2008AJ....135..823D

Query : 2008AJ....135..823D

2008AJ....135..823D - Astron. J., 135, 823-835 (2008/March-0)

The initial cluster mass function of super star clusters in irregular and spiral galaxies.

DOWELL J.D., BUCKALEW B.A. and TAN J.C.

Abstract (from CDS):

The initial cluster mass function (ICMF) is a fundamental property of star formation in galaxies. To gauge its universality, we measure and compare the ICMFs in irregular and spiral galaxies. Our sample of irregular galaxies is based on 13 nearby galaxies selected from a volume-limited sample from the fifth data release of the Sloan Digital Sky Survey (SDSS), from which about 320 young (≤20 Myr), massive (≳3x104M☉) clusters or associations were selected using an automated source extraction routine. The extinctions, ages, and masses were determined by comparing their u'g'i'z' magnitudes to those generated from starburst models. Completeness corrections were performed using Monte Carlo simulations in which artificial clusters were inserted into each galaxy. Foreground stellar and background galactic contaminations were assessed by analyzing SDSS images of fields around the sample galaxies and found to be small. We analyzed three nearby spiral galaxies with SDSS data exactly in the same way to derive their ICMF based on a similar number of young, massive clusters as the irregular galaxy ICMF. We find that the ICMFs of irregular and spiral galaxies for masses >104.4M☉ are statistically indistinguishable. For clusters and associations more massive than 104.4M☉, the ICMF of the irregular galaxies is reasonably well fit by a power law with αM= 1.88±0.09. Similar results were obtained for the ICMF of the spiral galaxy sample but with αM = 1.75±0.06. We discuss the implications of our results on theories of star cluster formation, which appear to indicate that the power-law indices are independent of metallicity and galactic shear rate. We also examine the evolution of visual extinction, AV, with cluster age and find significant reduction in median extinction after ∼ 5–10 Myr by about 0.5 mag for clusters in both spiral and irregular galaxies. We discuss the implications of our results for theories of star cluster formation: the shape of the ICMF appears to be independent of metallicity and galactic shear rate.

Abstract Copyright: ∼

Journal keyword(s): galaxies: irregular - galaxies: spiral - galaxies: star clusters

VizieR on-line data: <Available at CDS (J/AJ/135/823): table1.dat table2.dat>

Nomenclature: Table 2: [DBT2008] NGC NNNN NNNN, [DBT2008] IC 3521 N, [DBT2008] UGC NNNN NN, [DBT2008] DDO NNNN NN, N=933.

Status at CDS : All or part of tables of objects could be ingested in SIMBAD with priority 2.

Simbad objects: 33

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Number of rows : 33
N Identifier Otype ICRS (J2000)
RA 		ICRS (J2000)
DEC 		Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2026 		#notes
1 NGC 20 GiG 00 09 32.6826129552 +33 18 31.469137380   14.5       ~ 34 0
2 NAME SMC G 00 52 38.0 -72 48 01   2.79 2.2     ~ 12317 1
3 SBSG 0335-052 AGN 03 37 44.06 -05 02 40.2     16.65     ~ 500 1
4 NGC 1569 rG 04 30 49.186 +64 50 52.52 11.72 11.86 11.03     ~ 1297 3
5 NGC 1705 Sy2 04 54 13.4661493464 -53 21 39.471592428 12.32 12.96 12.56 12.58 12.9 ~ 692 1
6 NAME LMC G 05 23 34.6 -69 45 22     0.4     ~ 19090 0
7 NAME Orion Nebula Cluster OpC 05 35.0 -05 29           ~ 2514 0
8 NGC 2552 EmG 08 19 20.5355420472 +50 00 34.590204468 13.44 13.00 12.56     ~ 284 1
9 MCG-04-21-005 AGN 08 36 15.190 -26 24 33.66 12.04 11.93 11.45 11.09 12.3 ~ 600 3
10 NGC 3310 AGN 10 38 45.85707 +53 30 11.8940   12.45 12.15     ~ 809 1
11 Z 242-46 bCG 11 33 29.12 +49 14 17.4 14.69 14.61 14.25 14.17   ~ 242 1
12 NGC 3738 AGN 11 35 48.982 +54 31 24.70   12.12 12.04 11.56   ~ 303 0
13 NGC 4038 EmG 12 01 53.002 -18 52 03.32   10.91   9.74 11.0 ~ 1364 1
14 NAME Antennae IG 12 01 53.170 -18 52 37.92           ~ 1749 0
15 NGC 4039 GiP 12 01 53.51 -18 53 10.3   11.08   9.77   ~ 1173 1
16 NGC 4190 LSB 12 13 44.765 +36 38 02.49 13.88 13.40 13.25 12.86   ~ 224 0
17 NGC 4228 SBG 12 15 39.174 +36 19 36.80 10.63 10.30 9.93 9.74   ~ 1017 1
18 Z 244-7 GiG 12 21 15.01 +45 48 40.8   14.8       ~ 123 2
19 NGC 4449 EmG 12 28 11.118 +44 05 36.81 10.11 9.98 9.64 9.45   ~ 1192 1
20 NGC 4485 GiP 12 30 31.113 +41 42 04.22 12.10 12.42 11.93 11.93   ~ 305 2
21 NGC 4490 GiG 12 30 34.5 +41 38 26 10.03 10.22 9.79     ~ 616 3
22 NAME Virgo Cluster ClG 12 30 47.8 +12 23 07           ~ 7107 0
23 IC 3521 GiG 12 34 39.5123938944 +07 09 36.681474564   14.2       ~ 148 0
24 NGC 4571 GiC 12 36 56.3722998960 +14 13 02.296534836   13.6       ~ 368 1
25 NGC 4656 GiP 12 43 57.6889089768 +32 10 13.345914504   10.96 10.52     ~ 385 3
26 NGC 4713 GiG 12 49 57.8802780576 +05 18 40.933127196   12.3       ~ 320 1
27 Z 316-9 AG? 13 06 24.85 +67 42 25.0 14.08 13.61 13.08 12.98   ~ 268 1
28 MCG+08-24-090 AG? 13 13 22.839 +46 19 21.71   17       ~ 135 1
29 Z 245-36 AG? 13 14 27.997 +45 55 11.14 13.63 13.26 13.02 12.81   ~ 297 0
30 NGC 5253 rG 13 39 55.990 -31 38 24.11 11.48 10.94 10.49 10.33 13.47 ~ 1421 4
31 M 101 GiP 14 03 12.583 +54 20 55.50   8.46 7.86 7.76   ~ 3138 2
32 IC 4662 bCG 17 47 09.192 -64 38 19.25   11.75 11.1 10.45   ~ 253 4
33 NAME Local Group GrG ~ ~           ~ 9325 0

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