J/ApJ/808/136 UV counterparts in HI clouds using ALFA surveys (Donovan+, 2015)
Finding gas-rich dwarf galaxies betrayed by their ultraviolet emission.
Donovan Meyer J., Peek J.E.G., Putman M., Grcevich J.
<Astrophys. J., 808, 136 (2015)>
=2015ApJ...808..136D 2015ApJ...808..136D (SIMBAD/NED BibCode)
ADC_Keywords: Diffuse clouds ; H I data ; Photometry, ultraviolet
Keywords: catalogs - galaxies: dwarf - Local Group - ultraviolet: galaxies
Abstract:
We present ultraviolet (UV) follow-up of a sample of potential dwarf
galaxy candidates selected for their neutral hydrogen (HI) properties,
taking advantage of the low UV background seen by the GALEX satellite
and its large and publicly available imaging footprint. The HI clouds,
which are drawn from published Galactic Arecibo L-band Feed Array and
Arecibo Legacy Fast Arecibo L-band Feed Array HI survey compact cloud
catalogs, are selected to be galaxy candidates based on their spatial
compactness and non-association with known high-velocity cloud
complexes or Galactic HI emission. Based on a comparison of their UV
characteristics to those of known dwarf galaxies, half (48%) of the
compact HI clouds have at least one potential stellar counterpart with
UV properties similar to those of nearby dwarf galaxies. If they are
galaxies, then the star formation rates, HI masses, and star formation
efficiencies of these systems follow the trends seen for much larger
galaxies. The presence of UV emission is an efficient method to
identify the best targets for spectroscopic follow-up, which is
necessary to prove that the stars are associated with compact HI.
Furthermore, searches of this nature help to refine the salient HI
properties of likely dwarfs (even beyond the Local Group). In
particular, HI compact clouds considered to be velocity outliers
relative to their neighbor HI clouds have the most significant
detection rate of single, appropriate UV counterparts. Correcting for
the sky coverage of the two all-Arecibo sky surveys yielding the
compact HI clouds, these results may imply the presence of potentially
hundreds of new tiny galaxies across the entire sky.
Description:
GALFA-HI is a survey of Galactic HI conducted with the ALFA seven-beam
feed array on the 305 m Arecibo antenna. The survey has both high spatial
(FWHM∼4') and velocity (0.18 km/s) resolution over 13000 (7520 in DR1)
degrees2 of sky between -650 and 650 km/s. Details of the observations
and data reduction can be found in Peek et al. (2011ApJS..194...20P 2011ApJS..194...20P).
The ALFALFA HI-line survey, now 40% complete, also uses the Arecibo
Observatory and its seven-beam feed array to detect potential dwarf
galaxies in the vicinity of the Milky Way. The survey, which covers
over 7000 (2800 in α.40) deg2 of sky out to 18000 km/s, has the
sensitivity to detect 105 M☉ clouds with 20 km/s linewidths at
a distance of 1 Mpc.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 87 98 Summary of HI Clouds
table2.dat 92 29 Single Counterpart Candidates (SCCs)
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See also:
J/AJ/138/338 : Arecibo Legacy Fast ALFA Survey. IX. (Stierwalt+, 2009)
J/ApJ/722/395 : Compact H I clouds from the GALFA-H I survey (Begum+, 2010)
J/AJ/142/170 : ALFALFA survey: the α.40 HI source catalog
(Haynes+, 2011)
J/ApJS/192/6 : A GALEX UV imaging survey of nearby galaxies (Lee+, 2011)
J/AJ/143/133 : Properties of dwarf galaxies from the ALFALFA survey
(Huang+, 2012)
J/ApJ/758/44 : The GALFA-HI compact cloud catalog (Saul+, 2012)
J/ApJ/768/77 : Ultra-compact high velocity clouds from ALFALFA (Adams+, 2013)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- Number [1/98] Cloud number
4- 12 F9.5 deg RAdeg Right Ascension in decimal degrees (J2000)
14- 21 F8.5 deg DEdeg Declination in decimal degrees (J2000)
23- 26 I4 km/s VLSR Local Standard of Rest velocity
28- 31 I4 km/s VGSR Galactic Standard of Rest velocity
33- 36 I4 km/s VLGSR Local Group Standard of Rest velocity
38- 41 F4.2 Jy.km/s SHI Integrated HI flux density
43- 46 F4.1 arcmin Size Size
48- 51 F4.1 km/s FWHM FWHM of the HI line
53- 56 F4.1 --- S/N HI signal-to-noise ratio
58- 61 I4 s tNUV NUV exposure time
63- 66 I4 s tFUV FUV exposure time
68- 85 A18 --- Cat Compact cloud catalog containing detection (1)
87 I1 --- Group [0/2]? Group of detected UV counterparts (2)
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Note (1): Catalog as follows:
S12 = Saul et al. 2012, J/ApJ/758/44;
G14 = Grcevich et al. submitted;
A13 = Adams et al. 2013, J/ApJ/768/77.
The GALFA-HI catalogs are broken down further into the detection methods, as
follows:
HI = High HI column density;
S/N = High S/N list;
VEL = Velocity outliers.
Note (2): Group as follows:
0 = Zero counterparts;
1 = One counterpart, or "single counterpart candidates" (SCC);
2 = Multiple counterparts.
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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- 2 I2 --- Number [1/88] Cloud number
4- 11 F8.4 deg RAdeg Right Ascension in decimal degrees (J2000)
13- 20 F8.5 deg DEdeg Declination in decimal degrees (J2000)
22- 26 F5.2 mag NUVmag GALEX NUV AB magnitude
28- 31 F4.2 mag e_NUVmag Uncertainty in NUVmag
33- 37 F5.2 mag FUVmag GALEX FUV AB magnitude
39- 42 F4.2 mag e_FUVmag Uncertainty in FUVmag
44- 48 F5.2 arcsec MajAxis Major axis size
50- 54 F5.2 arcsec MinAxis Minor axis size
56- 58 F3.1 Mpc b_Dist Distance range, lower value
60- 63 F4.1 Mpc B_Dist Distance range, upper value
65- 67 F3.1 10+6Msun b_MHI HI mass range, lower value
69- 73 F5.1 10+6Msun B_MHI HI mass range, upper value
75- 78 F4.1 10-5Msun/yr b_SFR Star Formation Rate range, lower value
80- 85 F6.1 10-5Msun/yr B_SFR Star Formation Rate range, upper value
87- 92 F6.1 10-12/yr SFE Star Formation Efficiency (SFE=SFR/MHI)
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History:
From electronic version of the journal
(End) Prepared by Tiphaine Pouvreau [CDS] 27-Oct-2017