J/MNRAS/504/5556 X-ray properties of 26 high-luminosity quasars (Timlin+, 2021)
What controls the UV-to-X-ray continuum shape in quasars?
Timlin J.D., Brandt W.N., Laor A.
<Mon. Not. R. Astron. Soc. 504, 5556-5574 (2021)>
=2021MNRAS.504.5556T 2021MNRAS.504.5556T (SIMBAD/NED BibCode)
ADC_Keywords: Active gal. nuclei ; QSOs ; X-ray sources ; Redshifts ;
Equivalent widths
Keywords: galaxies: active - quasars: emission lines - quasars: general -
X-rays: general
Abstract:
We present an investigation of the interdependence of the
optical-to-X-ray spectral slope (aox), the HeII equivalent-width (EW),
and the monochromatic luminosity at 2500Å (L2500). The values of
αox and HeII EW are indicators of the strength/shape of the
quasar ionizing continuum, from the ultraviolet (UV; 1500-2500Å),
through the extreme ultraviolet (EUV;300-50Å), to the X-ray (2keV)
regime. For this investigation, we measure the HeII EW of 206
radio-quiet quasars devoid of broad absorption lines that have
high-quality spectral observations of the UV and 2keV X-rays. The
sample spans wide redshift (z∼0.13-3.5) and luminosity
(logL2500∼29.2-32.5erg/s/Hz) ranges. We recover the well-known
αox-L2500 and HeII EW-L2500 anti-correlations, and we find
a similarly strong correlation between αox and HeII EW, and
thus the overall spectral shape from the UV, through the EUV, to the
X-ray regime is largely set by luminosity. A significant
αox-HeII EW correlation remains after removing the
contribution of L2500 from each quantity, and thus the emission in
the EUV and the X-rays are also directly tied. This set of relations
is surprising, since the UV, EUV, and X-ray emission are expected to
be formed in three physically distinct regions. Our results indicate
the presence of a redshift-independent physical mechanism that couples
the continuum emission from these three different regions, and thus
controls the overall continuum shape from the UV to the X-ray regime.
Description:
In this work, we presented the first, large-scale investigation of the
joint relationships between αox, HeII EW, and L2500. We
gathered 206 quasars that have high-quality spectral coverage of the
rest-frame UV and have sensitive X-ray coverage with Chandra or
XMM-Newton; these span wide ranges of both luminosity and redshift.
Table A1: The HeII EW sample data.
Table B1: X-ray properties of the 26 high-luminosity quasars from
Chandra Cycle 13.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
tablea1.dat 145 206 The HeII EW sample data
tableb1.dat 591 26 X-ray properties of the 26 high-luminosity
(High-L) quasars from Chandra Cycle 13
--------------------------------------------------------------------------------
Byte-by-byte Description of file: tablea1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 7 A7 --- Sample Name of the original sample (Sample) (1)
9- 26 A18 --- Name ID from the original sample (ID) (2)
28- 46 F19.15 deg RAdeg Right ascension (J2000) (RA)
48- 66 F19.15 deg DEdeg Declination (J2000) (DEC)
68- 75 F8.6 --- z Redshift (z)
77- 82 F6.3 [0.1nm] log(EWHeII) log of the rest-frame HeII equivalent
width (log10(HeII_EW))
84- 89 F6.4 [0.1nm] e_log(EWHeII) Uncertainty in log(HeIIEW) (err_logHeII)
91 I1 --- HeIIdet [0/1] HeII line detection (HeII_det)
93- 98 F6.3 [10-7W/Hz] log(L2500) log rest-frame 2500 angstrom luminosity
(log10(L2500))
100-105 F6.3 [mW/m2/Hz] log(L2keV) log of rest-frame 2keV luminosity
(log10(L2keV))
107-113 F7.4 [mW/m2/Hz] e_log(L2keV) []?=- Uncertainty in log(L2keV)
(err_log10(L2keV))
115-119 F5.2 --- aox X-ray-to-optical index (aox)
121-125 F5.3 --- e_aox uncertainty in aox (err_aox)
127 I1 --- Xdet Detected in Xrays (Xdet)
129-135 F7.5 [0.1nm] logEWCIV log rest-frame CIV EW (angstrom (CIV_EW)
137-145 F9.6 [0.1nm] e_logEWCIV [] Uncertainty in logCIVEW (CIVEWERR)
--------------------------------------------------------------------------------
Note (1): Samples are High-L, PG and SDSS-RM.
