J/A+A/701/A144 Stacked X-ray spectra of eROSITA AGN (Chen+, 2025)
The average soft X-ray spectra of eROSITA active galactic nuclei.
Chen S.-J., Buchner J., Liu T., Hagen S., Waddell S.G.H., Nandra K.,
Salvato M., Igo Z., Aydar C., Merloni A., Ni Q., Kang J.-L., Cai Z.-Y.,
Wang J.-X., Li R., Ramos-Ceja M.E., Sanders J., Georgakakis A., Zhang Y.
<Astron. Astrophys. 701, A144 (2025)>
=2025A&A...701A.144C 2025A&A...701A.144C (SIMBAD/NED BibCode)
ADC_Keywords: Active gal. nuclei ; X-ray sources ; Spectroscopy
Keywords: galaxies: active - X-rays: galaxies
Abstract:
Active galactic nuclei (AGN) stand as extreme X-ray emitters where
disk-corona interplay shapes their spectral energy distribution. The
soft X-ray excess, a unique feature of AGN in the 0.5-2.0keV,
encodes critical information on the "warm corona" structure
bridging the disk and hot corona. However, the systematic evolution of
this feature with fundamental accretion parameters in large AGN
samples - particularly those studied through the spectral stacking
technique - remains observationally unconstrained.
The eROSITA All-Sky Survey (eRASS:5) provides an unprecedented sample
to statistically map AGN spectral properties. We present a
multiwavelength investigation of how the average AGN X-ray spectra
evolve with accretion parameters (αox, LUV, λEdd,
MBH), and we explore the disk-corona connection by further combining
stacked UV data.
We have developed Xstack, a novel X-ray spectral stacking code that
consistently stacks rest-frame pulse invariant (PI) spectra and
associated responses using optimized response weighting to preserve
spectral shapes. With Xstack, we stacked 17929 AGNs ("spec-z"
sample, total exposure ∼23Ms) with similar X-ray loudness, αox,
and UV luminosity, LUV, and 4159 AGNs ("BH-mass" sample,
∼3Ms) with similar Eddington ratios, λEdd, and black hole
masses, MBH. We analyzed the resulting stacked X-ray spectra with a
phenomenological model for both samples. We further fit the stacked
optical-UV X-ray SED with the physical AGNSED model on a
3x3MBH-λEdd grid.
We observed that the soft excess strength rises strongly with
increasing αox and λEdd binning (by a factor of
five), while the hard X-ray spectral shape remains largely unchanged,
consistent with the interpretation that soft excess is primarily
driven by the warm corona rather than reflection. The trends are
weaker with LUV binning and reversed for MBH binning. The analysis of
the optical-UV X-ray SEDs with AGNSED revealed that the warm corona
radius (in units of Rg) generally increases with λEdd and
decreases with MBH, or equivalently the disk-to-warm-corona transition
consistently occurs near ∼1x104K. The hot corona contracts with
λEdd, and the radius remains independent of MBH, aligning
with disk evaporation predictions.
The soft excess is likely warm-corona dominated, with the
disk-to-warm-corona transition potentially linked to hydrogen
ionization instability at ∼1x104K, which is consistent with previous
work utilizing eFEDS-HSC stacked data. Our work highlights the power
of spectral stacking for revealing the AGN disk-corona connection.
Description:
This catalog contains 4159 type 1 active galactic nuclei (AGNs) from
eROSITA All-Sky Survey (eRASS:5) cross-matched with SDSS-IV and GALEX,
providing basic source information such as redshift, X-ray flux from
eRASS1, and UV flux from GALEX. Along with the main catalog, we also
include their stacked optical-UV-X-ray spectral energy distributions
(SEDs) in bins of black hole mass and Eddington ratio, as well as the
energy conversion factor (ECF) table and bolometric correction (BC)
table, both derived from the stacked SEDs.
fits subdirectory contains stacked X-ray spectra and stacked UV SED.
