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J/ApJ/704/898     Photometry of the Hercules dwarf galaxy        (Sand+, 2009)

The star formation history and extended structure of the Hercules Milky Way satellite. Sand D.J., Olszewski E.W., Willman B., Zaritsky D., Seth A., Harris J., Piatek S., Saha A. <Astrophys. J., 704, 898-914 (2009)> =2009ApJ...704..898S
ADC_Keywords: Galaxies, photometry ; Galaxies, nearby Keywords: galaxies: dwarf - Local Group Abstract: We present imaging of the recently discovered Hercules Milky Way satellite and its surrounding regions to study its structure, star formation history and to thoroughly search for signs of disruption. We robustly determine the distance, luminosity, size, and morphology of Hercules utilizing a bootstrap approach to characterize our uncertainties. We derive a distance to Hercules via a comparison to empirical and theoretical isochrones, finding a best match with the isochrone of M92, which yields a distance of 133±6kpc. As previous studies have found, Hercules is very elongated, with ε=0.67±0.03 and a half-light radius of rh∼230pc. Using the color-magnitude-fitting package StarFISH, we determine that Hercules is old (>12Gyr) and metal-poor ([Fe/H]~-2.0), with a spread in metallicity, in agreement with previous spectroscopic work. This result is robust with respect to slight variations in the distance to Hercules and mismatches between the observed Hercules color-magnitude diagram and theoretical isochrones. We infer a total absolute magnitude of MV=-6.2±0.4. Our innovative search for external Hercules structure both in the plane of the sky and along the line of sight yields some evidence that Hercules is embedded in a larger stream of stars. A clear stellar extension is seen to the northwest with several additional candidate stellar overdensities along the position angle of Hercules out to ∼35' (∼1.3kpc). Description: Observations of Hercules were, with one exception, taken during 2008 May and June during normal operations of the Large Binocular Telescope (LBT), fitted with the red and blue channels of the Large Binocular Camera. The B- and V-band images for the central Hercules field were taken during Science Demonstration Time (SDT) and were presented in Coleman et al. (2007ApJ...668L..43C). When necessary, we adopted SDSS-DR6 photometry directly for stars brighter than and near the saturation limit of a given LBT field (which depends both on the observing conditions and point spread function). In this case, g and r magnitudes are converted to B magnitudes via the relations found by Jordi et al. (2006A&A...460..339J). File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table2.dat 77 24818 Hercules photometry - central field table3.dat 63 43637 Hercules photometry - adjacent fields
Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
1- 5 I5 --- Seq Star identification number 7- 15 F9.5 deg RAdeg Right Ascension in decimal degrees (J2000) 17- 24 F8.5 deg DEdeg Declination in decimal degrees (J2000) 26- 30 F5.2 mag Bmag B band magnitude 32- 35 F4.2 mag e_Bmag Error in Bmag 37- 40 F4.2 mag AB B band extinction (1) 42- 46 F5.2 mag Vmag V band magnitude 48- 51 F4.2 mag e_Vmag Error in Vmag 53- 56 F4.2 mag AV V band extinction (1) 58- 62 F5.2 mag rmag r band magnitude 64- 67 F4.2 mag e_rmag Error in rmag 69- 72 F4.2 mag Ar r band extinction (1) 74- 77 A4 --- Obs [LBT/SDSS] Observed by SDSS or LBT (Large Binocular Telescope)
Note (1): extinction from Schlegel et al. (1998ApJ...500..525S) dust maps
Byte-by-byte Description of file: table3.dat
Bytes Format Units Label Explanations
1- 5 I5 --- Seq Star identification number 7- 15 F9.5 deg RAdeg Right Ascension in decimal degrees (J2000) 17- 24 F8.5 deg DEdeg Declination in decimal degrees (J2000) 26- 30 F5.2 mag Bmag B band magnitude 32- 35 F4.2 mag e_Bmag Error in Bmag 37- 40 F4.2 mag AB B band extinction 42- 46 F5.2 mag rmag r band magnitude 48- 51 F4.2 mag e_rmag Error in rmag 53- 56 F4.2 mag Ar r band extinction 58 I1 --- F [1,4] Field number (1) 60- 63 A4 --- Obs [LBT/SDSS] Observed by SDSS or LBT (Large Binocular Telescope)
Note (1): Smoothed contour plots of Hercules and adjacent fields are presented in figure 9: the contours show the 3, 4, 5, 7, 10, 15, and 20σ levels. Each row shows our Hercules pointings arranged from East to West, with the middle panel roughly centered on the position of Hercules. The top row shows contour plots after smoothing the data by 2arcmin. The middle row is smoothed by 1.5arcmin, and the bottom row is smoothed by 1arcmin.
Nomenclature Notes: Stars are <[SOW2009] NNNNN> in Simbad in table 2 or <[SOW2009] F NNNNN> in table 3. History: From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 22-Nov-2011
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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