J/ApJ/860/41 Spectral & environment properties of z∼2 QSO pairs (Lusso+, 2018)
The spectral and environment properties of z∼2.0-2.5 quasar pairs.
Lusso E., Fumagalli M., Rafelski M., Neeleman M., Prochaska J.X.,
Hennawi J.F., O'Meara J.M., Theuns T.
<Astrophys. J., 860, 41 (2018)>
=2018ApJ...860...41L 2018ApJ...860...41L
ADC_Keywords: QSOs; Intergalactic medium; Photometry, SDSS; Redshifts;
Spectra, ultraviolet
Keywords: accretion, accretion disks ; galaxies: active ; intergalactic medium ;
quasars: absorption lines ; quasars: general
Abstract:
We present the first results from our survey of intervening and
proximate Lyman limit systems (LLSs) at z∼2.0-2.5 using the Wide Field
Camera 3 on board the Hubble Space Telescope. The quasars in our
sample are projected pairs with proper transverse separations
R⊥≤150kpc and line-of- sight velocity separations ≲11000km/s.
We construct a stacked ultraviolet (rest-frame wavelengths
700-2000Å) spectrum of pairs corrected for the intervening Lyman
forest and Lyman continuum absorption. The observed spectral composite
presents a moderate flux excess for the most prominent broad emission
lines, a ∼30% decrease in flux at λ=800-900Å compared to a
stack of brighter quasars not in pairs at similar redshifts, and lower
values of the mean free path of the HI ionizing radiation for pairs
(λmfp912=140.7±20.2h70-1Mpc) compared to single
quasars (λmfp912=213.8±28h70-1Mpc) at the average
redshift z∼2.44. From the modeling of LLS absorption in these pairs,
we find a higher (∼20%) incidence of proximate LLSs with
logNHI≥17.2 at δv<5000km/s compared to single quasars (∼6%).
These two rates are different at the 5σ level. Moreover, we find
that optically thick absorbers are equally shared between foreground
and background quasars. Based on these pieces of evidence, we conclude
that there is a moderate excess of gas-absorbing Lyman continuum
photons in our closely projected quasar pairs compared to single
quasars. We argue that this gas arises mostly within large-scale
structures or partially neutral regions inside the dark matter halos
where these close pairs reside.
Description:
The sample of quasars observed in our HST program is drawn from a
compilation of quasar pairs with g*<21mag (Hennawi+ 2006, J/ApJ/651/61 ;
2010, J/ApJ/719/1672 and Findlay+ 2018ApJS..236...44F 2018ApJS..236...44F), selected from
the SDSS/BOSS footprints in the redshift range z∼2.0-2.5.
Our HST program includes 47 quasar pairs and four additional single
quasars observed within the survey, leading to a total of 104 quasars
(111 observations).
Each quasar pair was observed with HST WFC3/UVIS-G280 grism for one
orbit between 2016 September and 2017 March 12 (Cycle 23,
program ID 14127, PI: Fumagalli).
Optical spectra were obtained for a fraction of our quasar pairs from
a variety of instruments and thus have different wavelength coverage
and resolution. High S/N spectra were taken for 27 quasars using the
Echellette Spectrograph and Imager (ESI) at the Keck II telescope and
the moderate-resolution Magellan Echellette (MagE) optical
spectrograph. Twelve quasars have medium- to low-resolution optical
spectroscopy from several telescopes, such as the 6.5m Multiple Mirror
Telescope (MMT), Calar Alto Observatory (CAHA), Keck, the 2.1m
telescope at the Kitt Peak National Observatory (KPNO), and Gemini
(see Table 1).