If you use these stacked spectra, we kindly ask you to cite the paper.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
agn1.dat 548 4159 Source catalog
ecftable.dat 622 72 Energy conversion factor table
bctable.dat 86 27 Bolometric correction table
list.dat 146 146 List of fits files
fits/* . 146 Individual spectra
--------------------------------------------------------------------------------
See also:
J/A+A/682/A34 : SRG/eROSITA all-sky survey catalogs (eRASS1) (Merloni+, 2024)
II/335 : Revised catalog of GALEX UV sources (GUVcat_AIS GR6+7)
(Bianchi+ 2017)
II/294 : SDSS Photometric Catalog, Release 7 (Adelman-McCarthy+ 2009)
http://quasar.astro.illinois.edu/paper_data/DR16Q/ : SDSS DR16Q catalog
(Wu & Shen 2022)
https://datalab.noirlab.edu/data/legacy-surveys : DESI Legacy Survey DR10
Byte-by-byte Description of file: agn1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 23 A23 --- IAUName Official IAU name from eRASS1 (IAUName)
25- 56 A32 --- DetUId Detection ID from eRASS1 (DetUId)
58- 63 I6 --- SkyTile Sky tile ID from eRASS1 (SkyTile)
65- 67 I3 --- IdSrc Source ID in each sky tile from eRASS1
(IdSrc)
69- 83 F15.11 deg RAdeg Right ascension (J2000) from eRASS1 (RAEro)
85- 99 F15.11 deg DEdeg Declination (J2000) from eRASS1 (DEEro)
101-108 F8.5 arcsec ePos Positional uncertainty from eRASS1
(PosErrEro)
110-121 E12.6 --- DetLike0 Detection likelihood in 0.2-2.3keV band
(DetLike0)
123-131 F9.5 ct MLcts1 Source net counts in 0.2-2.3keV band
(MLcts1)
133-144 E12.6 mW/m2 MLFlux1 Source flux in 0.2-2.3keV band (MLFlux1)
146-157 E12.6 mW/m2 e_MLFlux1 ?=- 1-sigma uncertainty in MLFlux1
(e_MLFlux1)
159-170 E12.6 mW/m2 MLFluxP4 Source flux in 2.0-5.0keV band (MLFluxP4)
172-183 E12.6 mW/m2 e_MLFluxP4 1-sigma uncertainty in MLFluxP4
(e_MLFluxP4)
185-199 F15.11 deg RALdeg Right ascension (J2000) of the counterpart
from LS10 (RALS10)
201-215 F15.11 deg DELdeg Declination (J2000) of the counterpart
from LS10 (DELS10)
217-228 E12.66 arcsec eLpos Positional uncertainty from LS10:
sqrt(1/RAIVAR+1/DECIVAR) (PosErrLS10)
230-247 A18 --- SDSS Source name from SDSS DR16Q (SDSSName)
249-253 I5 --- Plate Plate ID from SDSS DR16Q (SDSSPlate)
255-259 I5 --- MJD MJD from SDSS DR16Q (SDSSMJD)
261-264 I4 --- Fiber Fiber ID from SDSS DR16Q (SDSSFiberId)
266-271 F6.2 s NUVexp Exposure time for GALEX NUV (NUVexp)
273-281 F9.7 --- z ?=-1 Spectroscopic redshift from
compilation (Salvato+, in prep.) (z)
283-292 F10.7 --- e_z ?=-1 Uncertainty in z (e_z)
294-324 A31 --- r_z References for redshift (1)
326-334 F9.6 [-] logEdd Log Eddington ratio from Wu&Shen22 (logEdd)
