J/ApJ/710/613 Broad HI absorbers (Danforth+, 2010)
Broad H I absorbers as metallicity-independent tracers of the warm-hot
intergalactic medium.
Danforth C.W., Stocke J.T., Shull J.M.
<Astrophys. J., 710, 613-633 (2010)>
=2010ApJ...710..613D 2010ApJ...710..613D (SIMBAD/NED BibCode)
ADC_Keywords: Active gal. nuclei ; H I data ; Spectroscopy ; Ultraviolet ; QSOs
Keywords: cosmological parameters - cosmology: observations -
intergalactic medium - quasars: absorption lines -
ultraviolet: general
Abstract:
We compile a catalog of reliable BLA (thermally broadened Lyα
absorber) candidates along seven active galactic nucleus sight lines
from a larger set of Lyα absorbers observed by the Space
Telescope Imaging Spectrograph on the Hubble Space Telescope (HST). We
compare our measurements based on independent reduction and analysis
of the data to those published by other research groups. We examine
the detailed structure of each absorber and determine a reliable line
width and column density. Purported BLAs are grouped into probable
(15), possible (48), and non-BLA (56) categories. Based on 164
measured curve of growth (COG) HI line measurements, we statistically
correct the observed line widths via a Monte Carlo simulation.
Finally, we present new, high signal-to-noise ratio observations of
several of the BLA candidate lines from Early Release Observations
made by the Cosmic Origins Spectrograph on HST.
Description:
Until the recent installation of the Cosmic Origins Spectrograph
(COS), the best data for a BLA search come from recent STIS echelle
spectroscopy, which typically features the highest S/N combined with a
spectral resolution sufficient to resolve HI lines of widths less
than ∼30km/s. Lehner et al. (2007ApJ...658..680L 2007ApJ...658..680L) produced a
large compilation of seven AGN sight lines and ∼100 candidate BLAs
based on b-values≥40km/s.
Late in the analysis process, we obtained observations of
PKS 0405-123 by the HST/COS (J. Green et al. 2012ApJ...744...60G 2012ApJ...744...60G;
S. Osterman et al. 2010arXiv1012.5811O 2010arXiv1012.5811O) as part of its public Early
Release Observations (ERO) program. These data were obtained in the
G130M grating (1132Å<λ<1468Å) with a nominal resolution
R∼20000 (Δv=15km/s).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 131 7 Broad Lymanα (BLA) sample sight lines
table2.dat 166 119 Probable, possible, and non-BLA absorbers
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See also:
J/ApJS/182/378 : HI and OVI absorbers in nearby Universe (Wakker+, 2009)
J/ApJ/701/1219 : Galaxy survey in 3 QSO fields (Chen+, 2009)
J/ApJ/679/194 : Low-z intergalactic medium. III. (Danforth+, 2008)
J/ApJ/636/631 : Lyman-alpha forest toward PKS 0405-123 (Williger+, 2006)
J/ApJS/164/1 : IGM absorbers toward HE 0226-4110 (Lehner+, 2006)
J/ApJ/643/680 : Imaging and spectroscopy around PKS 0405-123 (Prochaska+,
2006)
J/ApJS/155/351 : Absorption toward PG 1116+215 (Sembach+, 2004)
J/ApJ/617/718 : Atomic data and EW for PKS 0405-123 (Prochaska+, 2004)
J/ApJ/524/536 : Nearby Lyα quasar absorbers (Impey+, 1999)
J/ApJ/508/200 : QSO low-z Lyα absorbers (Tripp+, 1998)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 12 A12 --- AGN Sight line
14- 15 I2 h RAh Hour of right ascension (J2000)
17- 18 I2 min RAm Minute of right ascension (J2000)
20- 23 F4.1 s RAs Second of right ascension (J2000)
25 A1 --- DE- Sign of declination (J2000)
26- 27 I2 deg DEd Degree of declination (J2000)
29- 30 I2 arcmin DEm Arcminute of declination (J2000)
32- 33 I2 arcsec DEs Arcsecond of declination (J2000)
35- 39 F5.3 --- zAGN AGN redshift
41- 45 F5.3 --- Delz Maximum absorption path length (Δzmax)
47- 51 F5.3 --- DelX Cosmologically corrected maximum path length
(ΔXmax)
53-131 A79 --- Ref Reference (1)
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Note (1): Most recent detailed STIS/E140M analysis; all are also included in
Lehner et al. (2007ApJ...658..680L 2007ApJ...658..680L) and Danforth & Shull (2008,
Cat. J/ApJ/679/194).
