J/MNRAS/498/883 Neutral hydrogen evolution over the past 11Gyr (Grasha+, 2020)
The evolution of neutral hydrogen over the past 11 Gyr via H I 21 cm absorption.
Grasha K., Darling J., Leroy A.K., Bolatto A.D.
<Mon. Not. R. Astron. Soc., 498, 883-898 (2020)>
=2020MNRAS.498..883G 2020MNRAS.498..883G (SIMBAD/NED BibCode)
ADC_Keywords: Radio sources ; QSOs ; H I data ; Radio lines ; Redshifts ;
Positional data
Keywords: stars: evolution - galaxies: high-redshift - galaxies: ISM -
quasars: absorption lines - cosmology: observations -
radio lines: galaxies
Abstract:
We present the results of a blind search for intervening HI 21cm
absorption towards 260 radio sources in the redshift range 0<z<2.74
with the Green Bank Telescope. The survey has the sensitivity to
detect sub-damped Ly α (DLA) systems for HI spin temperatures
Ts/f=100K, and despite the successful re-detection of 10 known 21cm
absorbers in the sample, we detect no new absorption lines in the full
survey. Sources detected in 21cm absorption were also searched for
hydroxyl (OH) 18cm absorption and we re-detect 1667MHz OH absorption
towards PKS 1830-211. We searched for intervening HI 21cm absorption
along the line of sight in each source achieving a total redshift
coverage of Δz=88.64 (comoving absorption path of
ΔX=159.5) after removing regions affected by radio frequency
interference. We compute a 95 per cent confidence upper limit on the
column density frequency distribution f(NHI) and set a statistical
constraint on the spin temperature Ts in the range 100-1000K,
consistent with prior redshifted optical DLA surveys and HI 21cm
emission observations at the same redshifts. We infer a value for the
cosmological mass density of neutral gas, ΩHI. Through
comparison with prior ΩHI measurements, we place a statistical
constraint on the mean spin temperature of Ts/f=175K. Our derived
ΩHI values support a relative mild evolution in ΩHI
over the last 11Gyr and are consistent with other methods that measure
ΩHI.
Description:
We select 260 radio sources to search for new intervening 21cm lines
along the sightlines with no requirement placed on the source type.
The sources are selected from the White & Becker (1992ApJS...79..331W 1992ApJS...79..331W,
Cat. VIII/17) catalogue with requirements of a known optical redshift,
north of declination δ≳30deg, and a continuum flux density of
S>0.3Jy at 780MHz.
We observed 89 sources in 2004 January (GBT program 02C-008) for
intervening HI 1420.405752MHz absorption from z=0.6 to z=1.1 at the
Green Bank Telescope (GBT). We chose GBT's Prime Focus (PF) 1 receiver
(PF1-800), covering 680-880MHz (0.6<z<1.1) due to the relatively
minimal RFI present at these frequencies.
These observations are complemented with observations of an additional
182 radio sources between 2004 September and 2005 August (GBT program
04C-018) at the GBT for HI 21cm absorption in intervening HI systems
between z=0 and z=zsource. The redshift coverage is not always
complete for each source. A total of 11 sources appeared in both
observing programs, resulting in a total of 260 unique radio sources
in this survey.
Observations were divided among the GBT receivers as follows: 147
sources were observed with the 1.4GHz L-band receiver (0<z<0.235), 126
with the 1GHz PF 2 receiver (0.150<z<0.570), 204 with the 800MHz
PF1-800 receiver (0.536<z<1.10; including both GBT programs), two with
the 600MHz PF1-600 receiver (1.06<z<1.79), and 12 sources with the
450MHz PF1-450 receiver (1.58<z<2.74). These receivers were selected
to cover the full spectral path for each target from z=0 to the
redshift of the source.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 182 261 Journal of Observations
table2.dat 145 29 Sources with HI 21cm absorption
table3.dat 193 16 Properties of the HI 21cm and OH 18cm Line
Observations
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See also:
VIII/17 : The North 20cm Survey (White+ 1992)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 21 A21 --- Name Source name
23 A1 --- f_Name [abc] Flag on Name (1)
25- 26 I2 h RAh Right ascension (J2000)
28- 29 I2 min RAm Right ascension (J2000)
31- 35 F5.2 s RAs Right ascension (J2000)
37 A1 --- DE- Declination sign (J2000)