336-344 F9.7 [-] e_logEdd Uncertainty in logEdd (e_logEdd)
346-352 F7.4 [Msun] logMBH Log BH mass from Wu & Shen
(2022ApJS..263...42W 2022ApJS..263...42W), prefering Hbeta
otherwise MgII (logMBH)
354-360 F7.5 [Msun] e_logMBH Uncertainty in logMBH (e_logMBH)
362-369 F8.5 [10-7W] logLbol Log bolometric luminosity from Wu & Shen
(2022ApJS..263...42W 2022ApJS..263...42W) (logLbol)
371-378 F8.6 [10-7W] e_logLbol Uncertainty in logLbol (e_logLbol)
380-387 F8.6 --- E(B-V) Galactic extinction E(B-V) reddening from
Schlegel et al. (1998ApJ...500..525S 1998ApJ...500..525S)
(EBV)
389-400 E12.6 cm-2 GalNH Total Galactic absorption column density
(GalNH)
402-413 E12.6 mW/m2/Hz FNUV Observer-frame NUV-band monochromatic flux
in erg/cm^2/s/Hz (FNUV)
415-426 E12.6 mW/m2/Hz e_FNUV 1-sigma uncertainty in FNUV (e_FNUV)
428-439 E12.6 mW/m2/Hz Fu ?=- Observer-frame u-band monochromatic
flux in erg/cm2/s/Hz (Fu)
441-452 E12.6 mW/m2/Hz e_Fu ?=- 1-sigma uncertainty in Fu (e_Fu)
454-465 E12.6 mW/m2/Hz Fg ?=- Observer-frame g-band monochromatic
flux in erg/cm2/s/Hz (Fg)
467-478 E12.6 mW/m2/Hz e_Fg ?=- 1-sigma uncertainty in Fg (e_Fg)
480-491 E12.6 0.1nW/eV L2keV Rest-frame 2keV monochromatic luminosity
in erg/s/keV, corrected for Galactic-NH
(L2keV)
493-504 E12.6 0.1nW/eV e_L2keV 1-sigma uncertainty in L2keV (e_L2keV)
506-517 E12.6 kW/m L2500AA Rest-frame 2500 angstrom monochromatic
luminosity in erg/s/AA, corrected for
Galactic extinction (L2500AA)
519-530 E12.6 kW/m e_L2500AA 1-sigma uncertainty in L2500AA (e_L2500AA)
532-539 F8.6 --- a-ox Slope of line connecting 2500 angstrom and
2keV (stronger X-ray means smaller
alpha_ox) (a-ox)
541-548 F8.6 --- e_a-ox 1-sigma uncertainty in alpha_ox
(e_a-ox) (2)
--------------------------------------------------------------------------------
Note (1): References as follows:
Ahumada2020aa = Ahumada et al., 2020ApJS..249....3A 2020ApJS..249....3A, Cat. V/154
Alam2015aa = Alam et al., 2015ApJS..219...12A 2015ApJS..219...12A, Cat. V/147
DESIDR1DesiCollab2025 = Abdul-Karim et al., 2025arXiv250314745D 2025arXiv250314745D
Drinkwater2010aa = Drinkwater et al., 2010MNRAS.401.1429D 2010MNRAS.401.1429D,
Cat. J/MNRAS/401/1429
QuaiaG20.5Storey-Fisher2024 = Storey-Fisher et al., 2024ApJ...964...69S 2024ApJ...964...69S
SDSSDR17Abdurrouf2022 = Abdurro'uf et al., 2022ApJS..259...35A 2022ApJS..259...35A, Cat. III/286
sdss-v:eFEDSspeczspAll-v604 = Almeida et al., 2023ApJS..267...44A 2023ApJS..267...44A,
Aydar et al., 2025A&A...698A.132A 2025A&A...698A.132A, Cat. J/A+A/698/A132
Note (2): a-ox is related to L2500AA and L2keV via:
a-ox = 0.3838*(log10(L2500AA) - log10(L2keV) + 5.702)
