J/AJ/136/713 Arecibo legacy fast ALFA survey. VI. (Kent+, 2008)
The Arecibo legacy fast ALFA survey.
VI. Second HI source catalog of the Virgo cluster region.
Kent B.R., Giovanelli R., Haynes M.P., Martin A.M., Saintonge A.,
Stierwalt S., Balonek T.J., Brosch N., Koopmann R.A.
<Astron. J., 136, 713-724 (2008)>
=2008AJ....136..713K 2008AJ....136..713K
ADC_Keywords: Surveys ; H I data ; Galaxies, radio ; Redshifts
Keywords: galaxies: distances and redshifts - galaxies: halos
galaxies: luminosity function, mass function - galaxies: photometry
galaxies: spiral - radio lines: galaxies
Abstract:
We present the third installment of HI sources extracted from the
Arecibo Legacy Fast ALFA extragalactic survey. This data set continues
the work of the Virgo ALFALFA catalog. The catalogs and spectra
published here consist of data obtained during the 2005 and 2006
observing sessions of the survey. The catalog consists of 578 HI
detections within the range 11h36m<RA(J2000)<13h52m and
+08°<DE(J2000)<+12°, and cz☉<18000km/s. The catalog
entries are matched with optical counterparts where possible through
the examination of digitized optical images. The catalog detections
can be classified into three categories: (a) detections of high
reliability with a signal-to-noise ratio (S/N)>6.5; (b) high-velocity
clouds in the Milky Way or its periphery; and (c) signals of lower S/N
which coincide spatially with an optical object and known redshift.
75% of the sources are newly published HI detections. Of particular
note is a complex of HI clouds projected between M87 and M49 that do
not coincide with any optical counterparts. Candidate objects without
optical counterparts are few. Position corrections for telescope
pointing errors are applied to the data set by comparing the ALFALFA
continuum centroid with those cataloged in the NRAO VLA Sky Survey
(NVSS, Cat. VIII/65). The uncorrected positional accuracy averages
27"(21" median) for all sources with S/N>6.5 and is of order ∼21"(16"
median) for signals with S/N>12. Uncertainties in distances toward the
Virgo cluster can affect the calculated HI mass distribution.
Description:
ALFALFA utilizes a fixed azimuth drift mode observation scheme with
the seven-element ALFA multi-beam receiver system. Beam maps of each
feed can be found in Paper I (2005AJ....130.2598G 2005AJ....130.2598G).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 107 578 HI Candidate Detections
notes.dat 152 124 Comments from section 3.1
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See also:
VIII/77 : HI spectral properties of galaxies (Springob+, 2005)
VIII/73 : HI Parkes All Sky Survey Catalogue (HIPASS) (Meyer+, 2004)
J/AJ/113/905 : HI observations of galaxies (Pantoja+ 1997)
J/MNRAS/357/819 : Colours and HI line observations in Virgo (Sabatini+, 2005)
J/AJ/130/2613 : The Arecibo Legacy Fast ALFA survey. II (Giovanelli+, 2005)
J/AJ/133/2569 : Arecibo legacy fast ALFA survey III. (Giovanelli+, 2007)
J/AJ/135/588 : Arecibo legacy fast ALFA survey V. (Saintonge+, 2008)
http://arecibo.tc.cornell.edu/hiarchive : ALFALFA data access
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 A2 --- --- [3-]
3- 5 I3 --- ALFALFA3 Catalog entry number (3-NNN)
7- 12 I6 --- AGC Arecibo General Catalog number (Cat. VIII/77)
14- 15 I2 h RAh Hour of Right Ascension (J2000) (1)
17- 18 I2 min RAm Minute of Right Ascension (J2000) (1)
20- 23 F4.1 s RAs Second of Right Ascension (J2000) (1)
25 A1 --- DE- Sign of the Declination (J2000) (1)
26- 27 I2 deg DEd Degree of Declination (J2000) (1)
29- 30 I2 arcmin DEm Arcminute of Declination (J2000) (1)
32- 33 I2 arcsec DEs Arcsecond of Declination (J2000) (1)
35- 36 I2 h RAOh ? Counterpart Right Ascension (J2000) (2)
38- 39 I2 min RAOm ? Counterpart Right Ascension (J2000) (2)
41- 44 F4.1 s RAOs ? Counterpart Right Ascension (J2000) (2)
46 A1 --- DEO- Counterpart Declination sign (J2000) (2)
47- 48 I2 deg DEOd ? Counterpart Declination (J2000) (2)
50- 51 I2 arcmin DEOm ? Counterpart Declination (J2000) (2)
53- 54 I2 arcsec DEOs ? Counterpart Declination (J2000) (2)
56- 60 I5 km/s cz Heliocentric velocity (3)
62- 64 I3 km/s W50 Velocity width (4)
66- 68 I3 km/s e_W50 Error in W50 (5)
70- 74 F5.2 Jy.km/s Fc Integrated flux density (6)
76- 79 F4.2 Jy.km/s e_Fc Estimated uncertainty in Fc (7)
81- 85 F5.1 --- S/N Signal-to-noise of detection (8)
87- 90 F4.2 mJy rms Noise figure of spatially integrated spectral
profile (9)
92- 97 F6.2 Mpc Dist ? Adopted distance (10)
99-103 F5.2 [solMass] logM ? Log of HI mass (11)
105 I1 --- Qual Source quality code (12)
107 A1 --- n_ALFALFA3 [*] Indicates additional comments in
notes.dat file
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Note (1): Centroid position of the HI source. The listed position has been
corrected for systemic pointing errors. Positional accuracy is
discussed in section 5.