38- 39 I2 deg DEd Declination (J2000)
41- 42 I2 arcmin DEm Declination (J2000)
44- 47 F4.1 arcsec DEs Declination (J2000)
49- 56 F8.6 --- z Optical redshift of the background radio
object
58- 64 F7.5 --- e_z ? Error on z
66- 68 I3 s T1.4 Total integration time spent on the reduced
spectrum for the 1.4GHz bandpass (2)
70- 73 F4.1 mJy rms1.4 ? Average measured spectral noise level for
the 1.4GHz bandpass (2)
75 A1 --- f_rms1.4 [*] Flag on rms1.4 (3)
77- 82 F6.3 Jy S1.4 ? Flux limit measured as closely to 1420
MHz (2)
84 A1 --- l_NHI1.4 Limit flag on NHI1.4
86- 90 F5.3 10+18/cm2 NHI1.4 ? Column density limit measured as closely
to 1420 MHz (2)
92- 94 I3 s T1.0 Total integration time spent on the reduced
spectrum for the 1.0GHz bandpass (4)
96- 99 F4.1 mJy rms1.0 ? Average measured spectral noise level for
the 1.0GHz bandpass (4)
101 A1 --- f_rms1.0 [*] Flag on rms1.0 (3)
103- 108 F6.3 Jy S1.0 ? Flux limit measured as closely to 1000
MHz (4)
110 A1 --- l_NHI1.0 Limit flag on NHI1.0
112- 116 F5.3 10+18/cm2 NHI1.0 ? Column density limit measured as closely
to 1000MHz (4)
118- 121 I4 s T800 Total integration time spent on the reduced
spectrum for the 800MHz bandpass (5)
123- 126 F4.1 mJy rms800 ? Average measured spectral noise level for
the 800MHz bandpass (5)
128 A1 --- f_rms800 [*] Flag on rms800 (3)
130- 135 F6.3 Jy S800 ? Flux limit measured as closely to 800 MHz
(5)
137- 141 F5.3 Jy e_S800 ? Error on S800
143 A1 --- l_NHI800 Limit flag on NHI800
145- 149 F5.3 10+18/cm2 NHI800 ? Column density limit measured as closely
to 800MHz (5)
151- 153 I3 s T450 Total integration time spent on the reduced
spectrum for the 450MHz bandpass (6)
155- 158 F4.1 mJy rms450 ? Average measured spectral noise level for
the 450MHz bandpass (6)
160 A1 --- f_rms450 [*] Flag on rms450 (3)
162- 166 F5.3 Jy S450 ? Flux limit measured as closely to 450MHz
(6)
168 A1 --- l_NHI450 Limit flag on NHI450
170- 173 F4.2 10+18/cm2 NHI450 ? Column density limit measured as closely
to 450MHz (6)
175- 180 F6.4 --- Dztot ? Total redshift searched per source in all
the receivers
182 A1 --- f_Dztot [*] Flag on Dztot (3)
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Note (1): Flag as follows:
a = Only two sources were observed with the GBT's PF1-600 receiver,
0016+731 and SBS 0804+499 with 516 and 596s, respectively. The entire
spectral range for 0016+731 was affected by RFI and the average measured
spectral noise level for SBS 0804+499 was 16mJy and a column density
limit of N<3.6x1020cm-2 at 600MHz.
b = This source was observed in the 800MHz band in both GBT programs. The
observations from the 02C-008 program suffer less RFI and are used for
this band throughout this paper.
c = This source was observed in the 800MHz band in both GBT programs. The
observations from the 04C-018 program suffer less RFI and are used for
this band throughout this paper.
Note (2): The L band covers the range of 0<z<0.235 (1150-1420MHz)
Note (3): Flag as follows:
* = Presence of radio frequency interference (RFI)
Note (4): PF2 covers the range of 0.150<z<0.570 (905-1235MHz)
Note (5): PF1-800 covers 0.536<z<1.10 (675-925MHz)
Note (6): PF1-450 covers 1.58<z<2.74 (380-550MHz)
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 13 A13 --- Name Source name
15 A1 --- f_Name [a] Flag on Name (1)
17- 19 A3 --- Comp Numbered Gaussian component
21- 29 F9.4 MHz nu Central frequency of each component
31- 36 F6.4 MHz e_nu Error on nu
38- 46 F9.7 --- z Redshift of each absorption feature
48- 56 F9.7 --- e_z Error on z
58- 64 F7.4 Jy Fcont Continuum flux density
66- 71 F6.4 Jy e_Fcont Error on Fcont
73- 77 F5.1 kHz FWHM Observed width of the line
79- 82 F4.1 kHz e_FWHM Error on FWHM
84- 89 F6.2 km/s FWHMrf Rest-frame line width
91- 94 F4.1 km/s e_FWHMrf Error on FWHMrf
96- 99 I4 mJy Depth Depth of the absorption line
101- 102 I2 mJy e_Depth Error on Depth
104- 108 F5.2 10-2 tau Peak optical depth
110- 113 F4.2 10-2 e_tau Error on tau
115- 120 F6.3 10+18/cm2/K NHI Derived HI column density NHI/ (Ts/f)
122- 126 F5.3 10+18/cm2/K e_NHI Error on NHI
128- 132 F5.2 10+18/cm2/K NHIlit ? Measured HI column density
NHI/(Ts/f) from previous 21 cm
observations
134- 137 F4.2 10+18/cm2/K e_NHIlit ? Error on NHIlit