where 5.702 is the conversion factor from erg/s/Å to erg/s/keV.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: ecftable.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 F3.1 [Msun] e_logMBH Lower edge of log BH mass bin
5- 7 F3.1 [Msun] E_logMBH Upper edge of log BH mass bi
9- 13 F5.2 --- e_logEdd [] Lower edge of log Eddington ratio bin
15- 19 F5.2 --- E_logEdd [] Upper edge of log Eddington ratio bin
21- 23 F3.1 --- e_z Lower edge of redshift
25- 27 F3.1 --- E_z Upper edge of redshift
29- 35 A7 --- CRband Observed-frame energy range (keV) from
which to calculate count rate
(CountrateBand)
37- 42 F6.4 --- gamma Photon index in "CRband" band (gamma)
44- 49 F6.4 --- e_gamma Lower error of gamma (16th-50th quantile)
(e_gamma)
51- 56 F6.4 --- E_gamma Upper error of gamma
(50th-84th quantile) (E_gamma)
58- 64 F7.4 mW/m2 logecfEro Log10 energy conversion factor from flux
(erg/cm2/s) to count rate
(logecfEro) (1)
66- 71 F6.4 mW/m2 e_logecfEro Lower error of logecfEro
(16th-50th quantile) (e_logecfEro)
73- 78 F6.4 mW/m2 E_logecfEro Upper error of logecfEro
(50th-84th quantile) (E_logecfEro)
80- 86 F7.4 --- FP00 Rest-frame 0.1-10.0 keV flux to
observed-frame "CRband" band flux ratio
(FP00)
88- 94 F7.4 --- e_FP00 Lower error of FP00 (16th-50th quantile)
(e_FP00)
96-102 F7.4 --- E_FP00 Upper error of FP00 (50th-84th quantile)
(E_FP00)
104-110 F7.4 --- FP01 Rest-frame 0.2-0.5 keV flux to
observed-frame "CRband" band flux ratio
(FP01)
112-118 F7.4 --- e_FP01 Lower error of FP01 (16th-50th quantile)
(e_FP01)
120-126 F7.4 --- E_FP01 Upper error of FP01 (50th-84th quantile)
(E_FP01)
128-134 F7.4 --- FP02 Rest-frame 0.2-2.0 keV flux to
observed-frame "CRband" band flux ratio
(FP02)
136-142 F7.4 --- e_FP02 Lower error of FP02 (16th-50th quantile)
(e_FP02)
144-150 F7.4 --- E_FP02 Upper error of FP02 (50th-84th quantile)
(E_FP02)
152-158 F7.4 --- FP03 Rest-frame 0.2-2.3 keV flux to
observed-frame "CRband" band flux ratio
(FP03)
160-166 F7.4 --- e_FP03 Lower error of FP02 (16th-50th quantile)
(e_FP03)
168-174 F7.4 --- E_FP03 Upper error of FP02 (50th-84th quantile)
(E_FP03)
176-182 F7.4 --- FP04 Rest-frame 0.2-12.0 keV flux to
observed-frame "CRband" band flux ratio
(FP04)
184-190 F7.4 --- e_FP04 Lower error of FP02 (16th-50th quantile)
(e_FP04)
192-198 F7.4 --- E_FP04 Upper error of FP02 (50th-84th quantile)
(E_FP04)
200-205 F6.4 --- FP05 Rest-frame 0.5-1.0 keV flux to
observed-frame "CRband" band flux ratio
(FP05)
207-212 F6.4 --- e_FP05 Lower error of FP02 (16th-50th quantile)
(e_FP05)
214-219 F6.4 --- E_FP05 Upper error of FP02 (50th-84th quantile)
(E_FP05)
