J/ApJ/826/32 HST observations of star clusters in NGC 3256 (Mulia+, 2016)
Star cluster formation and destruction in the merging galaxy NGC 3256.
Mulia A.J., Chandar R., Whitmore B.C.
<Astrophys. J., 826, 32-32 (2016)>
=2016ApJ...826...32M 2016ApJ...826...32M (SIMBAD/NED BibCode)
ADC_Keywords: Photometry, HST ; Galaxies, optical ; Galaxies, nearby
Keywords: galaxies: star clusters: general; galaxies: star formation ;
galaxies: star clusters: individual: NGC 3256;
Abstract:
We use the Advanced Camera for Surveys on the Hubble Space Telescope
to study the rich population of young massive star clusters in the
main body of NGC 3256, a merging pair of galaxies with a high star
formation rate (SFR) and SFR per unit area (ΣSFR). These
clusters have luminosity and mass functions that follow power laws,
dN/dL∝Lα with α=-2.23±0.07, and
dN/dM∝Mβ with β=-1.86±0.34 for τ<10Myr
clusters, similar to those found in more quiescent galaxies. The age
distribution can be described by dN/dτ∝τγ, with
γ~-0.67±0.08 for clusters younger than about a few hundred
million years, with no obvious dependence on cluster mass. This is
consistent with a picture where ∼80% of the clusters are disrupted
each decade in time. We investigate the claim that galaxies with high
ΣSFR form clusters more efficiently than quiescent systems by
determining the fraction of stars in bound clusters (Γ) and the
CMF/SFR statistic (CMF is the cluster mass function) for NGC 3256 and
comparing the results with those for other galaxies. We find that the
CMF/SFR statistic for NGC 3256 agrees well with that found for
galaxies with ΣSFR and SFRs that are lower by 1-3 orders of
magnitude, but that estimates for Γ are only robust when the
same sets of assumptions are applied. Currently, Γ values
available in the literature have used different sets of assumptions,
making it more difficult to compare the results between galaxies.
Description:
Our observations come from the ACS on Hubble Space Telescope (HST).
NGC 3256 was observed using the filters F555W (∼V in the
Johnson-Cousins system; exposed for 2552s), FR656N (Hα; 2552s),
and F330W (∼U; 11358s) as part of the program GO-9735 (PI: Whitmore).
The V and U band images were taken in 2003 November using the Wide
Field Camera (WFC) and High Resolution Camera (HRC), respectively. The
Hα observations were taken in 2004 March. WFC observations using
F435W (∼B) and F814W (∼I) filters were taken in 2005 November as part
of program GO-10592 (PI: Evans) for 1320 and 760s, respectively.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 100 505 Catalog of candidate star clusters in NGC 3256
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See also:
J/ApJ/805/99 : Ages of star clusters in tidal tails of 3 gal. (Mulia+, 2015)
J/MNRAS/430/676 : Massive clusters in the LMC (Baumgardt+, 2013)
J/A+A/529/A25 : Photom. of star clusters in 5 galaxies (Silva-Villa+, 2011)
J/MNRAS/405/857 : Star clusters in NGC 3256 (Goddard+, 2010)
J/ApJ/706/599 : Hα and UV SFR in the local volume (Lee+, 2009)
J/AJ/138/1243 : The star formation history of the LMC (Harris+, 2009)
J/AJ/127/1531 : Star formation history of SMC (Harris+, 2004)
J/AJ/118/752 : BI photom. of NGC 3256 young globular clusters (Zepf+, 1999)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- Seq Running index number
5- 6 I2 h RAh [10] Hour of Right Ascension (J2000)
8- 9 I2 min RAm [27] Minute of Right Ascension (J2000)
11- 16 F6.3 s RAs [48.7/53.6] Second of Right Ascension (J2000)
18 A1 --- DE- [-] Sign of the Declination (J2000)
19- 20 I2 deg DEd [43] Degree of Declination (J2000)
22- 23 I2 arcmin DEm [53/54] Arcminute of Declination (J2000)
25- 29 F5.2 arcsec DEs Arcsecond of Declination (J2000)
31- 35 F5.2 mag Umag [15.9/26.3] Apparent U band magnitude
(HST/ACS F330W)
37- 40 F4.2 mag e_Umag [0/2.9] The 1σ uncertainty in Umag
42- 46 F5.2 mag Bmag [17/24] Apparent B band magnitude
(HST/WFC F435W)
48- 51 F4.2 mag e_Bmag [0/0.4] The 1σ uncertainty in Bmag
53- 57 F5.2 mag Vmag [17.4/23] Apparent V band magnitude
(HST/ACS F555W)
59- 62 F4.2 mag e_Vmag [0/0.4] The 1σ uncertainty in Vmag
64- 68 F5.2 mag Hamag [18/29] Apparent Hα band magnitude
(HST/ACS FR656N)
70- 74 F5.2 mag e_Hamag [0/24.1] The 1σ uncertainty in Hamag
76- 80 F5.2 mag Imag [15.8/23.2] Apparent I band magnitude
(HST/WFC F814W)
82- 85 F4.2 mag e_Imag [0/0.8] The 1σ uncertainty in Imag
87- 90 F4.2 [Msun] logM [3.9/7.3] Log cluster mass (1)
92- 95 F4.2 [yr] logtau [6.4/10] Log cluster age (1)
97-100 F4.2 mag E(B-V) [0/1.2] The (B-V) color excess (1)
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Note (1): Of best-fit SED model.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 20-Sep-2016