J/ApJ/814/40 Nearby galaxy filaments with UV obs. (Wakker+, 2015)
Nearby galaxy filaments and the Lyα forest: confronting simulations and
the UV background with observations.
Wakker B.P., Hernandez A.K., French D.M., Kim T.-S., Oppenheimer B.D.,
Savage B.D.
<Astrophys. J., 814, 40 (2015)>
=2015ApJ...814...40W 2015ApJ...814...40W (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, nearby ; Redshifts ; Spectra, ultraviolet
Keywords: galaxies: halos; intergalactic medium; quasars: absorption lines
ultraviolet: general
Abstract:
Simulations of the formation of large-scale structures predict that
dark matter, low density highly ionized gas, and galaxies form 10 to
40Mpc scale filaments. These structures are easily recognized in the
distribution of galaxies. Here we use Lyα absorption lines to
study the gas in 30x6Mpc filament at cz∼3500km/s, defined using a new
catalog of nearby (cz<10000km/s) galaxies, which is complete down to a
luminosity of about 0.05L* for the region of space analyzed here.
Using Hubble Space Telescope spectra of 24 active galactic nuclei, we
sample the gas in this filament. All of our sightlines pass outside
the virial radius of any known filament galaxy. Within 500kpc of the
filament axis the detection rate is ∼80%, but no detections are seen
more than 2.1Mpc from the filament axis. The width of the Lyα
lines correlates with filament impact parameter and the four BLAs in
our sample occur within 400kpc of the filament axis, indicating
increased temperature and/or turbulence. Comparing to simulations, we
find that the recent Haardt & Madau extragalactic ionizing background
predicts a factor of 3-5 too few ionizing photons. Using a more
intense radiation field matches the hydrogen density profile within
2.1Mpc of the filament axis, but the simulations still overpredict the
detection rate between 2.1 and 5Mpc from the axis. The baryonic mass
inside filament galaxies is 1.4x1013M☉, while the mass of
filament gas outside galaxy halos is found to be 5.2x1013M☉.
Description:
To sample the selected galaxy filament shown in Figure 2, we
constructed a set of 24 targets. First, we correlated the Veron-Veron
QSO catalog with the GALEX database, to find all AGN with UV flux
larger than 1.5x10-15erg/cm2^/s/Å. This gave a list of 75 objects
in the region of interest. We selected most of the brighter ones, but
kept a few fainter targets located in strategic directions. The final
set of 17 targets were observed using the COS on the HST (program
12276), which has a resolution of about 20km/s, allowing us to resolve
the Lyα absorbers. That sample is supplemented by seven targets
in the same region for which archival data are available; these were
mostly obtained using COS, but one case (3C 351.0) was obtained with
the Space Telescope Imaging Spectrograph (STIS). The locations and
program information for each target are given in Table 1.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 80 31 Observations of the 24 targets
table2.dat 99 155 Galaxies between 2400 and 4800km/s within 1Mpc
of each sightline
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See also:
II/294 : The SDSS Photometric Catalog, Release 7 (Adelman-McCarthy+, 2009)
VIII/76 : Leiden/Argentine/Bonn (LAB) Survey of Galactic HI (Kalberla+ 2005)
J/MNRAS/438/3465 : Cosmic web filaments in the SDSS (Tempel+, 2014)
J/MNRAS/437/2017 : HI-galaxy cross-correlation at z≲1 (Tejos+, 2014)
J/ApJS/182/378 : HI and OVI absorbers in nearby Universe (Wakker+, 2009)
J/ApJS/177/39 : Survey of low-redshift OVI absorbers (Tripp+, 2008)
J/ApJ/679/194 : Low-z intergalactic medium. III. (Danforth+, 2008)
J/MNRAS/367/1261 : Redshift survey in 15 quasar fields (Morris+, 2006)
J/AJ/130/873 : Properties of BQS objects in the SDSS DR3 area (Jester+, 2005)
http://archive.stsci.edu/hst/index.html : Hubble Data Archive Home Page
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 15 A15 --- Target Target name
17- 18 I2 h RAh [14/18] Hour of right ascension (J2000)
20- 21 I2 min RAm Minute of right ascension (J2000)
23- 26 F4.1 s RAs Second of right ascension (J2000)
28 A1 --- DE- [+] Sign of declination (J2000)
29- 30 I2 deg DEd [53/71] Degree of declination (J2000)
32- 33 I2 arcmin DEm Arcminute of declination (J2000)
35- 36 I2 arcsec DEs Arcsecond of declination (J2000)
38- 43 F6.4 --- z [0.02/1] Redshift
45- 49 I5 --- PID [8015/12486] HST proposal ID
51- 57 A7 --- PI Program PI
59- 64 A6 --- Dataset HST dataset
66- 75 A10 "Y/M/D" Date Observation date
77- 80 F4.1 s Exp [0.6/26.5] Time exposure
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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- 15 A15 --- Target Target name
17- 39 A23 --- Gal Galaxy name or "Filament axis"
41- 44 I4 km/s Lya1 ? Lyα line detected;
velocity of the absorber (1)
45 A1 --- --- [,]
46- 49 I4 km/s Lya2 ? Other Lyα line detected;
velocity of the absorber (1)
51- 54 I4 km/s cz [2420/4429] cz redshift
56- 60 I5 km/s DelV1 [-1180/1105]? Δν for Lya1 (1)(2)
62- 65 I4 km/s DelV2 [-664/487]? Δν for Lya2 (1)
67- 70 I4 kpc rho [91/6208] Impact parameter ρ
72- 75 F4.1 kpc Diam [1/55.6]? Diameter
77- 80 F4.2 Lsun L/L* [0/4.9]? Luminosity
82- 84 I3 kpc Rvir [3/277]? Virial radius
86- 91 F6.1 --- rho/R [1/1384.9]? Impact parameter to virial
radius ratio
93- 99 A7 --- Type Galaxy type
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Note (1): For AGN toward which an Lyα line is seen (see Section 5),
Lya1 (and Lya2) shows the velocity of the absorber. DelV1 (and DelV2)
then gives the difference between that velocity and the filament
velocity. For example, 3C 351.0 has an Lyα line at 3597km/s,
while the nearest axis segment (at impact parameter 569kpc) is
centered at 3600km/s. This implies that the absorption is offset
by -3km/s from the filament velocity. See section 3.2.
Note (2): In the case of galaxies near the sightline, DelV1 also gives the
difference between ν(Lyα) and ν(galaxy), but only when
that difference is less than ±400km/s and either the impact
parameter is less than 300kpc or the ratio of the impact parameter to
virial radius (rho/R) is less than 2. In other words, a non-blank
entry in this column for a galaxy row means that in a conventional
approach the Lyα absorption could be associated with the galaxy.
See section 3.2.
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History:
From electronic version of the journal
(End) Emmanuelle Perret [CDS] 22-Feb-2016