221-226 F6.4 --- FP06 Rest-frame 0.5-1.2 keV flux to
observed-frame "CRband" band flux ratio
(FP06)
228-233 F6.4 --- e_FP06 Lower error of FP02 (16th-50th quantile)
(e_FP06)
235-240 F6.4 --- E_FP06 Upper error of FP02 (50th-84th quantile)
(E_FP06)
242-248 F7.4 --- FP07 Rest-frame 0.5-2.0 keV flux to
observed-frame "CRband" band flux ratio
(FP07)
250-255 F6.4 --- e_FP07 Lower error of FP02 (16th-50th quantile)
(e_FP07)
257-262 F6.4 --- E_FP07 Upper error of FP02 (50th-84th quantile)
(E_FP07)
264-270 F7.4 --- FP08 Rest-frame 0.5-4.5 keV flux to
observed-frame "CRband" band flux ratio
(FP08)
272-277 F6.4 --- e_FP08 Lower error of FP02 (16th-50th quantile)
(e_FP08)
279-284 F6.4 --- E_FP08 Upper error of FP02 (50th-84th quantile)
(E_FP08)
286-292 F7.4 --- FP09 Rest-frame 0.5-7.0 keV flux to
observed-frame "CRband" band flux ratio
(FP09)
294-299 F6.4 --- e_FP09 Lower error of FP02 (16th-50th quantile)
(e_FP09)
301-306 F6.4 --- E_FP09 Upper error of FP02 (50th-84th quantile)
(E_FP09)
308-314 F7.4 --- FP10 Rest-frame 1.0 keV monochromatic flux to
observed-frame "CRband" band flux ratio
(FP10)
316-321 F6.4 --- e_FP10 Lower error of FP02 (16th-50th quantile)
(e_FP10)
323-328 F6.4 --- E_FP10 Upper error of FP02 (50th-84th quantile)
(E_FP10)
330-335 F6.4 --- FP11 Rest-frame 1.0 keV monochromatic flux
(soft excess removed) to observed-frame
"CRband" band flux ratio (FP11)
337-342 F6.4 --- E_FP11 Lower error of FP02 (16th-50th quantile)
(e_FP11)
344-349 F6.4 --- e_FP11 Upper error of FP02 (50th-84th quantile)
(E_FP11)
351-356 F6.4 --- FP12 Rest-frame 1.0-2.0 keV flux to
observed-frame "CRband" band flux ratio
(FP12)
358-363 F6.4 --- e_FP12 Lower error of FP02 (16th-50th quantile)
(e_FP12)
365-370 F6.4 --- E_FP12 Upper error of FP02 (50th-84th quantile)
(E_FP12)
372-377 F6.4 --- FP13 Rest-frame 1.2-2.0 keV flux to
observed-frame "CRband" band flux ratio
(FP13)
379-384 F6.4 --- E_FP13 Lower error of FP02 (16th-50th quantile)
(e_FP13)
386-391 F6.4 --- e_FP13 Upper error of FP02 (50th-84th quantile)
(E_FP13)
393-398 F6.4 --- FP14 Rest-frame 2.0-4.5 keV flux to
observed-frame "CRband" band flux ratio
(FP14)
400-405 F6.4 --- e_FP14 Lower error of FP02 (16th-50th quantile)
(e_FP14)
407-412 F6.4 --- E_FP14 Upper error of FP02 (50th-84th quantile)
(E_FP14)
414-419 F6.4 --- FP15 Rest-frame 2.0-5.0 keV flux to
observed-frame "CRband" band flux ratio
(FP15)
421-426 F6.4 --- e_FP15 Lower error of FP02 (16th-50th quantile)
(e_FP15)
428-433 F6.4 --- E_FP15 Upper error of FP02 (50th-84th quantile)
(E_FP15)
435-440 F6.4 --- FP16 Rest-frame 2.0-7.0 keV flux to
observed-frame "CRband" band flux ratio
(FP16)
