We present the first V, B-V color-magnitude diagram of the Leo IV dwarf spheroidal galaxy, a faint Milky Way satellite recently discovered by the Sloan Digital Sky Survey. We have obtained B,V time-series photometry reaching about half a magnitude below the Leo IV turnoff, which we detect at V= 24.7 mag, and have performed the first study of the variable star population. We have identified three RR Lyrae stars (all fundamental-mode pulsators, RRab) and one SX Phoenicis variable in the galaxy. In the period-amplitude diagram the Leo IV RR Lyrae stars are located close to the loci of Oosterhoff type I systems and the evolved fundamental-mode RR Lyrae stars in the Galactic globular cluster M3. However, their mean pulsation period, $<P{\rm ab}>$=0.655 days, would suggest an Oosterhoff type II classification for this galaxy. The RR Lyrae stars trace very well the galaxy's horizontal branch, setting its average magnitude at $<V_{\rm RR}>= 21.48 \pm 0.03$ mag (standard deviation of the mean). This leads to a distance modulus of $\mu_{0}=20.94 \pm 0.07$ mag, corresponding to a distance of $154 \pm 5$ kpc, by adopting for the Leo IV dSph a reddening $E(B-V) = 0.04 \pm 0.01$ mag and a metallicity of [Fe/H] = -2.31 $\pm$ 0.10. Comment: 14 pages, 4 figures, accepted for publication on The Astrophysical Journal Letters
All content in this area was uploaded by M. Dall'Ora
Content may be subject to copyright.
A preview of the PDF is not available
... In this paper we focus on two of these new ultra-faint dwarfs, namely Leo IV ( Belokurov et al., 2007) and Leo V ( Belokurov et al., 2008). Their properties are studied by many authors: for Leo IV: ( Moretti et al., 2009;Simon et al., 2010;Sand et al., 2010) and for Leo V: ( Walker et al., 2009a,b). Both galaxies are very close to each other in radial distance (22 kpc) ( Moretti et al., 2009;De Jong et al., 2010) and also in projected distance on the sky. ...
... Their properties are studied by many authors: for Leo IV: ( Moretti et al., 2009;Simon et al., 2010;Sand et al., 2010) and for Leo V: ( Walker et al., 2009a,b). Both galaxies are very close to each other in radial distance (22 kpc) ( Moretti et al., 2009;De Jong et al., 2010) and also in projected distance on the sky. Their relative radial velocity differs only by about 50 km s −1. ...
We present data collected using the camera PISCES coupled with the Firt Light
Adaptive Optics (FLAO) mounted at the Large Binocular Telescope (LBT). The
images were collected using two natural guide stars with an apparent magnitude
of R<13 mag. During these observations the seeing was on average ~0.9". The AO
performed very well: the images display a mean FWHM of 0.05 arcsec and of 0.06
arcsec in the J- and in the Ks-band, respectively. The Strehl ratio on the
quoted images reaches 13-30% (J) and 50-65% (Ks), in the off and in the central
pointings respectively. On the basis of this sample we have reached a J-band
limiting magnitude of ~22.5 mag and the deepest Ks-band limiting magnitude ever
obtained in a crowded stellar field: Ks~23 mag.
J-band images display a complex change in the shape of the PSF when moving at
larger radial distances from the natural guide star. In particular, the stellar
images become more elongated in approaching the corners of the J-band images
whereas the Ks-band images are more uniform. We discuss in detail the strategy
used to perform accurate and deep photometry in these very challenging images.
In particular we will focus our attention on the use of an updated version of
ROMAFOT based on asymmetric and analytical Point Spread Functions.
The quality of the photometry allowed us to properly identify a feature that
clearly shows up in NIR bands: the main sequence knee (MSK). The MSK is
independent of the evolutionary age, therefore the difference in magnitude with
the canonical clock to constrain the cluster age, the main sequence turn off
(MSTO), provides an estimate of the absolute age of the cluster. The key
advantage of this new approach is that the error decreases by a factor of two
when compared with the classical one. Combining ground-based Ks with space
F606W photometry, we estimate the absolute age of M15 to be 13.70+-0.80 Gyr.
Jan 2006
897
V Belokurov
Belokurov, V., et al. 2006, ApJ, 647, L111
Belokurov, V., et al. 2007, ApJ, 654, 897
Jan 2008
83
V Belokurov
Belokurov, V., et al. 2008, ApJ, 686, L83
Belokurov, V., et al. 2009, arXiv:0903.0818
Jan 1996
393
E Bertin
S Arnouts
Bertin, E., & Arnouts, S. 1996, A&AS, 117, 393
Jan 2005
267
C Cacciari
T M Corwin
B W Carney
Cacciari, C., Corwin, T. M., & Carney, B. W. 2005, AJ, 129, 267
Jan 2007
1020
D Carollo
Carollo, D., et al. 2007, Nature, 450, 1020
Jan 2009
261
M Catelan
Catelan, M. 2009, Ap&SS, 320, 261
Jan 2000
2579
C M Clement
J Rowe
Clement, C. M., & Rowe, J. 2000, AJ, 120, 2579
Jan 2003
1309
G Clementini
R G Gratton
A Bragaglia
E Carretta
Di Fabrizio
Clementini, G., Gratton, R. G., Bragaglia, A., Carretta, E., Di Fabrizio, L., & Maio, M.
2003, AJ, 125, 1309