J/A+A/570/A96 GTC spectra of z∼2.3 quasars (Sulentic+, 2014)
GTC spectra of z∼2.3 quasars: comparison with local luminosity analogs.
Sulentic J.W., Marziani P., del Olmo A., Dultzin D., Perea J., Negrete C.A.
<Astron. Astrophys. 570, A96 (2014)>
=2014A&A...570A..96S 2014A&A...570A..96S
ADC_Keywords: QSOs ; Atlases ; Spectrophotometry
Keywords: quasars: emission lines - quasars: supermassive black holes -
ISM: abundances - line: profiles - cosmology: observations
Abstract:
The advent of 8-10m class telescopes for the first time makes it
possible to compare in detail quasars with similar luminosity and very
different redshifts.
We conducted a search for z-dependent gradients in line-emission
diagnostics and derived physical properties by comparing, in a narrow
bolometric luminosity range (logL∼46.1±0.4erg/s), some of the most
luminous local z<0.6 quasars with some of the lowest luminosity
sources yet found at redshift z=2.1-2.5.
Moderate signal-to-noise ratio spectra for 22 high-redshift sources
were obtained with the 10.4m Gran Telescopio Canarias (GTC), for which
the HST (largely the Faint Object Spectrograph) archive provides a
low-redshift control sample. We compared the spectra in the context of
the 4D Eigenvector 1 formalism, meaning that we divided both source
samples into highly accreting population A and population B sources
accreting at a lower rate.
CIV λ1549, the strongest and most reliable diagnostic line,
shows very similar properties at both redshifts, which confirms the
CIV λ1549 profile differences at high redshift between
populations A and B, which are well established in local quasars. The
CIV λ1549 blueshift that appears quasi-ubiquitous in higher L
sources is found in only half (population A) of the quasars observed
in the two samples. A CIV λ1549 evolutionary Baldwin effect is
certainly disfavored. We find evidence for lower metallicity in the
GTC sample that may point toward a gradient with z. No evidence for a
gradient in black hole mass or Eddington ratio is found.
Spectroscopic differences established at low z are also present in
much higher redshift quasars. Our results on the CIV λ1549
blueshift suggest that it depends both on source luminosity and
Eddington ratio. Given that our samples involve sources with very
similar luminosity, the evidence for a systematic metallicity
decrease, if real, points toward an evolutionary effect. Our samples
are not large enough to effectively constrain possible changes of
black hole mass or Eddington ratio with redshift. The two samples
appear representative of a slowly evolving quasar population that is
most likely present at all redshifts.
Description:
Spectroscopic data for 22 intermediate redshift quasars are identified
in Table 1. Actual data files are in FITS format in the spectra
sub-directory. Each individual spectrum cover the spectral range
360-770 nm. Units are in wavelength in Angstrom, and specific flux in
erg/s/cm2/Angstrom (pW/m3) in the observed frame (i.e., before
redshift correction).
Full object name (OBJECT), total exposure time (EXPTIME),
number of coadded individual spectra (NUM_IMAG), and observation date
(DATE-OBS) are reported as records in the FITS header of each spectrum
(as in Table 2 of the paper).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table12.dat 94 22 List of the program quasars and log of
observations (tables 1 and 2 of the paper)
sp/* . 22 Individual FITS spectra
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Byte-by-byte Description of file: table12.dat
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Bytes Format Units Label Explanations
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1- 25 A25 --- Name Quasar identification code
27- 30 F4.1 mag Vmag Indicative V magnitude as reported by
Veron-Cetty & Veron 2010 (VII/258)
32- 37 F6.4 --- z [1.5/2.5] Redshift
39- 44 F6.4 --- e_z 1-σ confidence level redshift uncertainty
46- 50 F5.1 mag BMAG Absolute B magnitude at z=0 as tabulated
by Veron-Cetty & Veron (2010, Cat. VII/258)
52- 61 A10 "date" ObsDate Observation date
63- 66 I4 s ExpTime [2400/3250] Exposure time
68 I1 --- Nexp [4/5] Number of exposures
70- 71 I2 --- S/N [5/40] Signal-to-noise ratio at 1450Å
73- 76 F4.2 arcsec Slit [0.8/1.3] Slit width
78- 81 F4.2 arcsec Seeing [0.8/1.6] Seeing
83- 94 A12 --- FileName Name of FITS file containing the spectrum in
subdirectory sp
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Acknowledgements:
Paola Marziani, paola.marziani(at)oapd.inaf.it
(End) Patricia Vannier [CDS] 01-Sep-2014