2013ApJ...763..101L

Query : 2013ApJ...763..101L

2013ApJ...763..101L - Astrophys. J., 763, 101 (2013/February-1)

The initial mass function of field OB stars in the Small Magellanic Cloud.

LAMB J.B., OEY M.S., GRAUS A.S., ADAMS F.C. and SEGURA-COX D.M.

Abstract (from CDS):

Some theories of star formation suggest massive stars may only form in clustered environments, which would create a deficit of massive stars in low-density environments. Observationally, Massey finds such a deficit in samples of the field population in the Small and Large Magellanic Clouds, with an initial mass function (IMF) slope of ΓIMF∼ 4. These IMF measurements represent some of the largest known deviations from the standard Salpeter IMF slope of ΓIMF= 1.35. Here, we carry out a comprehensive investigation of the mass function above 20 M☉ for the entire field population of the Small Magellanic Cloud (SMC), based on data from the Runaways and Isolated O Type Star Spectroscopic Survey of the SMC (RIOTS4). This is a spatially complete census of the entire field OB star population of the SMC obtained with the IMACS multi-object spectrograph and MIKE echelle spectrograph on the Magellan telescopes. Based on Monte Carlo simulations of the evolved present-day mass function, we find the slope of the field IMF above 20 M ☉ is ΓIMF= 2.3±0.4. We extend our IMF measurement to lower masses using BV photometry from the OGLE II survey. We use a statistical approach to generate a probability distribution for the mass of each star from the OGLE photometry, and we again find ΓIMF= 2.3±0.6 for stellar masses from 7 M☉ to 20 M☉. The discovery and removal of ten runaways in our RIOTS4 sample steepens the field IMF slope to ΓIMF= 2.8±0.5. We discuss the possible effects of binarity and star formation history on our results, and conclude that the steep field massive star IMF is most likely a real effect.

Abstract Copyright: ∼

Journal keyword(s): galaxies: stellar content - Magellanic Clouds - stars: early-type - stars: formation - stars: fundamental parameters - stars: luminosity function, mass function