442-447 F6.4 --- e_FP16 Lower error of FP02 (16th-50th quantile)
(e_FP16)
449-454 F6.4 --- E_FP16 Upper error of FP02 (50th-84th quantile)
(E_FP16)
456-461 F6.4 --- FP17 Rest-frame 2.0-10.0 keV flux to
observed-frame "CRband" band flux ratio
(FP17)
463-468 F6.4 --- e_FP17 Lower error of FP02 (16th-50th quantile)
(e_FP17)
470-475 F6.4 --- E_FP17 Upper error of FP02 (50th-84th quantile)
(E_FP17)
477-482 F6.4 --- FP18 Rest-frame 2.0-12.0 keV flux to
observed-frame "CRband" band flux ratio
(FP18)
484-489 F6.4 --- e_FP18 Lower error of FP02 (16th-50th quantile)
(e_FP18)
491-496 F6.4 --- E_FP18 Upper error of FP02 (50th-84th quantile)
(E_FP18)
498-503 F6.4 --- FP19 Rest-frame 4.0-10.0 keV flux to
observed-frame "CRband" band flux ratio
(FP19)
505-510 F6.4 --- e_FP19 Lower error of FP02 (16th-50th quantile)
(e_FP19)
512-517 F6.4 --- E_FP19 Upper error of FP02 (50th-84th quantile)
(E_FP19)
519-524 F6.4 --- FP20 Rest-frame 4.5-12.0 keV flux to
observed-frame "CRband" band flux ratio
(FP20)
526-531 F6.4 --- e_FP20 Lower error of FP02 (16th-50th quantile)
(e_FP20)
533-538 F6.4 --- E_FP20 Upper error of FP02 (50th-84th quantile)
(E_FP20)
540-545 F6.4 --- FP21 Rest-frame 5.0-8.0 keV flux to
observed-frame "CRband" band flux ratio
(FP21)
547-552 F6.4 --- e_FP21 Lower error of FP02 (16th-50th quantile)
(e_FP21)
554-559 F6.4 --- E_FP21 Upper error of FP02 (50th-84th quantile)
(E_FP21)
561-566 F6.4 --- FP22 Rest-frame 5.1-6.1 keV flux to
observed-frame "CRband" band flux ratio
(FP22)
568-573 F6.4 --- e_FP22 Lower error of FP02 (16th-50th quantile)
(e_FP22)
575-580 F6.4 --- E_FP22 Upper error of FP02 (50th-84th quantile)
(E_FP22)
582-587 F6.4 --- FP23 Rest-frame 6.2-7.1 keV flux to
observed-frame "CRband" band flux ratio
(FP23)
589-594 F6.4 --- e_FP23 Lower error of FP02 (16th-50th quantile)
(e_FP23)
596-601 F6.4 --- E_FP23 Upper error of FP02 (50th-84th quantile)
(E_FP23)
603-608 F6.4 --- FP24 Rest-frame 7.2-8.2 keV flux to
observed-frame "CRband" band flux ratio
(FP24)
610-615 F6.4 --- e_FP24 Lower error of FP02 (16th-50th quantile)
(e_FP24)
617-622 F6.4 --- E_FP24 Upper error of FP02 (50th-84th quantile)
(E_FP24)
--------------------------------------------------------------------------------
Note (1): You can use "logecfEro" to convert count rate (ct/s) in observed-frame
"CRBand" (e.g., 0.2-2.3 keV) to flux (erg/cm2/s) in the same band
(also observed-frame). This assumes eROSITA on-axis response.
For other instruments (e.g., XMM, Chandra), We offer an approximate photon
index "gamma" (NE∼E-gamma) in the "CRBand", which you can feed with
PIMMS to convert your count rate to flux (erg/cm2/s).
