J/ApJ/741/86 XRBs and star clusters in NGC 4449 (Rangelov+, 2011)
The connection between X-ray binaries and star clusters in NGC 4449.
Rangelov B., Prestwich A.H., Chandar R.
<Astrophys. J., 741, 86 (2011)>
=2011ApJ...741...86R 2011ApJ...741...86R
ADC_Keywords: Clusters, globular ; Binaries, X-ray ; Photometry, HST
Keywords: binaries: close - galaxies: individual (NGC 4449) -
galaxies: star clusters: general - stars: evolution
Abstract:
We present 23 candidate X-ray binaries with luminosities down to
1.8x1036erg/s, in the nearby starburst galaxy NGC 4449, from
observations totaling 105ks taken with the ACIS-S instrument on the
Chandra Space Telescope. We determine count rates, luminosities, and
colors for each source, and perform spectral fits for sources with
sufficient counts. We also compile a new catalog of 129 compact star
clusters in NGC 4449 from high-resolution, multi-band optical images
taken with the Hubble Space Telescope, doubling the number of clusters
known in this galaxy. The UBVI, Hα luminosities of each cluster
are compared with predictions from stellar evolution models to
estimate their ages and masses. We find strong evidence for a
population of very young massive, black hole binaries, which comprise
nearly 50% of the detected X-ray binaries in NGC 4449. Approximately a
third of these remain within their parent star clusters, which formed
τ≤6-8Myr ago, while others have likely been ejected from their
parent clusters. We also find evidence for a population of somewhat
older X-ray binaries, including both supergiant and Be-binaries, which
appear to be associated with somewhat older τ∼100-400Myr star
clusters, and one X-ray binary in an ancient (τ∼10Gyr) globular
cluster. Our results suggest that detailed information on star
clusters can significantly improve constraints on X-ray binary
populations in star-forming galaxies.
Description:
We use three sets of archival Chandra observations of NGC 4449,
with integration times of 30ks (ObsID: 2031, PI: Heckman), 15ks
(ObsID: 10125. PI: Long), and 60ks (ObsID: 10875, PI: Long), to detect
X-ray point sources in NGC 4449. The data were taken with the Advanced
CCD Imaging Spectrometer (ACIS) instrument on the Chandra telescope on
2001 February 4 in "faint" mode (ObsID: 2031), and on 2010 March 4
and 7 in "vfaint" mode (ObsIDs: 10125 and 10875).
ACS/WFC imaging of two positions within NGC 4449 was taken in the
F435W (∼B), F555W (∼V band), F814W (∼I band), and the F658N (Hα)
filters on 2005 November 10-11 (Proposal ID GO: 10585, PI: Aloisi). We
downloaded the ACS data from the Hubble Legacy Archive (HLA).
We also use available F336W (∼U) band imaging of two pointings
within NGC 4449, taken with the WFPC2 camera (Proposal ID GO: 6716,
PI: Stecher).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 44 24 X-ray source catalog (23 X-ray binary candidates
and one supernova remnant candidate)
table5.dat 47 129 Star cluster catalog
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See also:
B/chandra : The Chandra Archive Log (CXC, 1999-2012)
B/hst : HST Archived Exposures Catalog (STScI, 2007)
J/AJ/141/113 : HII regions of M51 and NGC 4449 (Gutierrez+, 2011)
J/ApJS/192/10 : Chandra ACIS survey in 383 nearby galaxies. I. (Liu, 2011)
J/AJ/137/3869 : Radio SNRs in 4 irregular galaxies (Chomiuk+, 2009)
J/AZh/85/794 : UBVRHα photometry on 5 galaxies (Gusev+, 2008)
J/ApJ/664/458 : Spectral fit of ULX sources (Devi+, 2007)
J/ApJ/649/730 : ULX population in nearby galaxies from XMM (Winter+, 2006)
J/ApJS/157/59 : Ultraluminous X-ray sources in nearby galaxies (Liu+, 2005)
J/ApJ/602/231 : Chandra X-ray point sources in nearby gal. (Colbert+, 2004)
J/AJ/124/3157 : Velocities in NGC 4449 (Valdez-Gutierrez+, 2002)
J/A+AS/139/491 : BVI photometry of nearby galaxies (Makarova+, 1999)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 3 A3 --- ID [X0-9 ] X-ray source identification
(<[RPC2011] XNN> in Simbad)
4 A1 --- f_ID [b] b = Supernova remnant
6- 14 F9.5 deg RAdeg Right ascension in decimal degrees (J2000)
16- 23 F8.5 deg DEdeg Declination in decimal degrees (J2000)
25- 29 F5.2 --- H1 "Soft" color (1)
31- 35 F5.2 --- H2 "Hard" color (1)
37- 44 E8.3 10-7W LX X-ray (0.3-8keV) luminosity in erg/s (2)
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Note (1): We calculate two X-ray colors, a "soft" color defined as
H1=(M-S)/T and a "hard" color defined as H2=(H-M)/T, where S, M, and
H are the total counts measured in the soft (0.3-1keV), medium
(1-2keV), and hard (2-8keV) bands (Prestwich et al.
2003ApJ...595..719P 2003ApJ...595..719P), and T is the total number of counts in all
three bands.
Note (2): X-ray luminosities (0.3-8keV range) are derived by fitting a power law
(Γ=1.5) to the data. An assumed Galactic nH=1.5x1020cm-2
is applied.
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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 [1/129] Index number (<[RPC2011] NNN> in Simbad)
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 U-B The HST (U-B) color index
35- 40 F6.3 mag V-I The HST (V-I) color index
42- 46 F5.2 [yr] logA [6/10.27] Log of the cluster age (1)
47 A1 --- --- [0]
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Note (1): Typical uncertainties are approximately ±0.3 in logA.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 21-Feb-2013