J/ApJ/764/73 HST VI photometry of HD 97950 cluster members stars (Pang+, 2013)
On the origin of mass segregation in NGC 3603.
Pang X., Grebel E.K., Allison R.J., Goodwin S.P., Altmann M., Harbeck D.,
Moffat A.F.J., Drissen L.
<Astrophys. J., 764, 73 (2013)>
=2013ApJ...764...73P 2013ApJ...764...73P
ADC_Keywords: Associations, stellar ; Clusters, open ; Photometry, HST ;
Proper motions
Keywords: ISM: individual: NGC 3603; stars: pre-main sequence;
open clusters and associations: individual: HD 97950;
stars: kinematics and dynamics;
stars: luminosity function, mass function; stars: massive
Abstract:
We present deep Hubble Space Telescope/Wide Field and Planetary Camera
2 photometry of the young HD 97950 star cluster in the giant H II
region NGC 3603. The data were obtained in 1997 and 2007 permitting us
to derive membership based on proper motions of the stars. Our data
are consistent with an age of 1 Myr for the HD 97950 cluster. A
possible age spread, if present in the cluster, appears to be small.
The global slope of the incompleteness-corrected mass function for
member stars within 60" is Γ=-0.88±0.15, which is flatter than
the value of a Salpeter slope of -1.35. The radially varying mass
function shows pronounced mass segregation ranging from slopes of
-0.26 ±0.32 in the inner 5" to -0.94±0.36 in the outermost annulus
(40"-60"). Stars more massive than 50M☉ are found only in the
cluster center. The Λ minimum spanning tree technique confirms
significant mass segregation down to 30M☉. The dependence of
Λ on mass, i.e., that high-mass stars are more segregated than
low-mass stars, and the (weak) dependence of the velocity dispersion
on stellar mass might imply that the mass segregation is dynamical in
origin. While primordial segregation cannot be excluded, the
properties of the mass segregation indicate that dynamical mass
segregation may have been the dominant process for segregation of
high-mass stars.
Description:
For our analysis of the HD 97950 cluster in NGC 3603 we used deep
imaging data obtained with HST/WFPC2 in the F547M and F814W filters.
The first observations were carried out in 1997 July (program GO 6763,
PI: Drissen). The Planetary Camera (PC) chip was centered on the
cluster. The second data set was obtained in 2007 September (program
GO 11193, PI: Brandner) in F555W and F814W filters. The 10 year epoch
difference between the first and the second data set permits us to
infer cluster membership using proper motions.
Preliminary results of this analysis were presented by Pang et al.
(2010IAUS..266...24P 2010IAUS..266...24P). Rochau et al. (2010ApJ...716L..90R 2010ApJ...716L..90R) published a
proper motion study of the same data set.
Objects:
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RA (ICRS) DE Designation(s)
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11 15 07.35 -61 15 38.5 HD 97950 = NAME NGC 3603 YOUNG CLUSTER
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 53 411 The VI photometry and relative proper motions of
the member stars on the PC chip of WFPC2
table3.dat 53 68 The VI photometry and relative proper motions of
the member stars on the WFC2 chip of WFPC2
table4.dat 53 33 The VI photometry and relative proper motions of
the member stars on the WFC4 chip of WFPC2
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See also:
B/hst : HST Archived Exposures Catalog (STScI, 2007)
J/A+A/548/A97 : Catalogue of variable stars in open clusters (Zejda+, 2012)
J/ApJ/675/1319 : Infrared photometry of NGC 3603 (Harayama+, 2008)
J/MNRAS/368/253 : Faint emission lines in NGC 3603 (Garcia-Rojas+, 2006)
J/A+A/446/949 : Open clusters proper motions based on UCAC2 (Dias+, 2006)
J/AJ/127/1014 : CCD UBVRIHa photometry in NGC 3603 (Sung+, 2004)
J/AZh/80/8 : Proper motions of open star clusters (Loktin+, 2003)
J/MNRAS/335/233 : Integrated Spectra of Open Clusters (Piatti+, 2002)
J/MNRAS/327/23 : CCD UBVRI photometry of 7 open star clusters (Sagar+, 2001)
J/PAZh/25/10 : Young open clusters space-age distribution (Dambis, 1999)
Byte-by-byte Description of file: table[234].dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- Seq Star running sequence number
5- 10 F6.2 pix Xpos X pixel coordinate from the 2007 WFPC2 data
12- 17 F6.2 pix Ypos Y pixel coordinate from the 2007 WFPC2 data
19- 23 F5.2 mag Vmag [11.9/23.7] V band magnitude from the 1997
WFPC2 data
25- 29 F5.2 mag Imag [10.3/21.2] I band magnitude from the 1997
WFPC2 data
31- 35 F5.2 arcsec Rad [0.9/59.4] Cluster-centric distance
37- 44 F8.5 mas/yr pmRA [-1.2/1.3] Proper motion along X pixel direction
46- 53 F8.5 mas/yr pmDE [-1.4/1.4] Proper motion along Y pixel direction
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 27-Oct-2014