron. Astrophys., 573, A93-93 (2015)>
=2015A&A...573A..93V 2015A&A...573A..93V
ADC_Keywords: Galaxies, radio ; Morphology
Keywords: galaxies: evolution - radio continuum: galaxies -
methods: observational - techniques: spectroscopic -
galaxies: Seyfert - galaxies: star formation
Abstract:
The discovery of the M-σ relation, the local galaxy bimodality,
and the link between black-hole and host-galaxy properties have raised
the question of whether active galactic nuclei (AGN) play a role in
galaxy evolution. AGN feedback is one of the biggest observational
challenges of modern extragalactic astrophysics. Several theoretical
models implement AGN feedback to explain the observed galaxy
luminosity function and, possibly, the color and morphological
transformation of spiral galaxies into passive ellipticals. For
understanding the importance of AGN feedback, a study of the AGN
populations in the radio-optical domain is crucial. A mass sequence
linking star-forming galaxies and AGN has already been noted in
previous works, and it is now investigated as a possible evolutionary
sequence. We observed a sample of 119 intermediate-redshift
(0.04≤z<0.4) SDSS-FIRST radio emitters with the Effelsberg 100-m
telescope at 4.85 and 10.45GHz and obtained spectral indices. The
sample includes star-forming galaxies, composite galaxies (with mixed
contribution to line emission from star formation and AGN activity),
Seyferts, and low ionization narrow emission region (LINER) galaxies.
With these sources we search for possible evidence of spectral
evolution and a link between optical and radio emission in
intermediate-redshift galaxies. We find indications of spectral index
flattening in high-metallicity star-forming galaxies, composite
galaxies, and Seyferts. This "flattening sequence" along the
[NII]-based emission-line diagnostic diagram is consistent with the
hardening of galaxy ionizing field, thanks to nuclear activity. After
combining our data with FIRST measurements at 1.4GHz, we find that the
three-point radio spectra of Seyferts and LINERs show substantial
differences, which are attributable to small radio core components and
larger (arcsecond sized) jet/lobe components, respectively. A visual
inspection of FIRST images seems to confirm this hypothesis. Galaxies
along this sequence are hypothesized to be transitioning from the
active star-forming galaxies (blue cloud) to the passive elliptical
galaxies (red sequence). This supports the suggestion that AGN both
play a role in shutting down star formation and allow the transition
from one galaxy class to the other.
Description:
Observations at the Effelsberg 100-m telescope were performed between
February and October 2013 in a total of seven single observing
sessions. Each source was observed at 4.85GHz (6cm) and 10.45GHz
(2.8cm) with multi-feed heterodyne receivers mounted in the secondary
focus to derive radio spectral indices from (quasi-) simultaneous
observations (guaranteeing measurements free of source variability).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 96 119 Sources observed with the Effelsberg telescope
at 10.45 and 4.85GHz
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Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 5 F5.3 --- z [0/0.4] Redshift
7- 14 F8.4 deg RAdeg Right ascension (J2000)
16- 22 F7.4 deg DEdeg Declination (J2000)
24- 30 F7.2 mJy F1.4 Integrated flux density at 1.4GHz
32- 37 F6.4 Jy F10.45 Flux density at 10.45GHz
39- 44 F6.4 Jy e_F10.45 rms uncertainty on F10.45GHz
46- 51 F6.4 Jy F4.85 Flux density at 4.85GHz
53- 58 F6.4 Jy e_F4.85 rms uncertainty on F4.85GHz
60- 69 A10 --- MType Optical morphology from SDSS images (1)
71- 80 A10 --- RMorph Radio morphology from FIRST images (2)
82- 92 A11 --- Activity Activity type from NED (3)
95- 96 A2 --- NIId [LCS FS] Spectral classification according to
the [NII]-based diagnostic diagram (4)
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Note (1): Optical morphologies are:
E = elliptical
Cl = cluster
S = spiral
SB = barred spiral
PM = post merger
Comp = compact
int = interacting
Note (2): Radio morphologies are:
PS = point source
NAT = narrow angle tales
Extend = extended source
Asym dbl = asymmetric double
FRI = FR I radio source
FRII = FR II radio source
jet = presence of jet
lobe = presence of lobe
Note (3): Abbreviations used in the activity classification:
r-l = radio-loud
Blaz = blazars
cand. = candidate
Note (4): [NII]-based diagnostic diagram spectral classification as follows:
L = LINER
S = Seyfert
C = composite
SF = star-forming
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 27-Feb-2015