J/ApJS/177/39 Survey of low-redshift OVI absorbers (Tripp+, 2008)
A high-resolution survey of low-redshift QSO absorption lines: statistics and
physical conditions of O VI absorbers.
Tripp T.M., Sembach K.R., Bowen D.V., Savage B.D., Jenkins E.B., Lehner N.,
Richter P.
<Astrophys. J. Suppl. Ser., 177, 39-102 (2008)>
=2008ApJS..177...39T 2008ApJS..177...39T
ADC_Keywords: Spectra, ultraviolet ; Redshifts ; QSOs ; Spectroscopy
Keywords: cosmology: observations - intergalactic medium
quasars: absorption lines
Abstract:
Using high-resolution ultraviolet spectra of 16 low-z QSOs obtained
with the E140M echelle mode of the Space Telescope Imaging
Spectrograph, we study the physical conditions and statistics of OVI
absorption in the intergalactic medium (IGM) at z<0.5. We identify 51
intervening (zabs<zQSO) OVI systems comprising 77 individual
components, and we find 14 "proximate" systems (zabs∼zQSO)
containing 34 components. For intervening systems (components) with
rest-frame equivalent width Wr>30mÅ, the number of OVI absorbers
per unit redshift dN/dz=15.6+2.9-2.4(21.0+3.2-2.8), and this
decreases to dN/dz=0.9+1.0-0.5(0.3+0.7-0.3) for Wr>300mÅ.
The number per redshift increases steeply as zabs approaches zQSO;
we find that dN/dz is ∼3-10 times higher within 2500km/s of zQSO.
The most striking difference between intervening and proximate systems
is that some proximate absorbers have substantially lower HI/OVI
ratios.
Description:
Our survey of low-redshift OVI absorbers is based primarily on
high-resolution ultraviolet (UV) spectroscopy of QSOs acquired with
the E140M echelle mode of STIS (from 1999 January to 2003 May).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 52 16 QSO's list
table2.dat 114 179 OVI absorbers: integrated total equivalent
widths and column densities
table3.dat 204 245 Profile-fitting parameters for intervening and
proximate OVI absorbers
table7.dat 73 38 *Column density ratios and temperature
constraints of well-aligned components in
intervening OVI absorbers
notes.dat 79 65 Notes from table 2
appendix.dat 80 490 Appendix: comments on line identification,
blending, hot pixel contamination, and
saturation in individual systems
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Note on table7.dat: This table lists data for components with OVI and HI
components that have aligned centroids (see section 2.3.2).
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See also:
VII/23 : Absorption Lines in QSO Spectra (Ellis+ 1978)
J/ApJS/77/203 : QSO absorption systems (Junkkarinen+ 1991)
J/AJ/112/62 : Quasar absorption-line systems (Tanner+ 1996)
J/ApJS/122/355 : Properties of low z QSO absorption systems (Vanden Berk+ 1999)
J/ApJ/599/116 : UV properties of absorbed quasars (Vestergaard+, 2003)
Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 12 A12 --- QSO QSO name
17- 18 I2 h RAh Right ascension (J2000)
20- 21 I2 min RAm Right ascension (J2000)
23- 26 F4.1 s RAs Right ascension (J2000)
28 A1 --- DE- Declination sign (J2000)
29- 30 I2 deg DEd Declination (J2000)
32- 33 I2 arcmin DEm Declination (J2000)
35- 36 I2 arcsec DEs Declination (J2000)
39- 52 A14 --- Name QSO JHHMM+DDMM name
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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- 12 A12 --- QSO Target QSO name
14- 20 F7.5 --- zabs Absorber systemic redshift (1)
22- 33 A12 --- Ion Species and transition used to measure EWr & logN
34- 36 A3 --- n_Ion [eghjkmo, ] Note(s) on species in notes.dat file
38 A1 --- l_EWr [∼ ] Limit flag on EWr
39- 44 F6.1 0.1pm EWr ?=- Rest-frame integrated equivalent width
