J/ApJ/743/149 Color-metallicity relations. II. M87 GCs (Yoon+, 2011)
Nonlinear color-metallicity relations of globular clusters.
II. A test on the nonlinearity scenario for color bimodality using the u-band
colors: the case of M87 (NGC 4486).
Yoon S.-J., Sohn S.T., Lee S.-Y., Kim H.-S., Cho J., Chung C.,
Blakeslee J.P.
<Astrophys. J., 743, 149 (2011)>
=2011ApJ...743..149Y 2011ApJ...743..149Y
ADC_Keywords: Clusters, globular ; Photometry, HST ; Galaxies, nearby
Keywords: galaxies: clusters: general - galaxies: formation -
galaxies: individual (M49, M60, M87) - stars: horizontal-branch
Abstract:
We here propose a new photometric technique to probe the possible
nonlinear nature of globular clusters (GCs) color-metallicity
relations (CMRs). In essence, a color distribution of GCs is a
"projected" distribution of their metallicities. Since the form of
CMRs hinges on which color is used, the shape of color distributions
varies depending significantly on the colors. Among other optical
colors, the u-band related colors (e.g., u-g and u-z) are
theoretically predicted to exhibit significantly less inflected CMRs
than other preferred CMRs (e.g., for g-z). As a case study, we
performed the Hubble Space Telescope (HST)/WFPC2 archival u-band
photometry for the M87 (NGC 4486) GC system with confirmed color
bimodality. We show that the u-band color distributions are
significantly different from that of g-z and consistent with our model
predictions. With more u-band measurements, this method will support
or rule out the nonlinear CMR scenario for the origin of GC color
bimodality with high confidence.
Description:
We have downloaded WFPC2 F336W (u-band) images from the HST archive.
The total exposure time is 28.8ks. These data were used by Jordan et
al. (2002ApJ...576L.113J 2002ApJ...576L.113J).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table5.dat 65 800 The u-, g-, and z-band magnitudes and their
observational errors for the M87 GCs
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See also:
B/hst : HST Archived Exposures Catalog (STScI, 2007)
J/ApJS/197/33 : The M87 globular cluster system (Strader+, 2011)
J/ApJ/703/42 : HST photometry of M87 globular clusters (Peng+, 2009)
J/ApJS/180/54 : GC candidates in ACS Virgo survey (Jordan+, 2009)
J/MNRAS/382/1947 : CT1 photometry in NGC 1399 and NGC 4486 (Forte+, 2007)
J/AJ/131/866 : Hot populations in M87 globular clusters (Sohn+, 2006)
J/ApJ/613/279 : ACS Virgo Cluster Survey. III. M87 (Jordan+, 2004)
J/ApJ/559/812 : Globular cluster system in M87 (Hanes+, 2001)
J/ApJ/513/733 : Globular cluster system in M87 (Kundu+, 1999)
J/AJ/115/1801 : VRI photometry of M87 globular clusters (Harris+ 1998)
J/AJ/106/493 : Globular clusters in M87 (Lee+, 1993)
J/ApJS/73/671 : M87 globular clusters BVI photometry (Couture+, 1990)
Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- Seq Globular cluster running sequence number
5- 15 F11.7 deg RAdeg Right Ascension in decimal degrees (J2000)
17- 26 F10.7 deg DEdeg Declination in decimal degrees (J2000)
28- 33 F6.3 mag umag The u (HST/WFPC2 F336W) band AB magnitude
35- 39 F5.3 mag e_umag Error in umag
41- 46 F6.3 mag gmag The g (HST/ACS F475W) band AB magnitude (1)
48- 52 F5.3 mag e_gmag Error in gmag (1)
54- 59 F6.3 mag zmag The z (HST/ACS) F850LP) band AB magnitude (1)
61- 65 F5.3 mag e_zmag Error in zmag (1)
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Note (1): Obtained from Jordan et al. (2009, Cat. J/ApJS/180/54).
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History:
From electronic version of the journal
References:
Blakeslee et al. Paper I. 2010ApJ...710...51B 2010ApJ...710...51B
Yoon et al. Paper II. 2011ApJ...743..150Y 2011ApJ...743..150Y
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 14-May-2013