J/ApJ/508/200 QSO low-z Lyα absorbers (Tripp+, 1998)
The relationship between galaxies and low-redshift weak Lyα absorbers in
the directions of H1821+643 and PG 1116+215.
Tripp T.M., Lu L., Savage B.D.
<Astrophys. J. 508, 200 (1998)>
=1998ApJ...508..200T 1998ApJ...508..200T
ADC_Keywords: QSOs ; Redshifts ; Equivalent widths
Keywords: galaxies: distances and redshifts - quasars: absorption lines -
quasars: individual (H1821+643, PG 1116+215)
Abstract:
To study the nature of low-z Lyα absorbers in the spectra of
QSOs, we have obtained high signal-to-noise ratio (S/N) UV spectra
of H1821+643 (zem=0.297) and PG 1116+215 (zem=0.177) with the
Goddard High-Resolution Spectrograph on the Hubble Space Telescope.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 57 154 Redshifts of galaxies in the field of H1821+643
table2.dat 57 118 Redshifts of galaxies in the field of PG 1116+215
table4.dat 67 54 Absorption lines detected in the GHRS G140L
spectrum of H1821+643
table5.dat 61 31 Absorption lines detected in the GHRS G140L
spectrum of PG 1116+215
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Byte-by-byte Description of file: table1.dat table2.dat
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Bytes Format Units Label Explanations
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1- 3 A3 --- Ref Origin of redshifts (1)
5- 6 I2 h RAh Right ascension (J2000)
8- 9 I2 min RAm Right ascension (J2000)
11- 15 F5.2 s RAs Right ascension (J2000)
17 A1 --- DE- Declination sign (J2000)
18- 19 I2 deg DEd Declination (J2000)
21- 22 I2 arcmin DEm Declination (J2000)
24- 27 F4.1 arcsec DEs Declination (J2000)
29- 35 F7.5 --- z Weighted mean redshift (2)
37- 39 I3 km/s e_z ? Weighted uncertainty on redshift (2)
41- 44 F4.1 mag Bmag ? POSS II BJ magnitude (3)
46- 50 F5.1 mag BMAG ? Absolute B magnitude (4)
52- 56 F5.3 Mpc rho ? Projected distance to sight line (5)
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Note (1): Only in table1:
T98: Redshifts from Tripp et al., 1998, in preparation
S92: Redshifts from Schneider et al., 1992AJ....103.1047S 1992AJ....103.1047S
L96: Redshifts from Le Brun et al., 1996A&A...306..691L 1996A&A...306..691L
B98: Redshifts from Bowen et al. 1998MNRAS.297..239B 1998MNRAS.297..239B
Note (2): Weighted mean and weighted uncertainty based on redshifts
measured with 2-3 templates (see Sect. 2.3). For redshifts from the
literature, uncertainties are listed when provided in the original
papers. All redshifts are heliocentric.
Note (3): For a few objects, no magnitude is available from the POSS II
database. In most cases, this indicates that the object is too faint
to be detected in the POSS II survey. However, in some cases this may
be due to misclassification in the POSS II database or close proximity
to a bright star.
Note (4): Absolute magnitude calculated using interstellar extinction
corrections based on E(B-V) from Lockman & Savage, 1995, Cat.
J/ApJS/97/1 and the K-correction from Peebles, 1993, Principles of
Physical Cosmology (Princeton: Princeton Univ. Press), 331.
K=2.5log(1+z).
Note (5): Impact parameter (i.e., projected distance to sight line).
The QSO coordinates (J2000) are
for H1821+643 (table1.dat), RA=18 21 57.2, DE=+64 20 36
for PG 1116+215 (table2.dat), RA=11 19 08.7, DE=+21 19 18
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Byte-by-byte Description of file: table4.dat table5.dat
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Bytes Format Units Label Explanations
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1- 7 F7.2 0.1nm Lambda Vacuum heliocentric wavelength of the line
centroid
8 A1 --- n_Lambda [c] Note on Lambda (1)
10- 13 I4 0.1pm EW ? Observed equivalent width measured as
described in Tripp et al., 1996ApJS..102..239T 1996ApJS..102..239T
15- 16 I2 0.1pm e_EW ? rms uncertainty on EW
17- 18 A2 --- n_EW [a e] Note on EW (1) (3)
19- 22 I4 0.1pm EWi ? For strongly blended lines, individual
equivalent widths derived from profile
parameters measured with VPFIT
25- 39 A15 --- Line Line identification (2)
40 A1 --- n_Line [abd] Note on Line (3) (1)
42- 48 F7.5 --- zabs ? Redshift measured with VPFIT from the
G140L spectrum
50- 52 I3 km/s HV ? Heliocentric line velocity for lines due to
the Galactic ISM
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Note (1): the note means the following:
c: Contaminated by geocoronal O I emission
a: Strongly blended line
Note (2): A colon indicates that the line is a probable detection
but requires confirmation
Note (3): the note means the following:
b: This ISM line may be blended with an extragalactic H I Lyα
line (see text sect. 3.1.1), which could cause this ISM line to
have a more positive velocity than the other ISM lines.
e: The Milky Way lines of Si II 1260.42Å and Si IV 1393.76,
1402.77Å contain substructure implying the detection of a
high-velocity cloud at vISM∼200km/s. This cloud was not detected
in the wideband H I 21 cm observations of Lockman & Savage, 1995,
Cat. J/ApJS/97/1
d: The identification of this line is ambiguous; this could be
Si III 1206.5 associated with the O VI absorber at
zabs=0.22503. However, for reasons noted in the text
(sect. 3.1.2, see also Savage et al., 1998AJ....115..436S 1998AJ....115..436S),
we believe the absorption is dominated by H I Lyα.
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History: From ApJ electronic version
(End) James Marcout, Patricia Bauer [CDS] 20-Jan-2000