After you have the flux (erg/cm2/s) in the observed-frame "CRBand",
you can further convert it to flux (erg/cm2/s) in other bands. Here we
provide 25 bands (broad and narrow). You could use our code for the most
up-to-date ECF calculation: https://github.com/AstroChensj/AGN1ECF
--------------------------------------------------------------------------------
Byte-by-byte Description of file: bctable.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 A9 --- Band Which band to bolometric? (1)
11- 13 F3.1 [Msun] e_logMBH Lower edge of log BH mass bin
15- 17 F3.1 [Msun] E_logMBH Upper edge of log BH mass bin
19- 23 F5.2 --- e_logEdd [] Lower edge of log Eddington ratio bin
25- 29 F5.2 --- E_logEdd [] Upper edge of log Eddington ratio bin
31- 48 F18.14 --- bc Bolometric correction factor (2)
50- 67 F18.15 --- e_bc Lower error of BC (16-50)
69- 86 F18.15 --- E_bc Upper error of BC (50-84)
--------------------------------------------------------------------------------
Note (1): Band≡"B band" means the conversion from 4400 angstrom
luminosity (4400*L4400AA, where L4400AA is monochromatic luminosity
at 4400 angstrom), to bolometric.
Note (2): Bolometric correction factor is defined as, the ratio between
bolometric luminosity (10-5keV to 103keV) and luminosity in
some band, specified by WhichBand.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: list.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 32 A32 --- FileName Name of the fits file in subdirectory fits (1)
35-146 A112 --- Title Title of the file
--------------------------------------------------------------------------------
Note (1):
Naming convention for the stacked X-ray spectra: ABC_D.fits
1. A: src = source PI spectrum
bkg = background PI spectrum
rmf = response matrix file
arf = ancillary response file
fene = first contributing energy for each source
2. B: c038 = eSASS processing number
3. C: bhmass = BH-mass sample consisting of 4159 sources in total
specz = spec-z sample consisting of 17929 sources in total
4. D: for 0d binning: _D is left blank
for 1d binning: D is the physical binning name, followed by the
subgroup index in that binning. The physical binning name can be
aox = luv, edd, mbh`. The sample is always separated into
3 nearly equally populated subgroups, so index=0,1,2, with 0
corresponding to the lowest value. Example: aox0, edd1
for 2d binning: `D` is the combination of two units,
i.e., mbh0edd0, mbh0edd1, ..., mbh2edd2.
Naming convention for the stacked UV SED: `ABUVCD.fits`
1. A: src = source PI spectrum
bkg = background PI spectrum
rmf = response matrix file
arf = ancillary response file
2. B: c038 = eSASS processing number
3. C: bhmass = BH-mass sample consisting of 4159 sources in total
4. D: the combination of two units,
i.e., mbh0edd0, mbh0edd1, ..., mbh2edd2.
How to load the spectra in XSPEC
-------------------------------------------------
For 0d/1d binning, or 2d binning without UV:
-------------------------------------------------
shell
XSPEC12>data srcc038bhmass_edd0.fits
1 spectrum in use
Spectral Data File: srcc038bhmass_edd0.fits Spectrum 1
Net count rate (cts/s) for Spectrum:1 1.143e-01 ± 3.638e-04 (84.5 % total)
Assigned to Data Group 1 and Plot Group 1
Noticed Channels: 1-1024
Telescope: STACKED Instrument: STACKED Channel Type: PI
Exposure Time: 1.024e+06 sec
Using fit statistic: chi
Using Background File bkgc038bhmass_edd0.fits
Background Exposure Time: 1.024e+06 sec
Using Response (RMF) File rmfc038bhmass_edd0.fits for Source 1
Using Auxiliary Response (ARF) File arfc038bhmass_edd0.fits
-------------------------------------------------
For 2d binning with UV:
-------------------------------------------------
shell