46- 49 F4.1 0.1pm e_EWr ? Error on EWr
50 A1 --- n_EWr [xfil] Note on EWr in notes.dat file
52- 53 A2 --- l_logN [≥∼ ] Limit flag on logN
54- 58 F5.2 [-] logN ?=- Directly integrated apparent column density
60- 63 F4.2 [-] E_logN ? Positive error on logN
65- 68 F4.2 [-] e_logN ? Negative error on logN
69 A1 --- n_logN [abdikfln] Note on logN in notes.dat file
71- 74 I4 km/s Vel1 ?=- Velocity centroid of component 1 (2)
76- 79 I4 km/s Vel2 ? Velocity centroid of component 2 (2)
81- 83 I3 km/s Vel3 ? Velocity centroid of component 3 (2)
85- 87 I3 km/s Vel4 ? Velocity centroid of component 4 (2)
89- 91 I3 km/s Vel5 ? Velocity centroid of component 5 (2)
93- 95 I3 km/s Vel6 ? Velocity centroid of component 6 (2)
97- 99 I3 km/s Vel7 ? Velocity centroid of component 7 (2)
101-103 I3 km/s Vel8 ? Velocity centroid of component 8 (2)
105-107 I3 km/s Vel9 ? Velocity centroid of component 9 (2)
109 A1 --- n_Vel1 [c] Note on component velocity (3)
111-114 A4 --- Spec Spectrograph used for the measurement
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Note (1): Which in this paper is defined by the centroid of the strongest
component detected in the OVI profiles.
Note (2): Derived from Voigt-profile fitting (see Table 3).
Note (3): 'c' for an optically thick Lyman limit absorber: all available
Lyman series lines are strongly saturated and, consequently, cannot be
used to derive reliable constraints on the HI component structure.
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 12 A12 --- QSO Target QSO name
14- 20 F7.5 --- zabs Absorber systemic redshift (1)
22- 37 A16 --- Class Classification (2)
39- 41 A3 --- Ion Species
43-146 A104 --- line Fitted lines
148-151 I4 km/s Vel ?=- Velocity centroid (3)
153-154 I2 km/s e_Vel ? Error on Vel
155 A1 --- u_Vel Uncertainty flag on Vel (3)
157-159 I3 km/s b ?=- Doppler parameter (3)
161-162 I2 km/s E_b ? Positive error on b
164-165 I2 km/s e_b ? Negative error on b
166 A1 --- u_b Uncertainty flag on b (3)
168-169 A2 --- l_logN [≳ ] Limit flag on logN
170-174 F5.2 [cm-2] logN ?=- Column density of individual components (4)
176-179 F4.2 [cm-2] e_logN ? Error on logN
180 A1 --- u_logN Uncertainty flag on logN (3)
182-201 A20 --- Type Component number (type) (5)
203-204 I2 --- Note ? See comments in "appendix.dat" file
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Note (1): In this paper, we use the centroid of the strongest OVI component
to define the systemic redshift of the absorber.
Note (2): Absorber classification:
(Prox) = absorption systems detected within 5000km/s of the QSO redshift
(Proximate absorbers)
(Int) = systems that are displaced by more than 5000km/s from zQSO
(Intervening systems).
simple = systems in which all HI and OVI components are aligned (see
section 2.3.2)
complex = absorbers that show significant velocity offsets between
HI and OVI components.
Note (3): For each component, we list the velocity centroid (Vel), Doppler
parameter (b), and column density (N) obtained from Voigt-profile
fitting using the software of Fitzpatrick & Spitzer
(1997ApJ...475..623F 1997ApJ...475..623F). The listed parameter uncertainties primarily
reflect the random noise in the measurements. In some cases,
systematic uncertainties due to effects such as line saturation and
blending can be larger than the formal uncertainties listed in the
table. For these more uncertain measurements, we list the formal error
bars indicated by the fitting, but we flag the measurements with a
colon. Comments on the source of the additional systematic
uncertainties are presented in the Appendix.