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 2 A2 --- Abs Probable, Possible or Non-absorber category (1)
4- 15 A12 --- AGN Sight line
17- 23 F7.5 --- zabs Absorption redshift
25- 27 I3 km/s b1 ? Line width of component 1 (2)
28 A1 --- u_b1 [:] Uncertainty flag on b1
30- 31 I2 km/s E_b1 ? Positive error on b1
33- 34 I2 km/s e_b1 ? Negative error on b1
36- 37 I2 km/s b1d ? Second b1 value
39- 41 A3 --- n_b1 [COG/Nd/Nm ] Note on b1 (3)
43- 47 F5.2 [cm-2] logN1 ? Log of HI column density of component 1
48 A1 --- u_logN1 [?:] Uncertainty flag on logN1
50- 53 F4.2 [cm-2] E_logN1 ? Positive error on logN1
55- 58 F4.2 [cm-2] e_logN1 ? Negative error on logN1
59- 60 A2 --- n_logN1 [Nd/Nm] Not detected or Not measured (3)
62- 64 A3 --- Ref Reference (4)
66- 68 I3 km/s b2 ? Line width of component 2 (2)
69 A1 --- u_b2 [:] Uncertainty flag on b2
71- 72 I2 km/s E_b2 ? Positive error on b2
74- 75 I2 km/s e_b2 ? Negative error on b2
77- 78 I2 km/s b2d ? Second b2 value
80- 82 A3 --- n_b2 [COG/Nd/Nm/bl ] Note on b2 (3)
84 A1 --- l_logN2 Limit flag on logN2
85- 89 F5.2 [cm-2] logN2 ? Log of HI column density of component 2
91- 94 F4.2 [cm-2] E_logN2 ? Positive error on logN2
96- 99 F4.2 [cm-2] e_logN2 ? Negative error on logN2
101-102 A2 --- n_logN2 [Nd/Nm] Not detected or Not measured (3)
104-107 A4 --- Ref2 Reference (4)
109-111 I3 km/s b0 ? Mean line width (2)
112 A1 --- u_b0 [:] Uncertainty flag on b0
114-115 I2 km/s b0d ? Second b0 value
117-119 A3 --- n_b0 [COG/LW* ] Note on b0 (3)
121-125 F5.2 [cm-2] logN0 ? Log of mean Hydrogen column density
126-127 A2 --- n_logN0 [Nd] Nd: Non detected (3)
129-166 A38 --- Notes Absorber notes
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Note (1): Category as follows:
Pr = Probable BLA. There is no definitive test for BLAs, but we classify as
"probable" any system with well-defined bCOG≥40km/s or bLW>60km/s
("LW" for Lyα line width; "COG" for curve of growth) confirmed
by independent measurement of Lehner et al. (2007ApJ...658..680L 2007ApJ...658..680L) and
ourselves and with no obvious sign of multiple component structure
(such as an asymmetric profile) in Lyα or higher Lyman lines or
metal ions (if available). Fifteen systems fall within this category.
Note that we do not a priori use the presence or absence of OVI, NV,
or other warm-hot intergalactic medium (WHIM) sign posts as a BLA
determinant, although several OVI detections are present in this
sample.
Po = Possible BLA. Less likely than category A, the "possible" category
includes systems with 40km/s≤bLW≤60km/s. This category also holds
intermediate cases, where an absorber shows ambiguous component
structure or a high degree of uncertainty as to line width and/or
continuum fit, but a broad HI system component cannot be reasonably
ruled out. Forty-eight HI absorbers fall in this category.
No = Non-BLA. Nearly half (56/119) of the HI lines with b≥40km/s published
by Lehner et al. (2007ApJ...658..680L 2007ApJ...658..680L) or Danforth & Shull (2008,
Cat. J/ApJ/679/194) are most likely not BLAs by our assessment for a
variety of reasons: measured bCOG<40km/s or bLW<40km/s; probable
alternate line identification; obvious narrow component structure; or
simply not detected as absorption features in our reduction of the
data.
Note (2): Line width is usually denoted in terms of the corresponding Doppler
parameter b∼FWHM/2(ln2)0.5~(2σ)0.5 where σ is the
Gaussian width. See section 1 for further details.
Note (3): Flag as follows:
Nd = Non detected
Nm = Non measured
LW = Lyα line width
COG = curve of growth
Note (4): Measurement sources as follows:
L07 = Lehner et al. 2007ApJ...658..680L 2007ApJ...658..680L (and sources therein);
DS08 = Danforth & Shull 2008, Cat. J/ApJ/679/194;
W06 = Williger et al. 2006, Cat. J/ApJ/636/631;
S05 = Savage et al. 2005ApJ...626..776S 2005ApJ...626..776S;
S04 = Sembach et al. 2004, Cat. J/ApJS/155/351;
R04 = Richter et al. 2004ApJS..153..165R 2004ApJS..153..165R;
This = this work.
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History:
* 13-Mar-2012: From electronic version of the journal
* 29-Apr-2012: "PG 0953+414" converted into "PG 0953+415" in table1,
to be in coherence with the table2. Both names are found in the
literature but refer to the same AGN.
(End) Emmanuelle Perret [CDS] 13-Mar-2012