2012ApJ...756..108C

Query : 2012ApJ...756..108C

2012ApJ...756..108C - Astrophys. J., 756, 108 (2012/September-2)

Variability and star formation in Leo T, the lowest luminosity star-forming galaxy known today.

CLEMENTINI G., CIGNONI M., CONTRERAS RAMOS R., FEDERICI L., RIPEPI V., MARCONI M., TOSI M. and MUSELLA I.

Abstract (from CDS):

We present results from the first combined study of variable stars and star formation history (SFH) of the Milky Way "ultra-faint" dwarf (UFD) galaxy Leo T, based on F606W and F814W multi-epoch archive observations obtained with the Wide Field Planetary Camera 2 on board the Hubble Space Telescope. We have detected 14 variable stars in the galaxy. They include one fundamental-mode RR Lyrae star and 11 Anomalous Cepheids with periods shorter than 1 day, thus suggesting the occurrence of multiple star formation episodes in this UFD, of which one about 10 Gyr ago produced the RR Lyrae star. A new estimate of the distance to Leo T of 409+29_- 27_ kpc (distance modulus of 23.06 ±0.15 mag) was derived from the galaxy's RR Lyrae star. Our V, V - I color-magnitude diagram (CMD) of Leo T reaches V ∼ 29 mag and shows features typical of a galaxy in transition between dwarf irregular and dwarf spheroidal types. A quantitative analysis of the SFH, based on the comparison of the observed V, V - I CMD with the expected distribution of stars for different evolutionary scenarios, confirms that Leo T has a complex SFH dominated by two enhanced periods about 1.5 and 9 Gyr ago, respectively. The distribution of stars and gas shows that the galaxy has a fairly asymmetric structure.

Abstract Copyright: ∼

Journal keyword(s): galaxies: dwarf - galaxies: individual: Leo T - galaxies: stellar content - stars: formation - stars: variables: Cepheids - stars: variables: RR Lyrae

VizieR on-line data: <Available at CDS (J/ApJ/756/108): table2.dat table3.dat>

Nomenclature: Table 2: [CCC2012] VNN (Nos V1-V14)

Simbad objects: 37

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Number of rows : 37
N Identifier Otype ICRS (J2000)
RA 		ICRS (J2000)
DEC 		Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2024 		#notes
1 M 31 AGN 00 42 44.330 +41 16 07.50 4.86 4.36 3.44     ~ 12650 1
2 NAME Pisces I G 01 03 56.6 +21 53 41   16.18 14.3     ~ 387 0
3 IC 1613 GiC 01 04 48.4071 +02 07 10.185   10.42 10.01 9.77   ~ 1236 2
4 NAME Phoenix Dwarf Galaxy Sy1 01 51 06.3 -44 26 41   13.48 13.2 12.69   ~ 533 2
5 ACO S 373 ClG 03 38 29.4 -35 27 08           ~ 1827 0
6 NAME LMC G 05 23 34.6 -69 45 22     0.4     ~ 17434 0
7 NAME Carina dSph G 06 41 36.7 -50 57 58   22.14 11.0 19.47   ~ 1125 0
8 NAME UMa II Galaxy G 08 51 30.0 +63 07 48     13.3     ~ 374 0
9 [CCC2012] V10 V* 09 34 50.082 +17 02 45.07     22.55   22.14 ~ 1 0
10 [CCC2012] V9 V* 09 34 50.38 +17 02 37.4     22.64   22.14 ~ 1 0
11 [CCC2012] V14 V* 09 34 50.548 +17 01 45.66     22.53   22.00 ~ 1 0
12 [CCC2012] V5 V* 09 34 51.262 +17 02 49.90     22.54   22.03 ~ 1 0
13 [CCC2012] V3 V* 09 34 52.557 +17 02 42.04     22.41   22.01 ~ 1 0
14 [CCC2012] V8 V* 09 34 52.591 +17 02 19.76     22.74   22.18 ~ 1 0
15 [CCC2012] V7 V* 09 34 52.980 +17 02 26.21     22.57   22.13 ~ 1 0
16 [CCC2012] V1 V* 09 34 53.314 +17 03 06.19     22.76   22.11 ~ 1 0
17 [CCC2012] V2 V* 09 34 53.363 +17 02 49.77     22.80   22.21 ~ 1 0
18 NAME Leo T G 09 34 53.4 +17 03 05     15.1     ~ 391 0
19 [CCC2012] V4 V* 09 34 54.148 +17 02 34.65     22.59   22.07 ~ 1 0
20 [CCC2012] V6 RR* 09 34 55.63 +17 02 56.5     23.59   23.13 ~ 1 0
21 [CCC2012] V11 V* 09 34 57.225 +17 03 11.72     22.59   21.93 ~ 1 0
22 [CCC2012] V12 V* 09 34 57.241 +17 02 25.05     22.86   22.44 ~ 1 0
23 [CCC2012] V13 V* 09 34 58.518 +17 02 56.71     22.65   22.16 ~ 1 0
24 NAME Segue 1 G 10 07 03.2 +16 04 25     15.3     ~ 465 1
25 Z 64-73 G 10 08 28.12 +12 18 23.4   11.3 10.0     ~ 1208 1
26 NAME Leo IV Dwarf Galaxy G 11 32 57.0 -00 32 00     15.1     ~ 383 1
27 NAME Virgo Cluster ClG 12 26 32.1 +12 43 24           ~ 6645 0
28 M 68 GlC 12 39 27.98 -26 44 38.6     7.96     ~ 997 0
29 NAME CVn II Dwarf A GiC 12 56 18.083 +34 39 24.31   17       ~ 28 0
30 NAME Centaurus A Sy2 13 25 27.61521044 -43 01 08.8050291   8.18 6.84 6.66   ~ 4486 3
31 NAME CVn I dSph G 13 28 03.5 +33 33 21     13.1     ~ 326 1
32 NAME Bootes II G 13 58 00.0 +12 51 00     15.4     ~ 241 0
33 NAME Bootes Dwarf Spheroidal Galaxy G 14 00 00.0 +14 30 00     12.8     ~ 437 0
34 NAME Hercules Dwarf Galaxy G 16 31 02.0 +12 47 30     14.0     ~ 345 1
35 M 92 GlC 17 17 07.39 +43 08 09.4     6.52     ~ 2116 0
36 M 15 GlC 21 29 58.33 +12 10 01.2           ~ 3140 0
37 NAME Local Group GrG ~ ~           ~ 8391 0

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