J/ApJ/821/33 Broad Hβ emission line in 102 Seyfert galaxies (Runco+, 2016)
Broad Hβ emission-line variability in a sample of 102 local active
galaxies.
Runco J.N., Cosens M., Bennert V.N., Scott B., Komossa S., Malkan M.A.,
Lazarova M.S., Auger M.W., Treu T., Park D.
<Astrophys. J., 821, 33-33 (2016)>
=2016ApJ...821...33R 2016ApJ...821...33R (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, Seyfert ; Balmer lines ; Redshifts ; Spectroscopy ;
Galaxies, nearby
Keywords: accretion, accretion disks - galaxies: active - galaxies: evolution -
galaxies: Seyfert - galaxies: statistics
Abstract:
A sample of 102 local (0.02=<z=<0.1) Seyfert galaxies with black hole
masses MBH>107M☉ was selected from the Sloan Digital Sky Survey
(SDSS) and observed using the Keck 10 m telescope to study the scaling
relations between MBH and host galaxy properties. We study profile
changes of the broad Hβ emission line within the three to nine year
time frame between the two sets of spectra. The variability of the
broad Hβ emission line is of particular interest, not only because it
is used to estimate MBH, but also because its strength and width are
used to classify Seyfert galaxies into different types. At least some
form of broad-line variability (in either width or flux) is observed
in the majority (∼66%) of the objects, resulting in a Seyfert-type
change for ∼38% of the objects, likely driven by variable accretion
and/or obscuration. The broad Hβ line virtually disappears in 3/102
(∼3%) extreme cases. We discuss potential causes for these changing
look active galactic nuclei. While similar dramatic transitions have
previously been reported in the literature, either on a case-by-case
basis or in larger samples focusing on quasars at higher redshifts,
our study provides statistical information on the frequency of Hβ
line variability in a sample of low-redshift Seyfert galaxies.
Description:
A sample of 102 local (0.02=<z=<0.1) type-1 Seyfert galaxies was selected
from the SDSS data release six (DR6) (Adelman-McCarthy et al. 2008,
Cat. II/282).
SDSS spectra are obtained from a 2.5 m ground-based telescope with a 3"
diameter circular optical fiber and an exposure time of 54 s. SDSS spectra
cover a wavelength range of 3800-9200 Å with an instrumental resolution
of 170 km/s.
The 102 objects selected from SDSS were observed again between 2009
January and 2010 March with the Low Resolution Imaging Spectrometer (LRIS)
at the Keck 10 m telescope using a 1"x2" wide rectangular longslit aligned
with the major axis of the host galaxy (given by SDSS).
For eight objects with significantly weaker or apparently absent broad
Hβ emission in the Keck spectra, follow-up observations were conducted
in 2013 January and March with the 3 m Shane telescope of Lick observatory
using the Kast spectrograph and 60 minutes total exposure time per object.
The slit was aligned either along the major axis or perpendicular to it.
1D spectra were extracted using a 4 pixel (∼3") width centered on the peak
flux to mimic the 3" diameter circular fiber of SDSS.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 115 102 Observations and Seyfert-type Classification
table3.dat 131 102 Results from Spectral Fitting
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See also:
VII/173 : Catalogue of Seyfert Galaxies (Lipovetsky+, 1988)
II/282 : The SDSS Photometric Catalog, Release 6
(Adelman-McCarthy+, 2007)
II/294 : The SDSS Photometric Catalog, Release 7
(Adelman-McCarthy+, 2009)
V/147 : The SDSS Photometric Catalogue, Release 12 (Alam+, 2015)
J/ApJ/809/20 : The MBH-σ relation for active galaxies (Bennert+, 2015)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- ID Target identifier (HHMM+DDMM)
11- 12 I2 h RAh Hour of Right Ascension (J2000)
14- 15 I2 min RAm Minute of Right Ascension (J2000)
17- 21 F5.2 s RAs Second of Right Ascension (J2000)
23 A1 --- DE- Sign of the Declination (J2000)
24- 25 I2 deg DEd Degree of Declination (J2000)
27- 28 I2 arcmin DEm Arcminute of Declination (J2000)
30- 33 F4.1 arcsec DEs Arcsecond of Declination (J2000)
35- 39 F5.3 --- z Redshift from SDSS-DR7 (Cat. II/294)
41- 51 A11 "date" DateS Date on which SDSS spectrum was taken
53- 57 I5 d MJDS Modified Julian Date
59- 61 F3.1 --- STypeS [1/1.8] Seyfert-type classification based
on SDSS spectrum
63- 73 A11 "date" DateK Date on which Keck spectrum was taken
75- 79 I5 d MJDK Modified Julian Date
81- 83 F3.1 --- STypeK [1/1.9] Seyfert-type classification based
on Keck spectrum (1)
85- 88 I4 s ExpTime Exposure time of Keck observation (2)
90- 93 F4.2 yr DTime Time between SDSS and Keck observation
95-105 A11 "date" DateL ? Date on which Lick spectrum was taken
107-111 I5 d MJDL ? Modified Julian Date
113-115 F3.1 --- STypeL [1.8/2]? Seyfert-type classification based
on Lick spectrum
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Note (1): Note that because Keck spectra do not extend to Hα, we cannot
differentiate between type-1.9 and type-2, and conservatively classify
these objects in question as type-1.9.
