J/MNRAS/465/2120 Correcting CIV-based virial black hole masses (Coatman+, 2017)
Correcting C IV-based virial black hole masses.
Coatman L., Hewett P.C., Banerji M., Richards G.T., Hennawi J.F.,
Prochaska J.X.
<Mon. Not. R. Astron. Soc., 465, 2120-2142 (2017)>
=2017MNRAS.465.2120C 2017MNRAS.465.2120C (SIMBAD/NED BibCode)
ADC_Keywords: QSOs ; Spectroscopy ; Redshifts
Keywords: galaxies: evolution
Abstract:
The CIVλλ1498,1501 broad emission line is visible in
optical spectra to redshifts exceeding z∼5. CIV has long been known to
exhibit significant displacements to the blue and these 'blueshifts'
almost certainly signal the presence of strong outflows. As a
consequence, single-epoch virial black hole (BH) mass estimates
derived from CIV velocity widths are known to be systematically biased
compared to masses from the hydrogen Balmer lines. Using a large
sample of 230 high-luminosity (LBol=1045.5-1048erg/s), redshift
1.5<z<4.0 quasars with both CIV and Balmer line spectra, we have
quantified the bias in CIV BH masses as a function of the CIV
blueshift. CIV BH masses are shown to be a factor of 5 larger than the
corresponding Balmer-line masses at C IV blueshifts of 3000km/s and
are overestimated by almost an order of magnitude at the most extreme
blueshifts, ?=5000km/s. Using the monotonically increasing
relationship between the CIV blueshift and the mass ratio
BH(CIV)/BH(Hα), we derive an empirical correction to all CIV BH
masses. The scatter between the corrected CIV masses and the Balmer
masses is 0.24dex at low CIV blueshifts (∼0km/s) and just 0.10dex at
high blueshifts (∼3000km/s), compared to 0.40dex before the
correction. The correction depends only on the CIV line properties -
i.e. full width at half-maximum and blueshift - and can therefore be
applied to all quasars where CIV emission line properties have been
measured, enabling the derivation of unbiased virial BH-mass estimates
for the majority of high-luminosity, high-redshift, spectroscopically
confirmed quasars in the literature.
Description:
The aim of this work is to measure empirically the systematic bias in
CIV-based virial BH-mass estimates for high-z quasars as a function of
the CIV emission line blueshift. The basis for the CIV blueshift-based
correction is a large sample of quasars, where it is possible to make
a direct comparison of the CIV line width with the line width of the
low-ionization Balmer lines Hα and Hβ, which are believed
to provide reliable proxies for the virial velocity. Such an approach
has not been possible hitherto as spectra that cover both the
observed-frame optical (where the redshifted CIV appears) and
near-infrared (where Hβ and Hα lie) are required.
We have compiled a sample of 307 quasars at redshifts 1.5<z<4 with
both optical and near-infrared spectra to enable such a comparison to
be performed. Reliable emission line properties were measured for 230
quasars, with 164 possessing Hα line measurements
and 144 Hβ line measurements.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 158 230 Emission line properties from our parametric
model fits
tableb.dat 124 230 Observational properties (Tables B1-B7)
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See also:
VII/241 : The 2dF QSO Redshift Survey (Croom+ 2004)
VII/279 : SDSS quasar catalog: twelfth data release (Paris+, 2017)
J/AJ/131/1 : Binary quasars in the SDSS (Hennawi+, 2006)
J/ApJ/719/1672 : SDSS binary quasars at high redshift. I. (Hennawi+, 2010)
J/ApJ/753/125 : NIR spectroscopy follow-up of 60 SDSS-DR7 QSOs (Shen+, 2012)
J/A+A/556/A141 : ESO-UVES Advanced Data Products (EUADP) sample (Zafar+, 2013)
J/ApJ/776/136 : QPQ VI. HI absorption of z∼2 quasars (Prochaska+, 2013)
J/ApJ/817/55 : NIR spectroscopy of 1.5<z<3.5 broad-band QSOs (Shen, 2016)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 19 A19 --- Name Catalogue name (JHHMMSS.ss+DDMMSS.s) (NAME)
21- 26 F6.1 km/s FWHMBHa ? FWHM of broad Hα line
(FWHMBROADHA)
28- 33 F6.1 km/s e_FWHMBHa ? rms uncertainty on (FWHMBROADHA_ERR)
35- 40 F6.1 km/s sigmaBHa ? Dispersion of broad Hα
line (SIGMABROADHA)
42- 47 F6.1 km/s e_sigmaBHa ? rms uncertainty on (SIGMABROADHA_ERR)
49- 54 F6.4 --- zBHa ? Redshift from broad Hα line
(ZBROADHA)
56- 62 F7.1 km/s FWHMBHb ? FWHM of broad Hβ line (FWHMBROADHB)
64- 69 F6.1 km/s e_FWHMBHb ? rms uncertainty on (FWHMBROADHB_ERR)
71- 76 F6.1 km/s sigmaBHb ? Dispersion of broad Hβ line
(SIGMABROADHB)
78- 83 F6.1 km/s e_sigmaBHb ? rms uncertainty on (SIGMABROADHB_ERR)
85- 90 F6.4 --- zBHb ? Redshift from broad Hβ line
(ZBROADHB)
92- 98 F7.1 km/s FWHMCIV FWHM of CIV doublet (FWHM_CIV)
