J/ApJ/841/92 Young massive star clusters in 2 LEGUS galaxies (Ryon+, 2017)
Effective radii of young, massive star clusters in two LEGUS galaxies.
Ryon J.E., Gallagher J.S., Smith L.J., Adamo A., Calzetti D., Bright S.N.,
Cignoni M., Cook D.O., Dale D.A., Elmegreen B.E., Fumagalli M.,
Gouliermis D.A., Grasha K., Grebel E.K., Kim H., Messa M., Thilker D.,
Ubeda L.
<Astrophys. J., 841, 92 (2017)>
=2017ApJ...841...92R 2017ApJ...841...92R
ADC_Keywords: Galaxies, nearby ; Associations, stellar ; Stars, ages ;
Stars, masses
Keywords: galaxies: general; galaxies: individual (NGC 628, NGC 1313);
galaxies: star clusters: general
Abstract:
We present a study of the effective (half-light) radii and other
structural properties of a systematically selected sample of young,
massive star clusters (≥5x103M☉ and ≤200Myr) in two nearby
spiral galaxies, NGC 628 and NGC 1313. We use Hubble Space Telescope
(HST) WFC3/UVIS and archival ACS/WFC data obtained by the Legacy
Extragalactic UV Survey (LEGUS), an HST Treasury Program. We measure
effective radii with GALFIT, a two- dimensional image-fitting package,
and with a new technique to estimate effective radii from the
concentration index of observed clusters. The distribution of
effective radii from both techniques spans ∼0.5-10pc and peaks at
2-3pc for both galaxies. We find slight positive correlations between
effective radius and cluster age in both galaxies, but no significant
relationship between effective radius and galactocentric distance.
Clusters in NGC 1313 display a mild increase in effective radius with
cluster mass, but the trend disappears when the sample is divided into
age bins. We show that the vast majority of the clusters in both
galaxies are much older than their dynamical times, suggesting they
are gravitationally bound objects. We find that about half of the
clusters in NGC 628 are underfilling their Roche lobes, based on their
Jacobi radii. Our results suggest that the young, massive clusters in
NGC 628 and NGC 1313 are expanding, due to stellar mass loss or
two-body relaxation, and are not significantly influenced by the tidal
fields of their host galaxies.
Description:
The Legacy Extragalactic UV Survey (LEGUS; Calzetti+ 2015AJ....149...51C 2015AJ....149...51C)
is a Hubble Space Telescope (HST) Cycle 21 Treasury program, which
obtained imaging of 50 nearby galaxies (within ∼13Mpc) in five filters
with WFC3/UVIS and ACS/WFC.
Separate catalogs are produced for each pointing on the two galaxies:
NGC 628c (central pointing), NGC 628e (east pointing), NGC 1313e (east
pointing), and NGC 1313w (west pointing).
Objects:
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RA (ICRS) DE Designation(s) Dist (Mpc)
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01 36 41.77 +15 47 00.5 NGC 628 = M74 D=9.9
03 18 16.05 -66 29 53.7 NGC 1313 = LEDA 12286 D=4.4
----------------------------------------------------------------
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 107 320 Properties of young massive clusters (YMCs)
in NGC 628
table4.dat 107 195 Properties of young massive clusters (YMCs)
in NGC 1313
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See also:
J/A+AS/139/393 : Young Massive Star Clusters. II. (Larsen, 1999)
J/A+A/416/537 : UBVI & HST photom. of young stellar clusters (Larsen, 2004)
J/ApJS/161/304 : Star clusters in the MW & satellites (McLaughlin+, 2005)
J/AJ/131/2478 : M31 and M33 UBVRI photometry (Massey+, 2006)
J/ApJS/173/538 : XUV-Disk galaxies in the Local Universe (Thilker+, 2007)
J/AJ/138/1667 : HST survey of young clusters in M31. III. (Barmby+, 2009)
J/AJ/138/332 : LEDA CMD/tip of the red giant branch (Jacobs+, 2009)
J/A+A/501/949 : Star cluster properties in 5 spiral galaxies (Mora+, 2009)
J/MNRAS/401/1965 : Globular clusters in M104 (Harris+, 2010)
J/AJ/140/75 : Antennae galaxies (NGC4038/4039) revisited (Whitmore+, 2010)
J/A+A/529/A25 : Star cluster photom. in 5 nearby gal. (Silva-Villa+, 2011)
J/MNRAS/452/525 : M83 young star cluster light profiles (Ryon+, 2015)
J/ApJ/806/16 : CHemical Abundances of Spirals. I. NGC628 (Berg+, 2015)
J/ApJ/812/147 : Slug analysis of star clusters in NGC628+7793 (Krumholz+, 2015)
Byte-by-byte Description of file: table[34].dat
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Bytes Format Units Label Explanations
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1- 6 A6 --- ID Object identifier
8- 15 F8.5 deg RAdeg Right Ascension in decimal degrees (J2000)
17- 25 F9.5 deg DEdeg Declination in decimal degrees (J2000)
27- 31 F5.3 mag CI [1.3/2.3] Concentration index in magnitudes
33- 36 F4.2 --- eta [1/9.3]? Power-law slope of EFF light
profile (1)
38- 42 F5.2 --- e_eta [0.01/80]? Error in eta
44- 48 F5.2 [pc] logReffg [-0.6/15.5]? Log of half-light radius
from GALFIT
50- 53 F4.2 [pc] E_logReffg ? Positive error in log Reff from GALFIT
55- 59 F5.2 [pc] e_logReffg ? Negative error in log Reff from GALFIT
61- 65 F5.2 [pc] logReffc [-0.6/1.3] Log of half-light radius from CI
67- 70 F4.2 [pc] E_logReffc Positive error in log Reff from CI
72- 75 F4.2 [pc] e_logReffc Negative error in log Reff from CI
77- 80 F4.2 [yr] logAge [6/8.3] Log of age
82- 85 F4.2 [yr] E_logAge Positive error on log age
87- 90 F4.2 [yr] e_logAge Negative error on log age
92- 95 F4.2 [Msun] logMass [3.7/5.7] Log of mass
97-100 F4.2 [Msun] E_logMass Positive error on log mass
102-105 F4.2 [Msun] e_logMass Negative error on log mass
107 I1 --- fvis [1/2] Visual inspection class, mode (2)
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Note (1): The power-law index of the EFF light profile, η, describes the
slope of the wings of a star cluster's intensity profile.
The smallest possible value of η is artificially set to 1.0 by
GALFIT because a light profile with η<1.0 must, by definition,
contain an infinite amount of light.
See section 4.3 for further explanations.
Note (2): Class as follows:
1 = Compact and centrally concentrated with an FWHM more extended than that of
a star. Homogeneous in color.
2 = Slightly elongated or asymmetric light profile shapes with an FWHM more
extended than that of a star. Homogeneous in color.
See section 2 for further explanations.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 18-Jan-2018