J/MNRAS/496/309 Behaviour of the MgII 2798Å line in AGNs (Homan+, 2020)
Behaviour of the MgII 2798Å line over the full range of AGN variability.
Homan D., MacLeod C.L., Lawrence A., Ross N.P., Bruce A.
<Mon. Not. R. Astron. Soc., 496, 309-327 (2020)>
=2020MNRAS.496..309H 2020MNRAS.496..309H (SIMBAD/NED BibCode)
ADC_Keywords: Active gal. nuclei ; Black holes ; QSOs ; Redshifts ;
Spectra, ultraviolet ; Optical
Keywords: galaxies: active - quasars: emission lines - quasars: general
Abstract:
We investigate the responsiveness of the 2798Å MgII broad emission
line in active galactic nuclei (AGNs) on time-scales of several years.
Our study is based on a sample of extremely variable AGNs as well as a
broad population sample. The observed response of the line in previous
studies has been mixed. By focusing on extreme variability
(|Δg|>1), we find that MgII clearly does respond to the
continuum. However, the degree of responsiveness varies strikingly
from one object to another: We see cases of MgII changing by as much
as the continuum, more than the continuum, or very little at all. In
74 per cent of the highly variable sample, the behaviour of MgII
corresponds with that of Hβ, with 30 per cent of the objects
showing large variations in both lines. We do not detect any change in
the line width that would correspond to broad-line region 'breathing',
in accordance with results from the literature. Some of the objects in
our highly variable sample show a clear asymmetry in the MgII profile.
This skewness can be both to the blue and the red of the line centre.
Results from our broad population sample show that highly variable
quasars have lower Eddington ratios. This result holds for the
variability of the continuum, but the correlation is significantly
reduced for the variability of the MgII line. For the first time, we
present an overview of the value of the intrinsic Baldwin effect for
MgII in a large sample.
Description:
All observations for SDSS were made using the 2.5m Sloan telescope at
Apache Point (Gunn et al. 2006AJ....131.2332G 2006AJ....131.2332G), as part of the
SDSS-I/II, SDSS-III/BOSS, and SDSS-IV/eBOSS observation campaigns.
The new observations were all part of the study discussed in MacLeod
et al. (2019ApJ...874....8M 2019ApJ...874....8M, Cat. J/ApJ/874/8). The observations were
made using the Intermediate Spectrograph and Imaging System on the
4.2m WHT in La Palma, with the Blue Channel Spectrograph on the MMT on
the 6.5m telescope (Mt. Hopkins, Arizona) and the Low Dispersion
Survey Spectrograph 3 (LDSS3)-C on the 6.5m Magellan telescope. All
observations were reduced using standard long-slit spectroscopy
methods. The flux calibration of the MMT and Magellan spectra has been
scaled to that of SDSS by matching the [OIII]4959 and [OIII]5007
fluxes. For the WHT spectra, we deemed the flux calibration of our
spectra to be of sufficient quality not to require this additional
grey scaling.
The supervariable sample is a combination of two data sets. The first
is the Changing Look Quasar (CLQ) sample presented in MacLeod et al.
(2016MNRAS.457..389M 2016MNRAS.457..389M) and the second is the CLQ candidate sample
presented in MacLeod et al. (2019ApJ...874....8M 2019ApJ...874....8M, Cat. J/ApJ/874/8).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table4.dat 107 43 Overview of the results of the spectral fitting
for the supervariable sample
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See also:
V/154 : Sloan Digital Sky Surveys (SDSS), Release 16 (DR16)
(Ahumada+, 2020)
J/ApJ/874/8 : Follow-up spectroscopy of SDSS changing-look QSOs
(Macleod+, 2019)
Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 18 A18 --- Name SDSS source designation (HHMMSS.ss+DDMMSS.s)
20 A1 --- MgII [01-] Indicates whether
|ΔfMgII|≥0.5 or the continuum is
stable (1)
22 I1 --- CLQ [0/1] Indicates whether the object was
identified as a CLQ in MacLeod et al.
(2019ApJ...874....8M 2019ApJ...874....8M, Cat. J/ApJ/874/8)
24- 27 I4 d maxDtsp Time span between the spectral epochs, in
the AGN rest frame
29- 34 F6.1 10+35W DL2798 Change in the continuum luminosity (2)
36- 40 F5.1 10+35W e_DL2798 Error on DL2798 (2)
42- 45 F4.1 10+35W DLMgII Change in the MgII line luminosity (2)
47- 50 F4.1 10+35W e_DLMgII Error on DLMgII (2)
52- 56 F5.2 --- Df2798 Fractional change in the continuum flux
level at the line centre (2)
58- 62 F5.2 --- DfMgII Fractional change in the MgII line flux (2)
64- 68 F5.1 0.1nm Dsigma Change in the MgII line width (2)
70- 73 F4.1 0.1nm e_Dsigma Error on Dsigma (2)
75- 79 F5.3 --- z Redshift
81- 84 F4.1 [10-7W] logLbol Logarithm of the bolometric luminosity (3)
86- 89 F4.1 [Msun] logMBH Logarithm of the black hole mass (3)
91- 94 F4.1 [-] logEddr Logarithm of the Eddington ratio (3)
96- 98 F3.1 mag maxDg Maximum absolute change in g-band photometry
over the period between spectral
observations (4)
100- 107 A8 --- Tel Telescope with which the latest spectral
observation was made
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Note (1): Flag as follows:
1 = |ΔfMgII|≥0.5
0 = |ΔfMgII|=<0.5
- = The continuum is stable
Note (2): For objects with more than two spectra available, the changes are
calculated between the two spectra with the largest |ΔL2798|
Note (3): Values from Shen et al. (2011ApJS..194...45S 2011ApJS..194...45S, Cat. J/ApJS/194/45)
Note (4): Value based on SDSS, PS1 (Heinis et al. 2016ApJ...826...62H 2016ApJ...826...62H), and
Catalina Real Time Survey (CRTS; Drake et al. 2009ApJ...696..870D 2009ApJ...696..870D,
Cat. J/ApJ/696/870) data
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History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 27-Jun-2023