J/AJ/132/1361 RR Lyrae variables in M33 (Sarajedini+, 2006)
RR Lyrae variables in M33. I. Evidence for a field halo population.
Sarajedini A., Barker M.K., Geisler D., Harding P., Schommer R.
<Astron. J., 132, 1361-1371 (2006)>
=2006AJ....132.1361S 2006AJ....132.1361S
ADC_Keywords: Galaxies, nearby ; Stars, variable ; Photometry
Keywords: galaxies: individual (M33) - galaxies: spiral -
galaxies: stellar content - stars: variables: other
Abstract:
We present observations of RR Lyrae variables in the Local Group
late-type spiral galaxy M33. Using the Advanced Camera for Surveys
on the Hubble Space Telescope, we have identified 64 ab-type RR Lyrae
stars in M33. We have estimated reddenings for these stars based on
their minimum light V-I colors and metallicities based on their
periods. From the distributions of these properties, we conclude that
the RR Lyrae stars belong to two populations: one associated with the
halo of M33 and the other associated with its disk. Given that RR
Lyrae stars are produced by populations older than 10Gyr, this
suggests that not only does the field halo of M33 contain an old
component, but so does its disk. This is one of the best pieces of
evidence for the existence of a halo field component in M33. Using
a relation between RR Lyrae absolute magnitude and metallicity
(MV(RR)=0.23[Fe/H]+0.93), we estimate a mean distance modulus of
(m-M)0=24.67±0.08 for M33. This places M33 approximately 70kpc
beyond M31 in line-of-sight distance.
Description:
The images used in the present study were obtained with the HST using
the Advanced Camera for Surveys (ACS) as part of our GO-9873 program.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 75 72 RR Lyrae Properties
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See also:
J/AJ/121/870 : BVI photometry of Variables in M33 (Macri+, 2001)
J/AJ/121/2032 : Direct variables in M33A field (Mochejska+, 2001)
J/AJ/122/2477 : DIRECT variables in M33B field (Mochejska+, 2001)
J/MNRAS/371/1405 : Variables in M33 (Hartman+, 2006)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 3 A3 --- Field Field (1)
5- 8 A4 --- Inst Instrument (WFC1 or WFC2) (1)
10- 15 I6 --- [SBG2006] Identification number
18- 19 I2 h RAh Right ascension (J2000.0)
21- 22 I2 min RAm Right ascension (J2000.0)
24- 28 F5.2 s RAs Right ascension (J2000.0)
30 A1 --- DE- Declination sign (J2000.0)
31- 32 I2 deg DEd Declination (J2000.0)
34- 35 I2 arcmin DEm Declination (J2000.0)
37- 40 F4.1 arcsec DEs Declination (J2000.0)
42- 47 F6.3 mag Vmag V magnitude
49- 54 F6.3 mag Imag I magnitude
56- 60 F5.3 mag V-I V-I colour index
62- 66 F5.3 d Per Period
68- 72 F5.3 mag Iamp Amplitude in I band
74- 75 A2 --- VType RR Lyrae variable type
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Note (1): Fields are M9 WFC1, M9 WFC2, U49 WFC1 and U49 WFC2
Observing Log
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Field RA (J2000.0) DE PA Filter Exp. Time (s)
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U49 01 33 40 +30 47 59 316.59 F606W 1x2494, 3x2640
U49 01 33 40 +30 47 59 316.59 F814W 2x2494, 6x2640
M9 01 34 30 +30 38 13 239.45 F606W 1x2494, 3x2640
M9 01 34 30 +30 38 13 239.45 F814W 2x2494, 6x2640
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Note: PA: Position angle of V3 axis of HST in degrees.
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 25-Apr-2008