J/MNRAS/383/581 Broad-line Balmer decrements in blue AGN (Dong+, 2008)
Broad-line Balmer decrements in blue active galactic nuclei.
Dong X., Wang T., Wang J., Yuan W., Zhou H., Dai H., Zhang K.
<Mon. Not. R. Astron. Soc., 383, 581-592 (2008)>
=2008MNRAS.383..581D 2008MNRAS.383..581D
ADC_Keywords: QSOs ; Active gal. nuclei ; Redshifts ; Spectroscopy ; Ultraviolet
Keywords: quasars: emission lines - quasars: general
Abstract:
We have investigated the broad-line Balmer decrements (H{alpha/Hβ)
for a large, homogeneous sample of Seyfert 1 galaxies and quasi-stellar
objects (QSOs) using spectroscopic data obtained in the Sloan Digital
Sky Survey. The sample, drawn from the Fourth Data Release, comprises
446 low-redshift (z≤0.35) active galactic nuclei (AGN) that have
blue optical continua as indicated by the spectral slopes in order
to minimize the effect of dust extinction. We find that (i) the
distribution of the intrinsic broad-line Hα/Hβ ratio can be
well described by log-Gaussian, with a peak at Hα/Hβ=3.06
and a standard deviation of about 0.03dex only; (ii) the Balmer
decrement does not correlate with AGN properties such as luminosity,
accretion rate and continuum slope, etc.; (iii) on average, the Balmer
decrements are found to be only slightly larger in radio-loud sources
(3.37) and sources having double-peaked emission-line profiles (3.27)
compared to the rest of the sample. We therefore suggest that the
broad-line Hα/Hβ ratio can be used as a good indicator for
dust extinction in the AGN broad-line region; this is especially true
for radio-quiet AGN with regular emission-line profiles, which
constitute the vast majority of the AGN population.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 104 446 Properties of blue AGNs
table2.dat 80 446 Hα and Hβ broad-line profile measurements
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See also:
II/282 : The SDSS Photometric Catalog, Release 6 (Adelman-McCarthy+, 2007)
http://www.sdss.org : SDSS Home Page
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 18 A18 --- SDSS Object J2000.0 name (HHMMSS.ss+DDMMSS.s)
20- 26 F7.5 --- z SDSS spectroscopic redshift
28- 32 F5.2 10-7W L5100 Monochromatic luminosity at 5100Å
34- 39 F6.1 10-20W/m2 F(Hbn) Hβ narrow component flux (1)
41- 47 F7.1 10-20W/m2 F(Hbb) Hβ broad component flux (2)
49- 54 F6.1 10-20W/m2 F(Han) Hα narrow component flux (3)
56- 62 F7.1 10-20W/m2 F(Hab) Hα broad component flux (3)
64- 67 F4.2 --- alpha1 Continuum slope blueward of 5600Å,
F(λ)∝λ-α1 (2)
69- 72 F4.2 --- alpha2 Continuum slope redward of 5600Å,
F(λ)∝λ-α2 (2)
74- 78 F5.2 mag FUV ?=99.99 GALEX calibrated magnitude (AB)
in FUV band (135-175nm) (4)(5)
80- 84 F5.2 mag NUV ?=99.99 GALEX calibrated magnitude (AB)
in NUV band (175-280nm) (4)(5)
86- 90 F5.2 mag imag SDSS i-band magnitude (AB) (4)
92- 96 F5.3 mag E(B-V) Galactic colour excess derived from
Schlegel et al. (1998ApJ...500..525S 1998ApJ...500..525S)
98 A1 --- l_Sint Limit flag on Sint
99-104 F6.2 mJy Sint ? Integrated flux density at 20cm
detected by FIRST (6)
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Note (1): Typical error is 6%. Units in 10-17erg/cm2/s
Note (2): Typical error is 8%. Units in 10-17erg/cm2/s
Note (3): Typical error is 5%. Units in 10-17erg/cm2/s
Note (4): Uncorrected for Galactic extinction.
Note (5): A '99.99' is given for sources that are covered yet not detected
by GALEX, and a blank is given for 185 sources that are not covered by
GALEX
Note (6): The detection limit of 1mJy is adopted as the upper limit for 336
objects that are covered yet not detected by FIRST and a blank is
given for 42 objects that are not covered by FIRST.
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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- 18 A18 --- SDSS Object J2000.0 name (HHMMSS.ss+DDMMSS.s)
20- 26 F7.1 km/s FWHMb Broad Hβ FWHM
28- 33 F6.1 km/s sigmab Broad Hβ line dispersion
35- 39 F5.2 --- AIb Broad Hβ asymmetry index (1)
41- 44 F4.2 --- SIb Broad Hβ shape index (2)
46- 49 F4.2 --- KI1b Broad Hβ Kurtosis index (3)
51- 57 F7.1 km/s FWHMa Broad Hα FWHM
59- 64 F6.1 km/s sigmaa Broad Hα line dispersion
66- 70 F5.2 --- AIa Broad Hα asymmetry index (1)
72- 75 F4.2 --- SIa Broad Hα shape index (2)
77- 80 F4.2 --- KI1a Broad Hα Kurtosis index (3)
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Note (1): Asymmetry index (AI) defined as in De Robertis (1985ApJ...289...67D 1985ApJ...289...67D)
Note (2): shape index (SI) as in Boroson & Green (1992ApJS...80..109B 1992ApJS...80..109B)
Note (3): kurtosis index (KI1) in Marziani et al. (1996ApJS..104...37M 1996ApJS..104...37M)
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 19-Jan-2009