139- 141 A3 --- r_NHIlit Reference for NHIlit (2)
143- 145 I3 K Ts/f ? Measured Ts/f values constrained from
Lyα and VLA observations from
Kanekar et al. (2014MNRAS.438.2131K 2014MNRAS.438.2131K)
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Note (1): Flag as follows:
a = Intrinsic 21 cm absorption line
Note (2): References as follows:
1 = Carilli, Rupen & Yanny (1993ApJ...412L..59C 1993ApJ...412L..59C)
2 = Briggs et al. (1989ApJ...341..650B 1989ApJ...341..650B)
3 = Lane & Briggs (2001ApJ...561L..27L 2001ApJ...561L..27L)
4 = Wolfe et al. (1985ApJ...294L..67W 1985ApJ...294L..67W)
5 = Lane et al. (1998AJ....116...26L 1998AJ....116...26L)
6 = Vermeulen et al. (2003A&A...404..861V 2003A&A...404..861V)
7 = Brown & Roberts (1973ApJ...184L...7B 1973ApJ...184L...7B)
8 = Chengalur et al. (1999A&A...343L..79C 1999A&A...343L..79C)
9 = Darling et al. (2004ApJ...613L.101D 2004ApJ...613L.101D)
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 13 A13 --- Name Source name
15- 17 A3 --- f_Name Flag on Name (1)
19- 26 F8.6 --- zabs Redshift of known intervening 21cm
absorbers (2)
28- 33 F6.4 --- e_zabs ? Error on zabs
35- 42 F8.3 MHz nuHI Observed frequency for the HI 21cm
line
44- 48 F5.3 MHz e_nuHI ? Error on nuHI
50- 59 A10 km/s DvHI Velocity range for the HI 21cm line
search
61- 64 F4.1 mJy rmsHI ? Measured rms noise over the searched
region for the HI 21cm line
66 A1 --- f_rmsHI [*] Flag on rmsHI (3)
68- 72 F5.3 Jy contHI ? Continuum flux density for the HI
21cm line
74- 78 F5.3 Jy e_contHI ? Error on contHI
80 A1 --- l_NHI Limit flag on NHI
82- 86 F5.2 10+18/cm2/K NHI ? Derived 3σ upper limit to the
HI column density
88- 90 F3.1 10+18/cm2/K e_NHI ? Error on NHI
92- 98 F7.2 MHz nuOH1612 Observed frequency for the OH 1612MHz
line
100- 110 A11 km/s DvOH1612 Velocity range for the OH 1612MHz line
search
112- 115 F4.1 mJy rmsOH1612 ? Measured rms noise over the searched
region for the OH 1612MHz line
117 A1 --- f_rmsOH1612 [*] Flag on rmsOH1612 (3)
119- 125 F7.2 MHz nuOH1667 Observed frequency for the OH 1667MHz
line
127- 136 A10 km/s DvOH1667 Velocity range for the OH 1667MHz line
search
138- 140 F3.1 mJy rmsOH1667 ? Measured rms noise over the searched
region for the OH 1667MHz line
142 A1 --- f_rmsOH1667 [*] Flag on rmsOH1612 (3)
144- 150 F7.2 MHz nuOH1720 Observed frequency for the OH 1720MHz
line
152- 161 A10 km/s DvOH1720 Velocity range for the OH 1720MHz line
search
163- 165 F3.1 mJy rmsOH1720 ? Measured rms noise over the searched
region for the OH 1720MHz line
167 A1 --- f_rmsOH1720 [*] Flag on rmsOH1612 (3)
169- 174 F6.4 Jy contOH ? OH continuum flux density (4)
176- 181 F6.4 Jy e_contOH ? Error on contOH
183 A1 --- l_NOH Limit flag on NOH
185- 189 F5.1 10+13/cm2/K NOH ? Derived 3σ upper limit to the
HI column density (4)
191 I1 10+13/cm2/K e_NOH ? Error on NOH
193 A1 --- f_NOH [c] Flag on NOH (5)
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Note (1): Flag as follows:
a = Sources searched for possible intrinsic HI and OH absorption
b = The corresponding 21cm absorbers at the same redshift remain undetected
due to the expected 21cm absorber lying outside the redshift coverage
or is irrecoverable due to RFI
d = We do not reach sufficient signal to noise to detect the known OH
satellite lines at 1612 and 1720MHz towards 1413+135 at zabs=0.24671
(Darling 2004ApJ...612...58D 2004ApJ...612...58D; Kanekar et al. 2004PhRvL..93e1302K 2004PhRvL..93e1302K). We do
not detect the 1665 or 1667MHz OH absorption at the same redshift
towards this system (Kanekar & Chengalur 2002A&A...381L..73K 2002A&A...381L..73K) with a
reported column density of NOH/Tx=5.1x1013cm-2K-1.
Note (2): Or redshift of the host galaxy in the case of intrinsic absorbers
with a redshift lying in our spectral coverage
Note (3): Flag as follows:
* = Presence of radio frequency interference (RFI)
Note (4): The OH continuum flux density and OH column density limit are
computed for the 1667MHz line unless stymied by RFI
Note (5): Flag as follows:
c = Chengalur et al. (1999A&A...343L..79C 1999A&A...343L..79C) measures an OH column density of
NOH/Tx=40x1013cm-2K-1
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History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 01-Aug-2023