Note (4): Column densities of individual components detected in each OVI
absorption system (some OVI absorbers show only one component, but
many of the systems have multiple components).
Note (5): For convenience, we number the components in each absorption
system, and we indicate whether the OVI and HI components are aligned
or offset from each other. If the components are aligned, we give the
HI and OVI components the same number, and if a component is offset,
it is given a unique number. For example, in the 3C 249.1 system at
zabs=0.24676, we identify two HI components at v=-79±3km/s
(component 1) and v=0±1km/s (component 2), and we find one OVI
component at v=0±3km/s. The OVI component is aligned with HI
component 2, and thus, the OVI component is also identified as
component 2. By using the same component numbers for aligned HI and
OVI cases, the reader can easily identify which components are matched
together from Table 3.
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Byte-by-byte Description of file: table7.dat
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Bytes Format Units Label Explanations
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1- 12 A12 --- QSO Target QSO name
14- 20 F7.5 --- zabs Absorption system redshift
22- 24 I3 km/s Vel Velocity of the particular component (1)
26 A1 --- l_logTb Limit flag on logTb
27- 30 F4.2 [K] logTb Temperature upper limit, OVI only (2)
32 A1 --- l_logT Limit flag on logT
33- 36 F4.2 [K] logT 3σ upper limit on T, OVI only (3)
38- 41 F4.2 [K] logTb2 ?=- Best measurement of the gas temperature,
HI+OVI (4)
43 A1 --- l_logT2 Limit flag on logT2
44- 47 F4.2 [K] logT2 ?=- 3σ upper limit on the temperature,
HI+OVI (5)
49- 50 I2 km/s b ? Nonthermal broadening component corresponding
to logTb2
52- 56 F5.2 [-] logN(H/O) Log of the HI/OVI column-density ratio
58 A1 --- l_logN(C/O) Limit flag on logNC/O
59- 63 F5.2 [-] logN(C/O) ?=- Log of the CIII/OVI column-density ratio
65- 73 A9 --- Class Absorber classification (6)
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Note (1): From which the temperature and columns density ratios were measured.
Note (2): Implied by the best-fit OVI b-value (eq. [7]:
T=mb2/2k=A(b/0.129)2 where A is the atomic mass number and the
numerical coefficient assumes that b is in km/s and T is in Kelvin).
Note (3): Indicating by propagating the uncertainty in b(OVI) through eq. (7).
Note (4): Found by solving eq. (8) using the OVI and HI b-values (logT, with T
measured in degrees kelvin).
Note (5): Found by propagating the b-value uncertainties through eq. (8):
b2=0.1292x(T/A)+b2nt where bnt is a nonthermal broadening
term.
Note (6): Absorber classification:
Complex = systems that show significant velocity offsets between
low-ionization and high-ionization line
Simple = absorbers that are entirely composed of aligned HI and OVI
components
Simple* = indicate that the majority of the OVI and HI profiles are
well aligned and can be analyzed as a single-phase system
Uncertain = in some instances, the HI profiles and component centroids
are poorly constrained, e.g., if the absorber is a black
Lyman-limit system presenting only badly saturated Lyman
series lines or if HI is not detected at all (as found in
several systems near the QSO redshifts); in these cases,
we list the classification as uncertain.
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Byte-by-byte Description of file: notes.dat
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Bytes Format Units Label Explanations
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1 A1 --- Note Note designation
3- 79 A77 --- Text Text of note
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Byte-by-byte Description of file: appendix.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- Note Note number
4- 80 A77 --- Text Text of note
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Nomenclature note :
<[TSB2008] QSO JHHMM+DDMM abs N.NNNNN> in Simbad.
History:
From electronic version of the journal
(End) Emmanuelle Perret [CDS] 24-Sep-2009