Note (2): Position of the most likely optical counterpart of the HI
detection. The listed position has been examined by eye using SDSS or
the Digital Sky Survey. The centroid accuracy is ≲2". Optical images
are examined for counterparts based on spatial proximity, morphology,
color, and redshift. If no optical counterpart can be clearly
identified, no optical position is recorded in the catalog;
high-velocity cloud detections are included in this category.
Comments are provided if a preferable source is identified and
other possible candidates are present in the field.
Note (3): Of the HI source, measured as the midpoint between the channels
at which the flux density drops to 50% of each of the two peaks (or of
one, if only one is present) at each side of the spectral feature. The
error adopted is half the error on the width, W50.
Note (4): Measured at the 50% level of each of the two peaks, as described
in Note 3. This value is corrected for instrumental broadening. No
corrections due to turbulent motions, disk inclination or cosmological
effects are applied. The instrumental correction used is that
described by Springob et al. (2005, Cat. VIII/77). Therefore, the
expression for W50=sqrt{W50uncorr2-(2Δν)2} where
Δν is the channel separation in km/s.
Note (5): This error is the sum in quadrature of two components: the first
is a statistical error, principally dependent on the S/N ratio of the
feature measured; the second is a systematic error associated with the
subjective guess with which the observer estimates the spectral
boundaries of the feature: maximum and minimum guesses of the spectral
extent of the feature are flagged and the ratio of those values is
used to estimate systematic errors on the width, the velocity and the
flux integral. In the majority of cases, the systematic error is
significantly smaller than the statistical error; thus the former is
ignored.
Note (6): This is measured on the integrated spectrum, obtained by
spatially integrating the source image over a solid angle of at least
7'x7' and dividing by the sum of the survey beam values over the same
set of image pixels (Shostak & Allen, 1980A&A....81..167S 1980A&A....81..167S). Estimates
of integrated fluxes for very extended sources with significant
angular asymmetries can be misestimated by our algorithm, which is
optimized for measuring sources comparable with or smaller than the
survey beam. A special catalog with parameters of extended sources
will be produced after completion of the survey.
Note (7): Uncertainties associated with the quality of the baseline fitting
are not included; an analysis of that contribution to the error will
be presented elsewhere for the full survey. See the description in
Note 5 for the contribution of a possible systematic measurement
error.
Note (8): Estimated as S/N=((1000Fc)/W50)x(wsmo1/2/rms). The ratio
1000Fc/W50 is the mean flux across the feature, wsmo is either
W50/(2x10) for W50<400km/s or 400/(2x10)=20 for W50≥400km/s [wsmo
is a smoothing width expressed as the number of spectral resolution
bins of 10km/s bridging half of the signal width].
Note (9): The noise figure as tabulated is the r.m.s. as measured over the
signal- and RFI-free portions of the spectrum, after Hanning smoothing
to a spectral resolution of 10km/s.
Note (10): For objects with czcmb>3000km/s, the distance is simply
czcmb/H0; czcmb is the recessional velocity measured in the
Cosmic Microwave Background reference frame and H0 is the Hubble
constant, for which we use a value of 72km/s/Mpc. For objects of lower
czcmb, we use a peculiar velocity model for the local Universe, as
described in Paper II (Giovanelli et al., 2005, Cat. J/AJ/130/2613).
Objects which are thought to be parts of clusters or groups are
assigned the czcmb of the cluster or group. Cluster and group
membership are assigned following the method described in Springob et
al. (2007, Cat. J/ApJS/172/599).
Note (11): Obtained by using the expression MHI=2.356x106Dist2Fc.
Note (12): Quality is numbered with values:
1 = S/N and general qualities make it a reliable detection.
2 = low S/N (<6.5), which would ordinarily not be considered a reliable
detection by the criteria set for code 1. However, HI candidate
source is matched with an optical counterpart with known optical
redshifts which match those measured in the HI line.
9 = assumed to be a HVC.
See text for additional details.
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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- 2 A2 --- --- [3-]
3- 5 I3 --- ALFALFA3 Catalog entry number (3-NNN)
7-152 A146 --- Note Section 3.1 comment
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History:
* 13-Aug-2009: From electronic version of the journal
* 28-Jan-2010: zero values for optical positions, distances
and HI masses removed
References:
Giovanelli et al., Paper I 2005AJ....130.2598G 2005AJ....130.2598G
Giovanelli et al., Paper II 2005AJ....130.2613G 2005AJ....130.2613G, Cat. J/AJ/130/2613
Giovanelli et al., Paper III 2007AJ....133.2569G 2007AJ....133.2569G, Cat. J/AJ/133/2569
Saintonge et al., Paper IV 2007AJ....133.2087S 2007AJ....133.2087S
Saintonge et al., Paper V 2008AJ....135..588S 2008AJ....135..588S, Cat. J/AJ/135/588
Kent et al., Paper VII 2009ApJ...691.1595K 2009ApJ...691.1595K
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 15-Jul-2009