J/ApJ/871/35 HST/COS spectra of QSOs with SiIV data (Zheng+, 2019)
Revealing the Milky Way's hidden circumgalactic medium with the Cosmic Origins
Spectrograph Quasar Database for Galactic Absorption Lines.
Zheng Y., Peek J.E.G., Putman M.E., Werk J.K.
<Astrophys. J., 871, 35 (2019)>
=2019ApJ...871...35Z 2019ApJ...871...35Z
ADC_Keywords: Active gal. nuclei; QSOs; Spectra, ultraviolet; Redshifts
Keywords: Galaxy: halo ; Galaxy: structure ; quasars: absorption lines ;
techniques: spectroscopic
Abstract:
Every quasar (quasi-stellar object; QSO) spectrum contains
absorption-line signatures from the interstellar medium, disk-halo
interface, and circumgalactic medium (CGM) of the Milky Way (MW). We
analyze Hubble Space Telescope/Cosmic Origins Spectrograph (COS)
spectra of 132 QSOs to study the significance and origin of SiIV
absorption at |vLSR|≤100km/s in the Galactic halo. The gas in the
north predominantly falls in at -50≲vLSR≲0km/s, whereas in the
south, no such pattern is observed. The SiIV column density has an
average and a standard deviation of <NSiIV≥(3.8±1.4)x1013cm-2.
At |b|≳30°, NSiIV does not significantly correlate with b,
which cannot be explained by a commonly adopted flat-slab geometry. We
propose a two-component model to reconstruct the NSiIV-b
distribution: a plane-parallel component NDH⊥ to account for
the MW's disk-halo interface and a global component NG to reproduce
the weak dependence on b. We find
NDH⊥=1.3-0.7+4.7x1012cm-2 and
NG=3.4±0.3)x1013cm-2 on the basis of Bayesian analyses and
block bootstrapping. The global component is most likely to have a
Galactic origin, although its exact location is uncertain. If it were
associated with the MW's CGM, we would find
Mgas,all≳
4.7x109M☉(Cf/1)(R/75kpc)2(fSiIV/0.3)-1(Z/0.3Z☉)-1
for the cool gas at all velocities in the Galactic halo. Our analyses
show that there is likely a considerable amount of gas at
|vLSR|≤100km/s hidden in the MW's CGM.
Description:
We obtain our QSO spectra from the Hubble Space Telescope (HST)
Spectroscopic Legacy Archive (HSLA; Peeples+ 2017cos..rept....4P).
In this work, we focus on the QSOs, AGNs, and Seyferts categories,
which we will henceforth refer to as the HSLA QSO catalog.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 223 132 Si IV data sample
sp/* . 135 HST COS individual 2D spectra (continuum
normalized lines) in FITS format
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Description of file:
Zheng18_Table1.fits available in the FTP section, is the original table
in FITS format downloaded from http://github.com/yzhenggit/Zheng18_MWCGM/
See also:
B/hst : HST Archived Exposures Catalog (STScI, 2007)
J/ApJS/97/1 : HST Quasar Absorption Line Key Project. X. (Lockman+ 1995)
J/ApJS/122/355 : Low z QSO absorption systems (Vanden Berk+, 1999)
J/ApJ/729/87 : SiIV absorption systems (Cooksey+, 2011)
J/ApJ/736/42 : HST QSO Catalog (Ribaudo+, 2011)
J/ApJ/804/79 : HST/COS obs. of QSOs within 600kpc of M31 (Lehner+, 2015)
J/ApJ/818/113 : HST observations of QSOs with medium spectra (Neeleman+, 2016)
J/ApJS/230/6 : HST/COS & /STIS absorption-line spectrosc. II. (Keeney+, 2017)
J/ApJS/243/2 : SiIV and NV absorption line SDSS quasar systems (Chen+, 2019)
https://media.stsci.edu/hlsp/cos-gal : the COS Quasar Database for Galactic
Absorption Lines (COS-GAL) on MAST
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- Seq [1/132] Running sequence number
5- 28 A24 --- ID HSLA-V1 identifier (1)
30- 40 A11 --- Grism1 Grism(s) used for the HST/COS spectrum;
column added by CDS
42- 46 A5 --- Grism2 Grism used for the second HST/COS spectrum
if any; column added by CDS
48- 55 F8.4 deg GLON SIMBAD Galactic longitude
57- 64 F8.4 deg GLAT [-83.7/82.1] SIMBAD Galactic latitude
66- 73 F8.4 deg RAdeg Rigth ascension (ICRS)
75- 82 F8.4 deg DEdeg Declination (ICRS)
84- 89 F6.4 --- z [0.002/3]? SIMBAD redshift
91- 95 F5.1 --- SNRSiIV [12.5/154.2] S/N per resolution element for
the absorption-free region between
1394Å and 1401Å (2)
97- 98 I2 --- Q [-1/1] Quality flag (3)
100-105 F6.3 --- logN1393 [13.2/14.3] Log of apparent column density for
SiIV 1393Å integrated from -100 to 100km/s
107-111 F5.3 --- e_logN1393 [0.002/0.07] logN1393 uncertainty
113-121 E9.4 cm-2 N1393 Apparent column density for SiIV 1393Å
integrated from -100 to 100km/s
123-131 E9.4 cm-2 e_N1393 N1393 uncertainty
133-137 F5.1 km/s V1393 [-51.4/40.1] Centroid velocity for
SiIV 1393Å integrated from -100 to 100km/s
139-143 F5.1 km/s e_V1393 [0.3/9]? V1393 uncertainty
145-150 F6.3 --- logN1402 [13.2/14.1] Log of apparent column density for
SiIV 1402Å integrated from -100 to 100km/s
152-156 F5.3 --- e_logN1402 [0.003/0.2] logN1402 uncertainty
158-166 E9.4 cm-2 N1402 Apparent column density for SiIV 1402Å
integrated from -100 to 100km/s
168-176 E9.4 cm-2 e_N1402 N1402 uncertainty
178-182 F5.1 km/s V1402 [-50.5/42.7] Centroid velocity for
SiIV 1402Å integrated from -100 to 100km/s
184-188 F5.1 km/s e_V1402 [0.5/17]? V1402 uncertainty
190-223 A34 --- OName SIMBAD name
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Note (1): QSO ID as adopted by HSLA first data release
(Peeples+ 2017cos..rept....4P).
Note (2): The S/N value can be calculated as S/N per pix xN/N0.5, where N
is the total number of pixels for a corresponding resolution.
For G130M grating, N=6.
Note (3): Quality flag (see Section 2.2) as follows:
0 = this target has spectrally resolved doublet profiles,
19 = SiIV lines are saturated (11 occurrences),
-1 = 1393Å line is abnormally stronger than 1402Å (2 occurrences).
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History:
Downloaded from http://github.com/yzhenggit/Zheng18_MWCGM/
(End) Emmanuelle Perret [CDS] 27-Jul-2020