VizieR on-line data: <Available at CDS (J/ApJ/763/101): table1.dat>

Simbad objects: 135

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Number of rows : 135
N Identifier Otype ICRS (J2000)
RA 		ICRS (J2000)
DEC 		Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2024 		#notes
1 OGLE SMC-SC2 97050 EB* 00 42 09.9208507704 -73 13 56.789709816   14.547 14.732   14.958 O8.5V 17 0
2 AzV 2b s*b 00 43 49.8604159944 -73 09 02.783039436 12.333 13.374 13.516   13.67 O9.5I 13 0
3 SK 4 * 00 44 57.0361455600 -73 59 13.398935892 12.78 13.61 13.78   17.20 O9.5Ib-II 13 0
4 2MASS J00451452-7335586 * 00 45 14.5182430680 -73 35 58.431942636   14.89 15.11     O8.5V 5 0
5 SK 10 s*b 00 46 42.1591125672 -73 24 55.494317340 11.903 12.984 13.176   13.35 O6.5I(f) 45 0
6 2MASS J00465615-7318570 * 00 46 56.1288272232 -73 18 57.002275332   14.30 14.46     O7.5V 6 0
7 2MASS J00480056-7334380 * 00 48 00.6021878376 -73 34 37.988222448   14.63 14.81     O7Vz 4 0
8 2MASS J00483085-7215596 * 00 48 30.8337127704 -72 15 59.792129280   14.80 15.01     O8.5V 6 0
9 2MASS J00484432-7259477 * 00 48 44.33 -72 59 47.7   14.12 14.13     O9V 5 0
10 LIN 121 Em* 00 48 45.4078668408 -73 48 16.236197964   14.47 14.6     O9V 6 0
11 AzV 43 * 00 48 47.8983993528 -72 46 24.890763828   13.76 13.88     O9II 18 0
12 OGLE SMC-SC5 26577 * 00 48 48.4621498824 -73 12 29.917346760 13.93 14.81 14.83   15.14 B0.5(IV) 8 0
13 SK 28 s*b 00 49 15.9428076984 -72 52 43.930468056 11.983 12.984 13.106   13.26 O9.5I 17 0
14 AzV 51 * 00 49 31.9993446528 -72 51 16.850696004 12.98 13.98 14.04   14.26 B0.5(IV) 15 0
15 SK 29 * 00 49 33.1991725872 -73 42 18.516841956 12.69 13.60 13.76   13.96 O8III-V 13 0
16 OGLE J004942.75-731717.7 Em* 00 49 42.7430092944 -73 17 18.162584196   14.338 14.453   14.404 O4-7V((f))e 7 0
17 AzV 57 * 00 49 54.3992757288 -72 24 37.732189968   14.11 14.25     O9III 9 0
18 AzV 58 * 00 49 57.8948279856 -72 51 54.784012932   14.11 14.29     B0.5III 14 0
19 SK 32 * 00 50 01.8667443096 -72 11 26.589718176 12.313 13.414 13.596   13.77 O6III((f)) 35 0
20 AzV 67 Em* 00 50 11.1185357880 -72 32 35.137328748 12.55 13.60 13.73   13.89 O9III 17 0
21 2MASS J00501902-7239179 * 00 50 19.0286403000 -72 39 17.930592252   14.03 14.15     B0.5III 6 0
22 OGLE SMC719.12.035620 El* 00 50 20.4688993248 -72 37 02.779964796   13.01 13.20   13.416 O9III 8 0
23 2MASS J00502559-7208030 * 00 50 25.5853083096 -72 08 03.228657504 13.95 14.16 14.76   14.86 O9.5Ib 7 0
24 LIN 147 Em* 00 50 26.0518985568 -72 12 10.378293480 12.84 13.83 14.02   14.15 B0-3(II)e 20 0
25 LHA 115-S 11 Em* 00 50 27.1936402248 -73 30 21.666149784   14.14 14.12 14.10 13.70 B0V 10 0
26 OGLE SMC-SC5 207949 * 00 50 39.9602502336 -72 59 43.462961196 13.51 14.50 14.63   14.76 O8V 7 0
27 LIN 169 Em* 00 50 59.5510842624 -73 32 03.847102044   14.64 14.6     O8III(f) 9 0
28 [M2002] SMC 19382 * 00 51 17.4908320608 -73 23 48.631366212   14.27 14.31     B0.2V 6 0
29 SK 46 s*b 00 51 23.1472439448 -72 07 20.916492744   12.49 12.59     B1.5Ia 25 0
30 2MASS J00515838-7315489 * 00 51 58.3987546968 -73 15 48.981777408   14.09 14.18     O7.5III((ff)) 6 0
31 OGLE SMC101.4 21947 EB* 00 51 58.9412921352 -72 16 38.508289140   14.96 15.10   15.425 O7Vz 9 0