XSPEC12>data 1:1 srcc038bhmass_mbh0edd0.fits 1:2
srcc038UVbhmassmbh0edd0.fits
Spectrum #: 1 replaced
2 spectra in use
Spectral Data File: srcc038bhmass_mbh0edd0.fits Spectrum 1
Net count rate (cts/s) for Spectrum:1 1.514e-01 ± 1.669e-03 (86.5 % total)
Assigned to Data Group 1 and Plot Group 1
Noticed Channels: 1-1024
Telescope: STACKED Instrument: STACKED Channel Type: PI
Exposure Time: 6.296e+04 sec
Using fit statistic: chi
Using Background File bkgc038bhmass_mbh0edd0.fits
Background Exposure Time: 6.296e+04 sec
Using Response (RMF) File rmfc038bhmass_mbh0edd0.fits for Source 1
Using Auxiliary Response (ARF) File arfc038bhmass_mbh0edd0.fits
Spectral Data File: srcc038UVbhmassmbh0edd0.fits Spectrum 2
Net count rate (cts/s) for Spectrum:2 1.226e+01±5.183e-01 (100.0% total)
Assigned to Data Group 1 and Plot Group 2
Noticed Channels: 1-3
Telescope: STACKED UV Instrument: STACKED UV Channel Type: PI
Exposure Time: 6.296e+04 sec
Using fit statistic: chi
Using Background File bkgc038UVbhmassmbh0edd0.fits
Background Exposure Time: 6.296e+04 sec
Using Response (RMF) File rmfc038UVbhmassmbh0edd0.fits for Source 1
Using Auxiliary Response (ARF) File arfc038UVbhmassmbh0edd0.fits
--------------------------------------------------------------------------------
History:
From electronic version of the journal
Acknowledgements:
This work is based on data from eROSITA, the soft X-ray instrument
aboard SRG, a joint Russian-German science mission supported by the
Russian Space Agency (Roskosmos), in the interests of the Russian
Academy of Sciences represented by its Space Research Institute (IKI),
and the Deutsches Zentrum fur Luft- und Raumfahrt (DLR). The SRG
spacecraft was built by Lavochkin Association (NPOL) and its
subcontractors, and is operated by NPOL with support from the Max
Planck Institute for Extraterrestrial Physics (MPE). The development
and construction of the eROSITA X-ray instrument was led by MPE, with
contributions from the Dr. Karl Remeis Observatory Bamberg & ECAP (FAU
Erlangen-Nuernberg), the University of Hamburg Observatory, the
Leibniz Institute for Astrophysics Potsdam (AIP), and the Institute
for Astronomy and Astrophysics of the University of Tubingen, with the
support of DLR and the Max Planck Society. The Argelander Institute
for Astronomy of the University of Bonn and the Ludwig Maximilians
Universitat Munich also participated in the science preparation for
eROSITA. The eROSITA data shown here were processed using the eSASS
software system developed by the German eROSITA consortium.
References:
Spectroscopic redshift:
Drinkwater et al., 2010MNRAS.401.1429D 2010MNRAS.401.1429D, Cat. J/MNRAS/401/1429
Alam et al., 2015ApJS..219...12A 2015ApJS..219...12A, Cat. V/147
Ahumada et al., 2020ApJS..249....3A 2020ApJS..249....3A, Cat. V/154
Abdurro'uf et al., 2022ApJS..259...35A 2022ApJS..259...35A, Cat. III/286
Almeida et al., 2023ApJS..267...44A 2023ApJS..267...44A,
Storey-Fisher et al., 2024ApJ...964...69S 2024ApJ...964...69S
Aydar et al., 2025A&A...698A.132A 2025A&A...698A.132A, Cat. J/A+A/698/A132
DESI Collaboration, Abdul-Karim et al., 2025arXiv250314745D 2025arXiv250314745D
Salvato et al., submitted
GALEX photometry:
Bianchi et al., 2017ApJS..230...24B 2017ApJS..230...24B, Cat. II/335
DESI LS10 photometry:
Dey et al., 2019AJ....157..168D 2019AJ....157..168D
Wu et al., 2022ApJS..263...42W 2022ApJS..263...42W,
http://quasar.astro.illinois.edu/paper_data/DR16Q/
eROSITA catalog:
Merloni et al., 2024A&A...682A..34M 2024A&A...682A..34M, Cat. J/A+A/682/34
https://github.com/AstroChensj/Xstack : X-ray spectral stacking code
https://github.com/AstroChensj/AGN1ECF : versatile ECF calculator
(End) Patricia Vannier [CDS] 13-Aug-2025