J/AJ/143/50 White dwarfs in 47 Tuc (NGC 104) with HST (Woodley+, 2012)
The spectral energy distributions of white dwarfs in 47 Tucanae: the distance
to the cluster.
Woodley K.A., Goldsbury R., Kalirai J.S., Richer H.B., Tremblay P.-E.,
Anderson J., Bergeron P., Dotter A., Esteves L., Fahlman G.G.,
Hansen B.M.S., Heyl J., Hurley J., Rich R.M., Shara M.M., Stetson P.B.
<Astron. J., 143, 50 (2012)>
=2012AJ....143...50W 2012AJ....143...50W
ADC_Keywords: Clusters, globular ; Stars, white dwarf ; Photometry, HST
Effective temperatures
Keywords: globular clusters: individual (47 Tucanae) - stars: distances -
white dwarfs
Abstract:
We present a new distance determination to the Galactic globular
cluster 47 Tucanae (47 Tuc, NGC 104) by fitting the spectral energy
distributions of its white dwarfs (WDs) to pure hydrogen atmosphere WD
models. Our photometric data set is obtained from a 121-orbit Hubble
Space Telescope program using the Wide Field Camera 3 UVIS/IR
channels, capturing F390W, F606W, F110W, and F160W images. These
images cover more than 60 arcmin2 and extend over a radial range of
5-13.7arcmin (6.5-17.9pc) within the globular cluster. Using a
likelihood analysis, we obtain a best-fitting unreddened distance
modulus of (m-M)o=13.36±0.02±0.06 corresponding to a
distance of 4.69±0.04±0.13kpc, where the first error is random and
the second is systematic. We also search the WD photometry for
infrared excess in the F160W filter, indicative of low-mass
companions, and find no convincing cases within our sample.
Description:
We obtained HST images of the Galactic globular cluster 47 Tuc in
cycle 17 (GO-11677, PI: H. Richer) with the Advanced Camera for
Surveys (ACS) and WFC3. Our observational design and reduction are
discussed in detail in Kalirai et al. (2012AJ....143...11K 2012AJ....143...11K).
Here we briefly review the WFC3 data set used in the present analysis:
we obtained 121 orbits covering >60arcmin2 and extending over 250deg
in azimuthal range of 47 Tuc. This covers a radial range of 5-13.7'
(6.5-17.9pc) within the globular cluster. For 61 orbits, we stared in
one field location in the cluster (stare field) obtaining 59 orbits of
IR images in F110W and F160W and 2 orbits of UVIS images in F390W and
F606W. We then swept out an arc around the cluster's center (swath
fields), using 5 orbits in each of our 12 additional fields, obtaining
F390W, F606W, F110W, and F160W images.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 107 59 Data on the selected white dwarfs
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See also:
B/hst : HST Archived Exposures Catalog (STScI, 2007)
J/A+A/537/A2 : 8.6um imaging of 47 Tuc (Momany+, 2012)
J/ApJS/166/249 : Stellar dynamics & PMs in 47 Tuc (McLaughlin+, 2006)
J/AJ/130/1693 : HST-ACS observations of 5 globular clusters (Brown+, 2005)
J/A+A/391/945 : HST photometry of 74 galactic GCs (Piotto+, 2002)
J/A+AS/144/5 : Nearby GCs photometric catalog (Rosenberg+, 2000)
J/A+AS/106/161 : VI photometry in NGC 6356 and 47 Tuc (Bica+ 1994)
J/ApJS/93/161 : CCD photometry of 6 globular clusters (Sarajedini+ 1994)
J/ApJS/85/293 : HST Observations of core of 47 Tuc (de Marchi+ 1993)
J/PASP/99/739 : BV photometry in 4 fields of 47 Tuc (Hesser+, 1987)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 5 A5 --- ID White dwarfs identification
<[WGK2012] WD NN> in Simbad
7- 14 A8 --- Field Field location in the cluster ("Stare" or
Swath 1-12 fields)
16- 17 I2 h RAh [0] Hour of right ascension (J2000)
19- 20 I2 min RAm [21/23] Minute of right ascension (J2000)
22- 27 F6.3 s RAs Second of right ascension (J2000)
29 A1 --- DE- [-] Sign of the declination (J2000)
30- 31 I2 deg DEd [71/72] Degree of declination (J2000)
33- 34 I2 arcmin DEm Arcminute of declination (J2000)
36- 40 F5.2 arcsec DEs Arcsecond of declination (J2000)
42- 47 F6.3 mag F390W [22.3/25.7] The HST/WFC3 F390W (UV) band
magnitude (Vega)
49- 54 F6.4 mag e_F390W Uncertainty on F390W
56- 61 F6.3 mag F606W [22.9/25.6] The HST/WFC3 F606W (optical) band
magnitude (Vega)
63- 68 F6.4 mag e_F606W Uncertainty on F606W
70- 75 F6.3 mag F110W [23.5/25.6] The HST/WFC3 F110W band (IR)
magnitude (Vega)
77- 82 F6.4 mag e_F110W Uncertainty on F110W
84- 89 F6.3 mag F160W [23.6/25.8] The HST/WFC3 F160W band (IR)
magnitude (Vega)
91- 96 F6.4 mag e_F160W Uncertainty on F160W
98-102 I5 K Teff [9600/32000] Effective temperature (1)
104-107 I4 K e_Teff Uncertainty on Teff
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Note (1): Effective temperature estimates assume a white dwarf mass
of 0.53M☉.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Sylvain Guehenneux [CDS] 22-Apr-2013