32 LIN 195 Em* 00 52 05.9187723864 -73 04 25.362861672   13.969 13.904   13.624 O7.5-8.5Ve 10 0
33 2MASS J00520806-7332477 * 00 52 08.0839644072 -73 32 47.731207524   13.98 14.14     O9III 6 0
34 NAME SMC G 00 52 38.0 -72 48 01   2.79 2.2     ~ 11146 1
35 AzV 130 * 00 52 39.7428761448 -73 05 12.675098400 13.38 14.29 14.52   14.76 B0.5III 10 0
36 [MA93] 631 Em* 00 52 58.6429776984 -73 02 18.795049188   15.083 15.119   14.987 B0Ve 5 0
37 OGLE J005342.19-725309.4 HXB 00 53 42.1994697120 -72 53 09.700517796   14.695 14.737   14.46 B0Ve 9 0
38 SV* HV 1620 EB* 00 54 38.2336666176 -72 32 06.414177876 13.36 14.34 14.45 14.62 14.68 B0.5(IV)e? 35 0
39 [M2002] SMC 33823 * 00 55 30.4725348816 -72 27 15.751650672   14.45 14.62     B0III 6 0
40 [M2002] SMC 34005 * 00 55 33.9139896936 -72 02 43.841830344   14.80 15.01     O9V 6 0
41 AzV 170 s*b 00 55 42.4299731736 -73 17 30.523500780 12.86 13.82 14.11   14.25 O9.7I 30 0
42 [M2002] SMC 35491 * 00 55 59.5875596424 -72 19 54.252238152 13.72 14.78 14.83   14.96 O9IV 10 0
43 2MASS J00560168-7208251 * 00 56 01.6543820808 -72 08 24.712305036   14.88 15.15     O8V 6 0
44 SK 62 s*b 00 56 11.5319664528 -72 54 37.468399716 11.783 12.694 12.68 12.55 12.75 B2Ia 21 0
45 2MASS J00561228-7305511 * 00 56 12.2801558184 -73 05 51.124338888   13.21 13.38     O9.5III+B 6 0
46 [M2002] SMC 36325 * 00 56 14.25 -72 42 56.0   15.02 14.88     O9-9.5V 4 0
47 [SBV2013] B115 * 00 56 17.3240590800 -72 17 28.658898024 14.03 15.10 15.20   15.44 O9V 20 0
48 LIN 310 Em* 00 56 33.6841807848 -72 12 39.982407156   14.65 14.7     B0Ve 7 0
49 AzV 177 * 00 56 44.1036082560 -72 03 31.678578504 13.22 14.39 14.62   14.90 O4Vz 25 0
50 Cl* NGC 330 SW 95 Be* 00 56 44.3422559544 -72 29 06.512775972 13.49 14.68 14.76   14.92 O6.5-7.5IIIe 16 0
51 AzV 182 * 00 57 00.7180832856 -72 08 11.366066868 13.04 14.19 14.29   14.23 B0III 14 0
52 2MASS J00572792-7200263 * 00 57 27.9251872320 -72 00 26.181432108   14.22 14.33     O7V 6 0
53 2MASS J00580550-7226043 * 00 58 05.5674316176 -72 26 04.309278720   14.43 14.54     O9.5V 5 0
54 AzV 207 * 00 58 33.1896798552 -71 55 46.721984016 12.99 14.13 14.35   14.58 O7Vz((f)) 36 0
55 NGC 346 Cl* 00 59 04.4000 -72 10 39.000           ~ 490 0
56 2dFS 1382 * 00 59 20.2984678032 -72 14 25.017232776   14.74 14.85     O9.5V 9 0
57 AzV 226 * 00 59 20.7295412880 -72 17 10.615804836 12.97 14.12 14.19     O7IIIn((f)) 25 0
58 AzV 228 Em* 00 59 22.1643067200 -72 45 13.177810872   14.58 14.49     B0Ve 13 0
59 OGLE SMC-SC8 129167 Em* 00 59 27.4254247032 -72 48 37.219847616 13.54 14.58 14.81   15.09 O8.5V 10 0
60 2MASS J00593861-7144191 * 00 59 38.6048211792 -71 44 19.114537776   15.05 15.15     O8.5V 6 0
61 Cl* NGC 346 ELS 31 * 00 59 54.0614692656 -72 04 31.420184880 13.71 14.81 15.05   15.33 O8Vz 18 0
62 [MA93] 1186 Em* 01 00 07.3510813416 -72 34 26.669609112   14.56 14.6     B0Ve 6 0
63 AzV 244 * 01 00 10.7038536384 -71 48 06.051925296 13.27 14.27 14.47   14.73 O9-9.5V 11 0
64 AzV 249 s?b 01 00 20.3891710464 -72 41 22.676634816 12.88 13.59 13.71     B0I 13 0
65 OGLE SMC-SC9 41745 * 01 00 40.8272672112 -72 13 43.196181204 13.36 14.39 14.64   14.81 B1-3(II) 7 0
66 [MLD95] SMC 16 Be? 01 00 43.9414438872 -72 26 05.152501464 13.16 14.18 14.35   14.49 O9.5III 16 0
