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 (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:
FileName Lrecl Records Explanations
ReadMe 80 . This file table2.dat 115 102 Observations and Seyfert-type Classification table3.dat 131 102 Results from Spectral Fitting
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
Bytes Format Units Label Explanations
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
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.
Byte-by-byte Description of file: table3.dat
Bytes Format Units Label Explanations
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
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.
History: From electronic version of the journal
(End) Tiphaine Pouvreau [CDS] 08-Feb-2018
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