100-105 F6.1 km/s e_FWHMCIV rms uncertainty on (FWHMCIVERR)
107-112 F6.1 km/s sigmaCIV Dispersion of CIV doublet (SIGMA_CIV)
114-118 F5.1 km/s e_sigmaCIV rms uncertainty on (SIGMACIVERR)
120-125 F6.1 km/s blueCIVHa ? Blueshift of CIV relative to centroid of
broad Hα (BLUESHIFTCIVHA)
127-131 F5.1 km/s e_blueCIVHa ? rms uncertainty on (BLUESHIFTCIVHA_ERR)
133-138 F6.1 km/s blueCIVHb ? Blueshift of CIV relative to centroid of
broad Hβ (BLUESHIFTCIVHB)
140-144 F5.1 km/s e_blueCIVHb ? rms uncertainty on (BLUESHIFTCIVHB_ERR)
146-151 F6.3 [10-7W] logL5100 Monochromatic continuum luminosity at
5100Å (LOGL5100)
153-158 F6.3 [10-7W] logL1350 Monochromatic continuum luminosity at
1350Å (LOGL1350)
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Byte-by-byte Description of file: tableb.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 A2 --- Tab Table number (B1-B7) (1)
4- 22 A19 --- Name Name (JHHMMSS.ss+DDMMSS.s)
24- 38 A15 --- Inst Instrument or ESO programme identification
40- 49 A10 --- Obs.Date Observation date
50 A1 --- --- [/]
51- 60 A10 --- Obs.Date2 Second observation date
63- 66 I4 s Texp ? Exposure time
67- 69 A3 --- n_Texp [(H) ] Note on Texp
70- 73 I4 s Texp2 ? Second exposure time
74- 76 A3 --- n_Texp2 [(K) ] Note on Texp2
78- 82 F5.2 --- S/NHa ? S/N measured in the continuum adjacent to
Hα, per pixel
84- 88 F5.2 --- S/NHb ? S/N measured in the continuum adjacent to
Hβ, per pixel
90- 97 A8 --- r_S/N Source of optical spectra
99-104 F6.2 --- S/NCIV S/N measured in the continuum adjacent to CIV,
per pixel
107-112 F6.4 --- z Redshift
113 A1 --- r_z [abdez] Redshift reference if not from Hewett
and Wild (2010, Cat. J/MNRAS/405/2302) (2)
115-120 F6.3 mag imag SDSS i magnitude except note in n_imag
121 A1 --- n_imag [bce] Note in not SDSS i band in imag (3)
123-124 I2 --- Radio [-1/2] Radio classification from FIRST (4)
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Note (1): Informations as follows:
B1 = Observational properties of the 15 quasars selected from Paper I
(Coatman et al., 2016MNRAS.461..647C 2016MNRAS.461..647C) and observed in the near-infrared
with the LIRIS spectrograph on the WHT.
B2 = Observational properties of the quasars taken from Shen & Liu (2012,
Cat. J/ApJ/753/125) and Shen (2016, Cat. J/ApJ/817/55) and observed in
the near-infrared with the TRIPLESPEC spectrograph on the ARC 3.5m
telescope (34 quasars) and the FIRE spectrograph on the Magellan-Baade
telescope (23 quasars). The typical exposure times were 1.0-1.5h for
TRIPLESPEC and 45min for FIRE.
B3 = Observational properties of the quasars taken from the 'QPQ' catalogue
(Hennawi et al., 2006, Cat. J/AJ/131/1; 2010, Cat. J/ApJ/719/1672).
22 quasars were observed with GNIRS on the Gemini North telescope,
four with ISAAC on the VLT, 11 with NIRI also on Gemini North and nine
with XSHOOTER, again, on the VLT.
B4 = Observational properties of the 37 quasars found in the ESO archive and
observed in the near-infrared with the SINFONI spectrograph on the VLT.
The sample is divided by the ESO programme identification. Optical
spectra are from the SDSS/BOSS and the Hamburg/ESO survey (HES).
B5 = Observational properties of 28 quasars observed in the near-infrared with
the SOFI spectrograph on the ESO NTT as part of a programme targeting
quasars with archival UVES spectra.
B6 = Observational properties of 27 quasars observed in the near-infrared with
the SOFI spectrograph on the ESO NTT as part of a programme targeting
quasars with large CIV blueshifts.
B7 = Observational properties of 32 quasars observed in the near-infrared with
the TRIPLESPEC spectrograph on the Palomar 200-inch Hale telescope.
Note (2): Redshift reference as follows:
a = Paris et al. (2017A&A...597A..79P 2017A&A...597A..79P, Cat. VII/279)
b = Croom et al. (2004MNRAS.349.1397C 2004MNRAS.349.1397C, Cat. VII/241)
d = Prochaska et al. (2013, Cat. J/ApJ/776/136)
e = CIV-based redshift, measured in Hamburg/ESO spectra
z = Zafar, Popping & Peroux (2013A&A...556A.140Z 2013A&A...556A.140Z, See Cat. J/A+A/556/A141)
Note (3): When not i mag, note as follows:
b = K-band magnitude (Vega)
c = when BJ magnitude (Vega). For a description of the BJ passband see
appendix A in Maddox & Hewett (2006MNRAS.367..717M 2006MNRAS.367..717M)
e = V-band magnitude (Vega)
Note (4): radio classification from FIRST as follows:
-1 = not in footprint
0 = radio undetected
1 = core-dominated radio-detected
2 = lobe-dominated radio-detected
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History:
From electronic version of the journal
References:
Coatman et al., Paper I 2016MNRAS.461..647C 2016MNRAS.461..647C
(End) Patricia Vannier [CDS] 04-Sep-2018