67 LIN 374 Em* 01 00 57.1148807760 -72 35 51.725394852   14.48 14.7     O8+B 8 0
68 SK 95 s*b 01 01 09.3913651632 -72 27 28.543237812 11.47 12.48 12.61   12.67 B1I 25 0
69 2MASS J01011473-7154306 * 01 01 14.7315019536 -71 54 30.692135988   15.04 15.19     O8V 6 0
70 AzV 267 * 01 01 15.6926628168 -72 06 35.367953616   14.58 14.84     O7.5-8V 18 0
71 LHA 115-S 32 Em* 01 01 29.5176849456 -72 23 20.039772048 12.58 13.85 13.85   13.69 O8IIIze 16 0
72 OGLE SMC-SC9 81569 * 01 01 31.1731667448 -72 20 08.072594232 13.92 15.06 15.22   15.55 O9V 9 0
73 2MASS J01013285-7216453 * 01 01 32.8435783416 -72 16 45.326174124   14.72 14.97     O5.5V 6 0
74 OGLE SMC-SC9 91851 * 01 01 54.9177961704 -72 07 27.455217852   14.80 14.98     O7II(f) 8 0
75 AzV 285 HXB 01 01 55.8081003144 -72 32 36.404929536 12.72 13.93 14.02   14.01 O6.5-7.5Ve 16 0
76 OGLE SMC-SC9 122249 * 01 02 10.9004898600 -72 25 05.621309868 13.69 14.76 14.90   15.07 O9.5III 7 0
77 [MA93] 1312 Em* 01 02 18.8605849320 -72 17 40.409856996 14.07 15.26 15.22   15.28 O6-9 10 0
78 SK 107 s*b 01 02 51.9499143600 -71 48 24.790164336 11.643 12.744 12.936   13.02 B0Iw 29 0
79 OGLE SMC-SC10 24428 * 01 03 29.7241000008 -72 17 55.611601944   14.87 14.95     O9III-V 11 0
80 AzV 350 * 01 04 19.8311642760 -72 40 49.374205176 12.93 13.89 14.02   14.19 B1III 9 0
81 [MA93] 1466 Em* 01 04 27.8449073448 -72 04 52.472684424   14.23 14.5     O5-7Ve 9 0
82 SXP 11.5 HXB 01 04 42.28 -72 54 03.7   14.81 14.81     O8.5-9.5IIIe 31 1
83 OGLE SMC-SC10 85867 * 01 04 53.2654678560 -72 40 34.153731156 13.80 14.90 15.11   15.41 O8-9V 9 0
84 NAME SMC Bar PoG 01 05 -72.6           ~ 235 0
85 SK 120 s?b 01 05 24.7610544984 -73 03 52.973560260 12.47 13.43 13.53   13.56 B1-1.5I 23 1
86 [M2002] SMC 62416 * 01 05 39.78 -72 20 27.0   14.59 14.68     O9.5V 6 0
87 LHA 115-S 47 Em* 01 06 06.3118248888 -72 18 03.485378304 15.88 13.90 14.03   13.98 B1-2(II) 20 0
88 AzV 398 s*b 01 06 09.8134902360 -71 56 00.746371284 13.15 13.94 13.98   13.71 O9.7Ia 44 0
89 OGLE SMC-SC11 17560 * 01 06 51.1603297032 -72 33 21.714033420 14.04 15.17 15.35   15.58 B0:(V) 8 0
90 2dFS 2252 * 01 07 06.9847177464 -72 08 46.739482908   14.99 15.19     O8V 9 0
91 OGLE SMC-ECL- 5221 EB* 01 07 07.2888505296 -73 11 10.036938768 14.04 14.75 14.97   15.24 O7V 10 0
92 SK 132 s*b 01 07 40.3905611664 -72 51 00.061708428 12.08 13.13 13.31 13.30 13.45 O9.5II(n) 42 0
93 AzV 429 EB* 01 07 59.8335369624 -72 00 53.979262812 13.40 14.49 14.69   14.91 O7Vz 19 0
94 2MASS J01080613-7233008 * 01 08 06.1325932800 -72 33 00.979412976   14.56 14.73     O7.5-8V 6 0
95 [MA93] 1656 Em* 01 08 18.0957430800 -72 36 25.011894528   15.123 15.109   14.834 O7.5-8.5Ve 6 0
96 LHA 115-S 54 Em* 01 08 25.8443187960 -72 23 27.317187312 12.72 13.99 13.89   13.82 B0(II)e 19 0
97 LHA 115-S 53 Em* 01 08 44.2485332472 -73 14 50.716667184 12.55 13.55 13.7   13.13 B0.2IIIe 22 0
98 AzV 439 * 01 08 51.0869885112 -71 49 51.681780912 13.47 14.49 14.68   14.87 O9.5III 15 0
99 AzV 440 * 01 08 56.0209984488 -71 52 46.695754200 13.42 14.30 14.58   14.76 O7.5III((f)) 22 0
100 [MA93] 1694 Em* 01 09 21.9491920248 -73 15 41.915109564 13.93 14.87 15.10   15.01 O6.5II(f) 11 0
