J/ApJ/806/95 A search for ultra-compact HVC counterparts (Sand+, 2015)
A comprehensive archival search for counterparts to ultra-compact
high-velocity clouds: five local volume dwarf galaxies.
Sand D.J., Crnojevic D., Bennet P., Willman B., Hargis J., Strader J.,
Olszewski E., Tollerud E.J., Simon J.D., Caldwell N., Guhathakurta P.,
James B.L., Koposov S., McLeod B., Morrell N., Peacock M., Salinas R.,
Seth A.C., Stark D.P., Toloba E.
<Astrophys. J., 806, 95 (2015)>
=2015ApJ...806...95S 2015ApJ...806...95S (SIMBAD/NED BibCode)
ADC_Keywords: H I data ; Galaxies, optical ; Ultraviolet
Keywords: galaxies: dwarf; galaxies: individual: (ALFALFA-Dw1, GALFA-Dw1,
GALFA-Dw2, GALFA-Dw3, GALFA-Dw4); radio lines: galaxies
Abstract:
We report five Local Volume dwarf galaxies (two of which are presented
here for the first time) uncovered during a comprehensive archival
search for optical counterparts to ultra-compact high-velocity clouds
(UCHVCs). The UCHVC population of HI clouds are thought to be
candidate gas-rich, low-mass halos at the edge of the Local Group and
beyond, but no comprehensive search for stellar counterparts to these
systems has been presented. Careful visual inspection of all publicly
available optical and ultraviolet imaging at the position of the
UCHVCs revealed six blue, diffuse counterparts with a morphology
consistent with a faint dwarf galaxy beyond the Local Group. Optical
spectroscopy of all six candidate dwarf counterparts show that five
have an Hα-derived velocity consistent with the coincident HI
cloud, confirming their association; the sixth diffuse counterpart is
likely a background object. The size and luminosity of the UCHVC
dwarfs is consistent with other known Local Volume dwarf irregular
galaxies. The gas fraction (MHI/Mstar) of the five dwarfs are
generally consistent with that of dwarf irregular galaxies in the
Local Volume, although ALFALFA-Dw1 (associated with ALFALFA UCHVC
HVC274.68+74.70-123) has a very high MHI/Mstar∼40. Despite the
heterogeneous nature of our search, we demonstrate that the current
dwarf companions to UCHVCs are at the edge of detectability due to
their low surface brightness, and that deeper searches are likely to
find more stellar systems. If more sensitive searches do not reveal
further stellar counterparts to UCHVCs, then the dearth of such
systems around the Local Group may be in conflict with ΛCDM
simulations.
Description:
We have searched all available optical and ultraviolet imaging
archives for counterparts to the ultra-compact high-velocity clouds
(UCHVCs; see section 2.1 and table 1).
In addition to our archival search for counterparts to the UCHVCs, we
have also acquired some supplementary imaging of select systems with
the Magellan/Megacam in 2013 Jun 11 and 2014 Apr 26-27 and the
APO/SPICAM in 2014 Nov 17 (see section 2.2).
We have obtained spectroscopic observations for all six of the strong
dwarf galaxy candidates identified in our search. ALFALFA-Dw1
(HVC274.68+74.70-123) was observed with the Inamori- Magellan Areal
Camera and Spectrograph (IMACS) on the Magellan Baade telescope on
2014 June 17 (UT). GALFA-Dw1 (GALFA source 003.7+10.8+236), also known
as Pisces A was observed on 2014 June 29 (UT) using the Goodman
High-Throughput Spectrograph on the SOAR 4.1m telescope. GALFA-Dw2
(GALFA source 019.8+11.1+617), also known as Pisces B, was observed on
2014 October 21 (UT) with the Blue Channel Spectrograph on the MMT.
GALFA-Dw3 (GALFA source 044.7+13.6+528) and GALFA-Dw4 (GALFA source
086.4+10.8+611) were observed with the 3.5m Astrophysical Research
Consortium Telescope at APO on 2014 November 18 (UT) using the Dual
Imaging Spectrograph (DIS).
