J/A+A/570/A61 PM-selected stars of Hercules galaxy (Fabrizio+, 2014)
A bag of tricks: Using proper motions of Galactic stars to identify the Hercules
ultra-faint dwarf galaxy members.
Fabrizio M., Raimondo G., Brocato E., Bellini A., Libralato M., Testa V.,
Cantiello M., Musella I., Clementini G., Carini R., Marconi M., Piotto G.,
Ripepi V., Buonanno R., Sani E., Speziali R.
<Astron. Astrophys. 570, A61 (2014)>
=2014A&A...570A..61F 2014A&A...570A..61F
ADC_Keywords: Galaxies, photometry
Keywords: galaxies: dwarf - Local Group - methods: observational
Abstract:
Discovered in the last decade as overdensities of resolved stars, the
ultra-faint dwarfs (UFDs) are among the least luminous, most
dark-matter dominated, and most metal-poor galaxies known today. They
appear as sparse, loose objects with high mass-to-light ratios.
Hercules is the prototype of the UFD galaxies. To date, there are
still no firm constraints on its total luminosity due to the
difficulty of disentangling Hercules bona-fide stars from the severe
Galactic field contamination.
To better constrain Hercules properties, we aim at removing foreground
and background contaminants in the galaxy field using the proper
motions of the Milky Way stars and the colour-colour diagram.
We have obtained images of Hercules in the rSloan , BBessel and
Uspec bands with the Large Binocular Telescope (LBT) and LBC-BIN
mode capabilities. The rSloan new dataset combined with data from
the LBT archive span a time baseline of about 5yr, allowing us to
measure proper motions of stars in the Hercules direction for the
first time. The Uspec data along with existing LBT photometry
allowed us to use colour-colour diagram to further remove the field
contamination.
Description: The Hercules ultra-faint dwarf (UFD) galaxy (J2000
position 16:31:02.0+12:47:25.6) was observed with the Large Binocular
Camera (LBC) at the LBT located on Mount Graham in Arizona. The LBC is
a wide field imager (4 CCDs, 2Kx4.5K pixels each) with a FoV of ∼23'x
23' and a resolution of 0.225"/pix. We employed both archival and
proprietary data to have the longest available time baseline.
File table2 contains the final catalogue of 528 PM-selected sources.
From left to right we report: the source identity (Col. 1), right
ascension and declination (Col. 2-3), Uspec, BBessel and rSloan
magnitudes with their uncertainty (Col. 4-6), displacement with its
uncertainty (Col. 7)
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 71 528 PM-selected stars of Hercules UFD galaxy
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See also:
J/MNRAS/317/801 : LBDS Hercules sample griJHK photometry (Waddington+, 2000)
J/ApJ/704/898 : Photometry of the Hercules dwarf galaxy (Sand+, 2009)
J/ApJ/756/121 : Variable stars in Her dwarf galaxy (Musella+, 2012)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- ID [1/528] Name of the source
5- 16 F12.8 deg RAdeg Right ascension (J2000.0)
18- 28 F11.8 deg DEdeg Declination (J2000.0)
30- 34 F5.2 mag Umag ?=99.99 Uspec magnitude
36- 39 F4.2 mag e_Umag ?=9.99 Uspec magnitude uncertainty
41- 45 F5.2 mag rmag Sloan r magnitude
47- 50 F4.2 mag e_rmag Sloan r magnitude uncertainty
52- 56 F5.2 mag Bmag Bessel B magnitude
58- 61 F4.2 mag e_Bmag Bessel B magnitude uncertainty
63- 66 F4.2 0.2pix/yr Delta Displacement Δ (in pix/4.94yr, or
46mas/yr with a scale of 0.225arcsec/pix)
68- 71 F4.2 0.2pix/yr e_Delta Displacement uncertainty
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Acknowledgements:
Michele Fabrizio, fabrizio(at)oa-teramo.inaf.it
(End) Patricia Vannier [CDS] 23-Aug-2014