J/ApJ/797/15 HST/WFC3 observations in 4 metal-poor GCs of Fornax (Larsen+, 2014)
Nitrogen abundances and multiple stellar populations in the globular clusters
of the Fornax dSph.
Larsen S.S., Brodie J.P., Grundahl F., Strader J.
<Astrophys. J., 797, 15 (2014)>
=2014ApJ...797...15L 2014ApJ...797...15L
ADC_Keywords: Photometry, HST ; Clusters, globular
Keywords: galaxies: star clusters: individual: (Fornax 1, Fornax 2, Fornax 3,
Fornax 5); Hertzsprung-Russell and C-M diagrams; stars: abundances
Abstract:
We use measurements of nitrogen abundances in red giants to search for
multiple stellar populations in the four most metal-poor globular
clusters (GCs) in the Fornax dwarf spheroidal galaxy (Fornax 1, 2, 3,
and 5). New imaging in the F343N filter, obtained with the Wide Field
Camera 3 on the Hubble Space Telescope, is combined with archival
F555W and F814W observations to determine the strength of the NH band
near 3370Å. After accounting for observational errors, the spread
in the F343N-F555W colors of red giants in the Fornax GCs is similar
to that in M15 and corresponds to an abundance range of
Δ[N/Fe]∼2dex, as observed also in several Galactic GCs. The
spread in F555W-F814W is, instead, fully accounted for by
observational errors. The stars with the reddest F343N-F555W colors
(indicative of N-enhanced composition) have more centrally
concentrated radial distributions in all four clusters, although the
difference is not highly statistically significant within any
individual cluster. From double-Gaussian fits to the color
distributions, we find roughly equal numbers of "N-normal" and
"N-enhanced" stars (formally ∼40% N-normal stars in Fornax 1, 3, and 5
and ∼60% in Fornax 2). We conclude that GC formation, in particular,
regarding the processes responsible for the origin of multiple stellar
populations, appears to have operated similarly in the Milky Way and
in the Fornax dSph. Combined with the high ratio of metal-poor GCs to
field stars in the Fornax dSph, this places an important constraint on
scenarios for the origin of multiple stellar populations in GCs.
Description:
We observed the four metal-poor GCs (Fornax 1, 2, 3, and 5) with the
HST/WFC3 F343N filter (program ID 13295; PI: S. Larsen). Each cluster
was observed for four orbits.
The WFC3 observations were combined with archival WFPC2 F555W and
F814W images (program ID 5917; PI: R. Zinn; Buonanno et al.
1998ApJ...501L..33B 1998ApJ...501L..33B).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 76 1227 Photometry for Fornax 1
table2.dat 76 5011 Photometry for Fornax 2
table3.dat 76 3283 Photometry for Fornax 3
table4.dat 76 3436 Photometry for Fornax 5
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See also:
B/hst : HST Archived Exposures Catalog (STScI, 2007)
VII/151 : Structure Parameters of Galactic Globular Clusters (Webbink 1985)
J/A+A/572/A82 : Abundances in outer parts of Fornax dSph (Hendricks+, 2014)
J/A+A/562/A24 : Cool carbon stars in the halo and Fornax dSph (Mauron+, 2014)
J/ApJ/772/82 : A catalog of globular cluster systems (Harris+, 2013)
J/ApJ/763/40 : UBVI phot. of GCs in the Fornax galaxy cluster (Kim+, 2013)
J/A+A/544/A73 : BVI photometry of Fornax dSph galaxy (de Boer+, 2012)
J/A+A/534/A136 : Halo red giants from the SEGUE survey (Martell+, 2011)
J/A+A/534/A9 : Synthetic spectra of galactic GCs (Sbordone+, 2011)
J/ApJS/193/1 : UBVRIJHK color-temperature calibration (Worthey+, 2011)
J/ApJ/705/1481 : Spectroscopy of stars in 6 GCs (Da Costa+, 2009)
J/A+A/505/117 : Abundances of red giants in 15 GCs (Carretta+, 2009)
J/ApJ/701/1323 : Variable stars in Fornax dSph. III. (Greco+, 2009)
J/ApJ/689/1031 : Heavy element abundances in giant stars (Yong+, 2008)
J/A+A/486/437 : CN and CH line strengths in 8 Galactic GlCl (Kayser+, 2008)
J/ApJ/681/197 : ACS Virgo Cluster Survey. XV (Peng+, 2008)
J/A+A/459/423 : VI and [Fe/H] of Fornax dSph RGB stars (Battaglia+, 2006)
J/MNRAS/345/747 : RR Lyrae in 4 Fornax globular clusters (Mackey+, 2003)
J/A+A/354/169 : Metal-poor field stars abundances (Gratton+, 2000)
J/AJ/118/1671 : Fornax cluster 4 VI photometry (Buonanno+, 1999)
J/A+AS/139/393 : Young Massive Star Clusters. II. (Larsen, 1999)
J/A+A/317/54 : Fornax cluster 1 and 3 photometry (Jorgensen+ 1997)
J/AJ/114/1471 : Fornax Globular 3 (Smith+ 1997)
J/AJ/111/1596 : BV photometry in Fornax globulars (Smith+ 1996)
J/A+AS/106/199 : B-band photometry in Fornax and Virgo (Caon+ 1994)
Byte-by-byte Description of file: table[1-4].dat
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Bytes Format Units Label Explanations
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1- 5 I5 --- ID [5/57575] Identification number (1)
7- 12 F6.2 pix Xpix X pixel coordinate in F555W image
14- 19 F6.2 pix Ypix Y pixel coordinate in F555W image
21- 26 F6.3 mag F555W [18.1/27.2] HST/WFPC2 F555W band magnitude
28- 32 F5.3 mag e_F555W [0.003/0.3] ALLFRAME error in F555Wmag
34- 38 F5.3 mag s_F555W [0.009/1.4] Weighted RMS deviation of
individual F555Wmag measurements
40- 45 F6.3 mag F814W [17.7/27.9] HST/WFPC2 F814W band magnitude
47- 51 F5.3 mag e_F814W [0.004/0.3] ALLFRAME error in F814Wmag
53- 57 F5.3 mag s_F814W [0.008/1.6] Weighted RMS deviation of
individual F814Wmag measurements
59- 64 F6.3 mag F343N [20.7/27.3] HST/WFC3 F343N band magnitude
66- 70 F5.3 mag e_F343N [0.009/0.4] ALLFRAME error in F343Nmag
72- 76 F5.3 mag s_F343N [0.008/2] Weighted RMS deviation of
individual F343Nmag measurements
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Note (1): IDs >50000 denote stars that were detected in the second
ALLFRAME iteration.
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History:
From electronic version of the journal
References:
Larsen et al. Paper II: M15. 2015ApJ...804...71L 2015ApJ...804...71L Cat. J/ApJ/804/71
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 05-Aug-2015