101 AzV 446 * 01 09 25.4274489696 -73 09 29.906782668 13.37 14.38 14.61   14.91 O6.5Vz 21 0
102 AzV 447 * 01 09 28.3313994720 -72 17 14.784903672   13.79 14.01     B1II 12 0
103 AzV 448 * 01 09 48.2442870432 -72 30 19.328093424 13.37 14.48 14.69   14.96 O8.5Vn 14 0
104 AzV 451 * 01 10 26.0594119080 -72 23 29.007480732 12.65 13.68 13.98   14.24 O9.5V 20 0
105 AzV 461 * 01 11 25.5705843312 -72 09 48.802253292 13.22 14.40 14.61   14.94 O8V+neb 19 0
106 SK 145 s*b 01 11 25.9167352608 -72 31 21.276515892 11.463 12.464 12.596   11.60 B2.5Ia 38 0
107 SK 147 Em* 01 11 43.4911306608 -73 13 53.518808964 12.343 13.474 13.506   14.67 O7.5V 14 0
108 AzV 467 EB* 01 11 53.3734997520 -72 44 14.760756492 13.45 14.42 14.76   14.97 B0V 11 0
109 SK 148 * 01 12 29.0077488048 -72 29 29.054516928 11.913 13.014 13.176   13.32 O8.5II((f)) 41 0
110 [MA93] 1760 Em* 01 12 29.7296781864 -73 17 29.769753264   14.24 14.24 14.67 14.47 B0Ve 7 0
111 SK 151 s*b 01 13 00.3995614128 -73 17 04.124526036 12.66 13.62 13.63   13.41 O9.5I 22 0
112 SK 150 s*b 01 13 01.8742585512 -72 45 48.441989592 11.593 12.564 12.676   11.42 B2Ia 29 0
113 LHA 115-N 84C Em* 01 14 17.17 -73 15 49.4   14.65 14.4     O9V 32 0
114 GSC 09142-00856 * 01 14 22.5730175040 -73 13 23.253530988 13.68 14.61 14.74 14.89 14.82 O8.5V 8 0
115 LIN 508 Em* 01 14 55.0195828176 -72 21 38.101370184 13.26 14.41 14.3   14.25 O4-7Ve 19 0
116 2MASS J01151085-7256102 * 01 15 10.8416052696 -72 56 10.172118876   14.32 14.39     O8-9Ve 9 0
117 LHA 115-S 58 Em* 01 15 14.5813711800 -73 28 45.745201812 13.26 14.17 14.11   13.89 B0(III)e 12 0
118 AzV 484 * 01 15 39.2047472880 -73 23 49.463881584 12.84 13.78 13.89   14.16 O9.5III 14 0
119 2MASS J01165764-7319266 * 01 16 57.6105121872 -73 19 26.683001904 12.84 13.78 14.03   14.19 O6.5V 8 0
120 SK 160 HXB 01 17 05.1457288392 -73 26 36.014808156 12.23 13.00 13.15   13.17 O9.7Ia+ 858 0
121 SK 161 s*b 01 17 18.0465518064 -73 12 00.144497196   12.55 12.69     B0.5I 20 0
122 [MA93] 1860 Em* 01 18 53.9681685168 -73 09 38.338197264   14.27 14.4     O9.5III-V 10 0
123 2MASS J01193979-7314499 * 01 19 39.7984819944 -73 14 49.870769352   14.40 14.60     O9V 8 0
124 2MASS J01232110-7349518 * 01 23 21.1014160464 -73 49 51.728374380   14.24 14.46     O8V 8 0
125 2MASS J01232516-7322011 * 01 23 25.1569799688 -73 22 01.056606996   14.24 14.43     O9V: 9 0
126 2dFS 3712 * 01 24 51.2053382304 -73 27 01.820703564   14.15 14.36     O9III 9 0
127 2MASS J01253571-7311109 Pu* 01 25 35.7261677448 -73 11 10.883656248   13.82 14.03     O9.5V 6 0
128 2MASS J01263529-7315162 * 01 26 35.2855868400 -73 15 16.280587908   14.12 14.37     O9.5III 9 0
129 [M2002] SMC 82489 * 01 27 04.3091386320 -73 04 38.817504156   14.17 14.22     O6.5-7.5Ve 7 0
130 2MASS J01291256-7317267 * 01 29 12.5842476240 -73 17 26.657983500   14.28 14.39     B1-3(II)e 9 0
131 SK 187 * 01 30 50.2525498272 -73 22 58.905756120   12.99 13.18     O8.5III: 16 0
132 NAME Magellanic Clouds GrG 03 00 -71.0           ~ 7065 0
133 NAME LMC G 05 23 34.6 -69 45 22     0.4     ~ 17432 0
134 NAME 30 Dor Region reg 05 38.0 -69 06           ~ 236 0
135 NGC 4228 SBG 12 15 39.174 +36 19 36.80 10.63 10.30 9.93 9.74   ~ 965 1

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