Note (2): Note that the exposure time for all SDSS spectra is 54s.
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- ID Target identifier (HHMM+DDMM)
10 A1 --- n_ID [n] Note on ID (1)
12- 16 I5 km/s sigmaHbS ? Second moment of broad Hβ from SDSS
spectrum
18- 20 I3 km/s e_sigmaHbS ? Uncertainty in sigmaHbS
22- 26 I5 km/s FWHMS ? Full width at half maximum of broad Hβ
from SDSS spectrum
28- 31 I4 km/s e_FWHMS ? Uncertainty in FWHMS
33- 38 F6.4 --- FHb/OIIIS ? Integrated flux ratio of Hβ/[O III]
from SDSS spectrum
40- 45 F6.4 --- e_FHb/OIIIS ? Uncertainty in FHb/OIIIS
47- 52 F6.2 --- FHbS ? Integrated flux ratio of Hβ
broad/narrow from SDSS spectrum
54- 58 F5.2 --- e_FHbS ? Uncertainty in FHbS
60- 66 F7.4 --- FHbpeakS ? Peak flux ratio of Hβ broad/narrow
from SDSS spectrum
68- 73 F6.4 --- e_FHbpeakS ? Uncertainty in FHbpeakS
75 A1 --- FeIIS [YN] Whether Fe II was subtracted from
the SDSS spectrum during the fitting process
77- 80 I4 km/s sigmaHbK ? Second moment of broad Hβ from Keck
spectrum
82- 84 I3 km/s e_sigmaHbK ? Uncertainty in sigmaHbK
86- 89 I4 km/s FWHMK ? Full width at half maximum of broad Hβ
from Keck spectrum
91- 93 I3 km/s e_FWHMK ? Uncertainty in FWHMK
95- 99 F5.3 --- FHb/OIIIK ? Integrated flux ratio of Hβ/[O III]
from Keck spectrum
101-105 F5.3 --- e_FHb/OIIIK ? Uncertainty in FHb/OIIIK
107-111 F5.2 --- FHbK ? Integrated flux ratio of Hβ
broad/narrow from Keck spectrum
113-117 F5.2 --- e_FHbK ? Uncertainty in FHbK
118 A1 --- u_FHbK [)] Uncertainty flag on FHbK (2)
120-123 F4.2 --- FHbpeakK ? Peak flux ratio of Hβ broad/narrow
from Keck spectrum
125-128 F4.2 --- e_FHbpeakK ? Uncertainty in FHbpeakK
129 A1 --- u_FHbpeakK [)] Uncertainty flag on FHbpeakK (2)
131 A1 --- FeIIK [YN] Whether Fe II was subtracted from
the Keck spectrum during the fitting process
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Note (1): Note as follows:
n = For object 1655+2014 the S/N was too low in both SDSS and Keck spectra
to produce a reliable fit to the Hβ region. No values are given
for this object and it is not included in the quantitative analysis.
Note (2): Flag as follows:
) = Values estimated from upper limits on the broad Hβ flux for objects
classified as Sy 1.9 or Sy 2, that is without an obvious broad Hβ
component. No width (FWHM or sigma) of broad Hβ is given in those
cases.
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History:
From electronic version of the journal
(End) Tiphaine Pouvreau [CDS] 08-Feb-2018