The faint, blue optical source coincident with GALFA 162.1+12.5+434
(see Figure 2) was observed on 2014 December 24 (UT) with the Blue
Channel Spectrograph on the MMT.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 121 86 Summary of ultra-compact high-velocity cloud
(UCHVC) archival search
table3.dat 101 6 Spectroscopy log of dwarf galaxy candidates
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See also:
B/cfht : Log of CFHT Exposures (CADC, 1979-)
J/AJ/146/145 : ALFALFA discovery of Leo P. IV. VI photometry (Mcquinn+, 2013)
J/AJ/145/149 : ALFALFA discovery of Leo P. II. BVR photometry (Rhode+, 2013)
J/ApJ/768/77 : Ultra-compact high velocity clouds from ALFALFA (Adams+, 2013)
J/AJ/145/101 : Updated nearby galaxy catalog (Karachentsev+, 2013)
J/ApJ/758/44 : The GALFA-HI compact cloud catalog (Saul+, 2012)
J/ApJ/756/79 : Opt. photometry in 3 Local Group dwarf galaxies (Sand+, 2012)
J/AJ/144/4 : Dwarf galaxies data in the Local Group (McConnachie+, 2012)
J/AJ/142/170 : ALFALFA survey: the α.40 HI sources (Haynes+, 2011)
J/AJ/139/315 : HI-selected galaxies in SDSS. Optical data (West+, 2010)
J/AJ/133/2569 : Arecibo legacy fast ALFA survey III. (Giovanelli+, 2007)
J/ApJ/655/144 : ACS Virgo Cluster Survey. XIII. (Mei+, 2007)
J/AJ/130/873 : Properties of BQS objects in the SDSS DR3 area (Jester+, 2005)
J/MNRAS/361/34 : HIPASS catalogue. III. (Doyle+, 2005)
J/ApJ/623/181 : Compact high-velocity cloud photometry catalog (Siegel+, 2005)
J/AJ/129/1311 : J-band photometry of ADBS Galaxies (Rosenberg+, 2005)
J/AJ/123/873 : HIPASS high-velocity clouds (Putman+, 2002)
J/ApJS/119/159 : Deep survey of HI-selected galaxies (Spitzak+, 1998)
http://www.sdss3.org/ : SDSS-III home page
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 A8 --- Survey Survey (ALFALFA or GALFA-HI)
10- 25 A16 --- ID Ultra-compact high-velocity clouds (UCHVC) ID
(see the "Nomenclature" section below)
27- 28 I2 h RAh [0/23] Hour of Right Ascension (J2000)
30- 31 I2 min RAm Minute of Right Ascension (J2000)
33- 36 F4.1 s RAs Second of Right Ascension (J2000)
38 A1 --- DE- [+] Sign of Declination (J2000)
39- 40 I2 deg DEd [4/36] Degree of Declination (J2000)
42- 43 I2 arcmin DEm Arcminute of Declination (J2000)
45- 46 I2 arcsec DEs Arcsecond of Declination (J2000)
48- 54 F7.2 km/s VLSR [-454/615] HI Local Standard of Rest velocity
56- 75 A20 --- Opt Optical Data
77- 79 A3 --- n_Opt Notes on Opt (1)
81- 87 A7 --- GALEX GALEX Data
89- 91 A3 --- n_GALEX Notes on GALEX (2)
93-121 A29 --- Comm Comments (3)
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Note (1): Notes on Optical Data as follows:
a = DSS images are listed only when it is the only option.
d = Supplementary imaging; Section 2, Table 2 and
the "Description" section above.
e = CFHT (r,) texp=150s
g = CFHT (i,) texp=476s
h = CFHT (u,g,i) texp=(2400, 2760, 3240)s.
i = CFHT (u,g,i,z) texp=(6402, 3170, 2055, 4400)s
j = CFHT (r,) texp=420s
k = CFHT (r,) texp=1600s
l = CFHT (r,) texp=2260s
m = CFHT (r,) texp=200s
n = CFHT (g,) texp=1050s
o = CFHT (u,g,r,i,z) texp=(6800,3100,3720,6000,7500)s
p = CFHT (g,r,i,z) texp=(3170,4461,2055,4400)s
q = CFHT (g,r,i,z) texp=(4800,1400,7500,4400)s
s = CFHT (r,) texp=480s
t = CFHT (r,) texp=240s
u = CFHT (u,g,r,i) texp=(2800,5400,920,470)s
Note (2): Notes on GALEX Data as follows:
b = GALEX Allsky Imaging survey; texp∼100s
c = GALEX Medium Imaging survey; texp∼1500s
f = GALEX Guest Investigator data; NUV,FUV texp=1667s
v = GALEX Guest Investigator data; NUV texp=1730s
w = GALEX Guest Investigator data; FUV,NUV texp=1655,1655s
x = GALEX Guest Investigator data; NUV texp=1650s
y = GALEX Guest Investigator data; NUV texp=1690s
z = GALEX Guest Investigator data; NUV texp=1605s
aa = GALEX Guest Investigator data; NUV texp=1909s
ab = GALEX Guest Investigator data; FUV, NUV texp=1500,1500s
ac GALEX Guest Investigator data; FUV, NUV texp=5057,5057s
Note (3): Notes on Comments:
B14 = Fields with deep imaging reported by Bellazzini et al.
(2015A&A...575A.126B 2015A&A...575A.126B). None of these found dwarf counterparts,
besides ALFALFA-Dw1.
(*) = Candidate diffuse dwarf galaxy at UCHVC position. GALFA-Dw1 and
GALFA-Dw2 are Pisces A and Pisces B, as reported by Tollerud et al.
(2015ApJ...798L..21T 2015ApJ...798L..21T). ALFALFA-Dw1 is SECCO 1 as reported by
Bellazzini et al. (2015ApJ...800L..15B 2015ApJ...800L..15B).
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Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 15 A15 --- Target Target designation
17- 21 A5 --- Survey ("HVC" for ALFALFA or "GALFA" for GALFA-HI)
23- 38 A16 --- ID UCHVC ID
40- 53 A14 --- Tel Telescope/Instrument
55- 65 A11 "YYYY/MMM/DD" Date Observation date
67 I1 --- Exp1 Exposure time 1
68 A1 --- --- [x]
69- 72 I4 --- Exp2 Exposure time 2
74- 77 I4 km/s Vlsr [-114/5730] Hα LSR velocity
79- 81 I3 km/s e_Vlsr [8/200] Vlsr uncertainty
83-101 A19 --- Notes Notes
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Nomenclature Notes:
GALFA-HI sources are <[SPG2012] DDD.d+DD.d+VVV> in Simbad while
ALFALFA sources are in Simbad.
History:
From electronic version of the journal
* 16-Nov-2015: Insert into VizieR
* 24-Feb-2017: Misprint corrected in table 1: ID 087.35-39.78-434 (ALFALFA)
corrected for 087.35-39.78-454
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 12-Oct-2015