Note (2): For High-L sample, HHMMSS.ss+DDMMSS.s, SDSS JHHMMSS.ss+DDMMSS.s,
for SDSS-RM sample, NNN, for PG sample HHMM+DDd, PG HHMM+DDd.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: tableb1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 18 A18 --- Name SDSS Name (NAME)
20- 38 F19.15 deg RAdeg Right ascension (J2000) (RA)
40- 58 F19.16 deg DEdeg Declination (J2000) (DEC)
60- 67 F8.6 --- z Redshift (Z)
69- 74 F6.3 [cm/s2] logNH Galactic column density (LOGNH)
76- 81 F6.3 mag imag Observed i-band magnitude (imag_obs)
83- 90 F8.4 mag iMAG Absolute i-band magnitude
(corrected to z=2) (Mi_Z2)
92- 96 A5 --- ObsID Chandra observation ID (ObsID)
98-105 F8.6 arcmin Theta Chandra off-axis angle (arcmin) (THETA)
107-113 F7.2 s EtimeS Soft-band effective exposure time
(Exposureeffsoft)
115-121 F7.2 s EtimeH Hard-band effective exposure time
(Exposureeffhard)
123-129 F7.2 s EtimeF Full-band effective exposure time
(Exposureefffull)
131-142 E12.6 --- Pbsoft Binomial probability of detection (soft)
(Pb_soft)
144-155 E12.6 --- Pbhard Binomial probability of detection (hard)
(Pb_hard)
157-168 E12.6 --- Pbfull Binomial probability of detection (full)
(Pb_full)
170-171 I2 ct SoftCTr Raw source counts (soft) (Softctsraw)
175 I1 ct SoftCTbgr Raw background counts (soft) (Softbgraw)
179-186 F8.5 ct SoftCT Soft-band net counts (or 90% confidence
(Soft_cts)
188-195 F8.6 ct e_SoftCT Soft lower limit (Softctsmerr)
197-204 F8.6 ct E_SoftCT Soft upper limit (Softctsperr)
206-207 I2 ct HardCTr Raw source counts (hard) (Hardctsraw)
211 I1 ct HardCTbgr Raw background counts (hard) (Hardbgraw)
215-222 F8.5 ct HardCT Hard-band net counts (or 90% confidence
(Hard_cts)
224-231 F8.6 ct e_HardCT Hard lower limit (Hardctsmerr)
233-239 F7.5 ct E_HardCT Hard upper limit (Hardctsperr)
241-242 I2 ct FullCTr Raw source counts (full) (Fullctsraw)
246-247 I2 ct FullCTbgr Raw background counts (full) (Fullbgraw)
251-259 F9.5 ct FullCT Full-band net counts (or 90% confidence)
(Full_cts)
261-269 F9.6 ct e_FullCT Full lower limit (Fullctsmerr)
271-279 F9.6 ct E_FullCT Full upper limit (Fullctsperr)
281-291 F11.4 cm2.s SRC-expS Mean exposure-map pixel value of the ion
(soft band) (MEANSRCEXP_s)
293-304 F12.5 cm2.s BG-expS Mean exposure-map pixel value of the
regions (soft band) (MEANBGEXP_s)
306-317 F12.5 cm2.s SRC-expH Mean exposure-map pixel value of the ions
(hard band) (MEANSRCEXP_h)
319-329 F11.4 cm2.s BG-expH Mean exposure-map pixel value of the
background regions (hard band)
(MEANBGEXP_h)
331-342 F12.5 cm2.s SRC-expF Mean exposure-map pixel value of the ions
(full band) (MEANSRCEXP_f)
344-355 F12.5 cm2.s BG-expF Mean exposure-map pixel value of the
regions (full band) (MEANBGEXP_f)
357-363 F7.4 --- HR Hardness ratio (HRat)
365-373 F9.5 --- e_HR Hardness ratio low limit (HR_lolim)
375-381 F7.5 --- E_HR Hardness ratio upper limit (HR_uplim)
383-385 F3.1 --- Gamma Power-law photon index (dual-band
detections) or limit
(single-band detection) (Gamma)
387-389 F3.1 --- e_Gamma Power-law photon index lower limit
(Gamma_lolim)
391-393 F3.1 --- E_Gamma Power-law photon index upper limit
(Gamma_uplim)
395-405 F11.9 ct/s SoftCR Soft-band count rate (SoftCountrate)
407-418 F12.10 ct/s e_SoftCR Soft-band count rate lower limit
(SoftCountrate_merr)
420-431 F12.10 ct/s E_SoftCR Soft-band count rate upper limit
(SoftCountrate_perr)
433-443 F11.9 ct/s HardCR Hard-band count rate (HardCountrate)
445-456 F12.10 ct/s e_HardCR Hard-band count rate lower limit
(HardCountrate_merr)
458-469 F12.10 ct/s E_HardCR Hard-band count rate upper limit
(HardCountrate_perr)
471-481 F11.9 ct/s FullCR Full-band count rate (FullCountrate)
483-494 F12.10 ct/s e_FullCR Full-band count rate lower limit
(FullCountrate_merr)
496-507 F12.10 ct/s E_FullCR Full-band count rate upper limit
(FullCountrate_perr)
509-519 E11.6 mW/m2/Hz SoftS Observed flux density at rest-frame 2keV
(Soft_density)
521-531 E11.6 mW/m2/Hz e_SoftS Observed flux density at rest-frame 2keV
lower limit (Softdensitylolim)
533-543 E11.6 mW/m2/Hz E_SoftS Observed flux density at rest-frame 2keV
upper limit (Softdensityuplim)
545-555 E11.6 mW/m2/Hz f2500 Observed flux density at rest-frame
2500Å (f2500)
557-562 F6.3 [10-7W/Hz] logL2500 Rest-frame 2500 Å monochromatic
luminosity (logL_2500)
564-571 F8.5 --- aox Observed X-ray-to-optical index (alphaox)
573-581 F9.6 --- e_aox [] Observed aox lower limit (alphaox_lolim)
583-591 F9.6 --- E_aox [] Observed aox upper limit (alphaox_uplim)
--------------------------------------------------------------------------------
Acknowledgements:
John Timlin, jdtimlin3(at)gmail.com
(End) John Timlin [Penn State University], Patricia Vannier [CDS] 21-Apr-2021