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 127 111 Full sample of WFC3 quasars
table2.dat 47 212 WFC3 stacked spectrum corrected for IGM absorption
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See also:
B/hst : HST Archived Exposures Catalog (STScI, 2007)
J/ApJ/475/469 : Composite HST Spectrum of Quasars (Zheng+ 1997)
J/A+A/417/515 : I Zw 1 unusual emission line spectrum (Veron-Cetty+, 2004)
J/ApJ/651/61 : Opt. thick absorbers near luminous QSOs (Hennawi+, 2006)
J/AJ/131/1 : Binary quasars in the SDSS (Hennawi+, 2006)
J/AJ/131/2766 : Quasar luminosity function from SDSS-DR3 (Richards+, 2006)
J/ApJ/678/635 : Spectroscopy of quasar binary candidates (Myers+, 2008)
J/ApJ/693/1554 : Double QSOs: merger scenarios (Foreman+, 2009)
J/ApJ/719/1672 : SDSS binary quasars at high redshift. I. (Hennawi+, 2010)
J/ApJ/718/392 : SDSS Lyman limit systems at z∼3.5 (Prochaska+, 2010)
J/ApJS/195/16 : HST survey for Lyman limit systems. I. (O'Meara+, 2011)
J/ApJ/736/42 : HST QSO Catalog (Ribaudo+, 2011)
J/ApJS/194/45 : QSO properties from SDSS-DR7 (Shen+, 2011)
J/ApJ/728/23 : GALEX UV-bright high-redshift quasars (Worseck+, 2011)
J/ApJ/775/78 : Lyman limit absorption syst. in z∼3 QSOs (Fumagalli+, 2013)
J/ApJ/765/137 : HST survey for Lyman limit systems. II. (O'Meara+, 2013)
J/ApJ/776/136 : QPQ VI. HI absorption of z∼2 quasars (Prochaska+, 2013)
J/ApJ/794/75 : HST-COS UV spectra observations of AGNs (Stevans+, 2014)
J/MNRAS/445/1745 : Giant Gemini GMOS survey. I. (Worseck+, 2014)
J/MNRAS/449/4204 : WFC3/UVIS quasar-stacked spectrum at z≃2.4 (Lusso+, 2015)
J/AJ/150/31 : Photometry & redshifts of gal. in the UDF (Rafelski+, 2015)
J/ApJ/817/111 : HST/COS survey of z<0.9 AGNs. I. (Danforth+, 2016)
J/MNRAS/464/3882 : Mergers and galaxy-galaxy interactions (Weston+, 2017)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 24 A24 --- Name Identifier
26- 35 F10.6 deg RAdeg Right Ascension in decimal degrees (J2000)
37- 46 F10.6 deg DEdeg Declination in decimal degrees (J2000)
48- 52 F5.2 mag umag [18.2/21.9]? SDSS u* band model magnitude
54- 58 F5.2 mag gmag [18.2/21.6]? SDSS g* band model magnitude
60- 64 F5.2 mag rmag [18.1/21.7]? SDSS r* band model magnitude
66- 70 F5.2 mag imag [17.9/22]? SDSS i* band model magnitude
72- 76 F5.2 mag zmag [17.6/22]? SDSS z* band model magnitude
78- 82 F5.1 kpc Rperp [8.7/151.4]? Transverse proper separation
84- 88 F5.2 arcsec ASep [1/17.6]? Angular separation
90- 94 F5.3 --- z [1.8/2.7] Spectroscopic redshift estimate
96- 99 I4 km/s sigma [0/1068] Uncertainty in z
101-114 A14 --- Line Emission line used to determine z
116-119 A4 --- Inst Survey/instrument/telescope used
to determine z (1)
121-125 A5 --- Note An additional note
127 A1 --- f_Note Flag on Note (2)
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Note (1): The relative reference is provided in the case a source has already
a redshift available from the literature.
HE0230-2130 = Anguita et al. (2008A&A...481..615A 2008A&A...481..615A),
QSO J1017-207 = Claeskens et al. (1996A&A...305L...9C 1996A&A...305L...9C);
Surdej et al. (1997A&A...327L...1S 1997A&A...327L...1S).
Note (2):
* = Lower signal-to-noise lense spectrum that has been excluded from
the stacking analysis.
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Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 11 F11.6 0.1nm lambda [688.5/1994.7] Rest-frame wavelength; Angstroms
13- 20 F8.6 --- FAll [0.6/4.5] Mean all WFC3 quasar flux
per Angstrom (1)
22- 29 F8.6 --- e_FAll [0.0001/0.4] Uncertainty from bootstrap in FAll
31- 38 F8.6 --- FPairs [0.6/4.5] Mean pair only quasar flux
per Angstrom (1)
40- 47 F8.6 --- e_FPairs [0.0001/0.4] Uncertainty from bootstrap in FPair
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Note (1): IGM corrected, normalized to the flux at 1450 Angstroms. 157 quasars
in the all WFC3 sample and 94 quasars in the WFC3 pairs only sample.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 21-Jun-2019