J/MNRAS/412/1539 Ages of stars in dwarf galaxies (Bastian+, 2011)
The evolution of stellar structures in dwarf galaxies.
Bastian N., Weisz D.R., Skillman E.D., McQuinn K.B.W., Dolphin A.E.,
Gutermuth R.A., Cannon J.M., Ercolano B., Gieles M., Kennicutt R.C.,
Walter F.
<Mon. Not. R. Astron. Soc., 412, 1539-1551 (2011)>
=2011MNRAS.412.1539B 2011MNRAS.412.1539B
ADC_Keywords: Galaxies, photometry ; Stars, ages
Keywords: galaxies: dwarf - galaxies: individual: DDO 165 -
galaxies: individual: Holmberg II - galaxies: individual: IC 2574 -
galaxies: individual: NGC 784 - galaxies: individual: NGC 2366
Abstract:
We present a study of the variation of spatial structure of stellar
populations within dwarf galaxies as a function of the population age.
We use deep Hubble Space Telescope/Advanced Camera for Surveys
imaging of nearby dwarf galaxies in order to resolve individual stars
and create composite colour-magnitude diagrams (CMDs) for each
galaxy. Using the obtained CMDs, we select blue helium burning stars,
which can be unambiguously age-dated by comparing the absolute
magnitude of individual stars with stellar isochrones. Additionally,
we select a very young (~<10Myr) population of OB stars for a subset
of the galaxies based on the tip of the young main sequence. By
selecting stars in different age ranges, we can then study how the
spatial distribution of these stars evolves with time.
Description:
Observations of all galaxies were taken with the Advanced Camera for
Surveys (ACS) aboard HST. DDO 165, Holmberg II, NGC 2366 and IC 2574
were observed in the F555W and F814W filters as part of a
survey of the M81 group dwarf galaxies
(GO-10605 - Weisz et al., 2008ApJ...689..160W 2008ApJ...689..160W; also GO-9755,
PI Walter, was used for IC 2574), while NGC 4068
(GO-9771 - Karachentsev & Kashibadze, 2006Ap.....49....3K 2006Ap.....49....3K) and
NGC 784 (GO-10210 - Tully et al., 2006AJ....132..729T 2006AJ....132..729T) were both
observed in the F606W and F814W filters. The data we use in this paper
have been processed as described in Weisz et al. (2008ApJ...689..160W 2008ApJ...689..160W)
and McQuinn et al. (2010ApJ...721..297M 2010ApJ...721..297M).
Objects:
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RA (2000) DE Designation(s)
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13 06 24.9 +67 42 25 DDO 165 = UGC 8201
08 19 05.0 +70 43 12 Holmberg II = UGC 4305
10 28 23.5 +68 24 44 IC 2574 = DDO 81
07 28 51.9 +69 12 31 NGC 2366 = DDO 42
12 04 02.3 +52 35 19 NGC 4068 = UGC 7047
02 01 16.9 +28 50 14 NGC 784 = UGC 1501
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 48 100437 The position, age and estimated age error for all
Blue-He-burning (BHeB) and young stars in our sample
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 11 A11 --- Gal Galaxy name (1)
13- 18 I6 --- Star Star sequential number within the galaxy
19- 20 A2 --- n_Star [MS ] MS for stars selected as young main
sequence stars
22- 28 F7.2 pix Xpos X position
30- 36 F7.2 pix Ypos Y position
38- 42 F5.1 Myr Age Age
44- 48 F5.1 Myr e_Age ?=- rms uncertainty on Age
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Note (1): the galaxies studied are DDO 165, Holmberg II, IC 2574, NGC 2366,
NGC 4068 and NGC 784.
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(End) Patricia Vannier [CDS] 27-Oct-2011