J/ApJ/718/530 Leo IV g- and r-band photometry (Sand+, 2010)
A deeper look at Leo IV: star formation history and extended structure.
Sand D.J., Seth A., Olszewski E.W., Willman B., Zaritsky D.,
Kallivayalil N.
<Astrophys. J., 718, 530-542 (2010)>
=2010ApJ...718..530S 2010ApJ...718..530S
ADC_Keywords: Photometry, SDSS ; Galaxies, nearby ; Extinction ;
Stellar distribution
Keywords: galaxies: dwarf - Local Group
Abstract:
We present MMT/Megacam imaging of the Leo IV dwarf galaxy in order to
investigate its structure and star formation history, and to search
for signs of association with the recently discovered Leo V satellite.
Based on parameterized fits, we find that Leo IV is round, with
ε<0.23 (at the 68% confidence limit) and a half-light radius
of rh∼130pc. Additionally, we perform a thorough search for extended
structures in the plane of the sky and along the line of sight. We
derive our surface brightness detection limit by implanting fake
structures into our catalog with stellar populations identical to that
of Leo IV. We show that we are sensitive to stream-like structures
with surface brightness µr≲29.6mag/arcsec2, and at this limit
we find no stellar bridge between Leo IV (out to a radius of ∼0.5kpc)
and the recently discovered, nearby satellite Leo V. Using the
color-magnitude fitting package StarFISH, we determine that Leo IV is
consistent with a single age (∼14Gyr), single metallicity
([Fe/H]~-2.3) stellar population, although we cannot rule out a
significant spread in these values. We derive a luminosity of
MV=-5.5±0.3. Studying both the spatial distribution and frequency
of Leo IV's "blue plume" stars reveals evidence for a young (∼2Gyr)
stellar population which makes up ∼2% of its stellar mass.
Description:
We observed Leo IV on 2009 April 21 (UT) with Megacam on the MMT. We
obtained 5250s dithered exposures in g and in r in clear conditions
with 0.9" seeing. Precise astrometric solutions for each science
exposure were derived using the Sloan Digital Sky Survey Data
Release 6 (SDSS-DR6).
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 61 25282 Leo IV photometry
--------------------------------------------------------------------------------
See also:
II/294 : The SDSS Photometric Catalog, Release 7 (Adelman-McCarthy+, 2009)
J/ApJ/710/1664 : BV photometry in Leo IV and Leo V dSphs (de Jong+, 2010)
J/ApJS/191/352 : Abundances in stars of Milky Way dwarf satellites (Kirby+,
2010)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 I5 --- [SSO2010] [0/25281] Star index 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 gmag The g band magnitude; uncorrected for extinction
32- 35 F4.2 mag e_gmag Uncertainty in gmag
37- 40 F4.2 mag Ag Galactic extinction value in g band
42- 46 F5.2 mag rmag The r band magnitude; uncorrected for extinction
48- 51 F4.2 mag e_rmag Uncertainty in rmag
53- 56 F4.2 mag Ar Galactic extinction value in r band
58- 61 A4 --- Ref Photometry source; SDSS or MMT
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 07-Jun-2012