2000AJ....120.1396H

Query : 2000AJ....120.1396H

2000AJ....120.1396H - Astron. J., 120, 1396-1409 (2000/September-0)

A near-infrared L-band survey of the young embedded cluster NGC 2024.

HAISCH K.E.Jr, LADA E.A. and LADA C.J.

Abstract (from CDS):

We present the results of the first sensitive L-band (3.4 µm) imaging study of the nearby young embedded cluster NGC 2024. Two separate surveys of the cluster were acquired in order to obtain a census of the circumstellar disk fraction in the cluster. We detected 257 sources to the mL≤12.0 completeness limit of our ∼110 arcmin2 primary survey region. An additional 26 sources with 12.0<L<14.0 were detected in the deeper survey of the central ∼6.25 arcmin2 region of the cluster. From an analysis of the JHKL colors of all sources in our largest area, we find an infrared excess fraction of ≥86%±8%. The JHKL colors suggest that the infrared excesses arise in circumstellar disks, indicating that the majority of the sources that formed in the NGC 2024 cluster are currently surrounded by, and likely formed with, circumstellar disks. The excess fractions remain very high, within the errors, even at the faintest L magnitudes from our deeper surveys, suggesting that disks form around the majority of the stars in very young clusters such as NGC 2024 independent of mass. From comparison with published JHKL observations of Taurus, we find the K-L excess fraction in NGC 2024 to be formally higher than in Taurus, although both fractions are quite high. Thus, existing L-band observations are consistent with a high initial incidence of circumstellar disks in both NGC 2024 and Taurus. Because NGC 2024 represents a region of much higher stellar density than Taurus, this suggests that disks may form around most of the YSOs in star-forming regions independent of environment. We find a relatively constant JHKL excess fraction with increasing cluster radius, indicating that the disk fraction is independent of location in the cluster. In contrast, the JHK excess fraction increases rapidly toward the central region of the cluster. The most likely cause for this increase is the contamination of the K-band measurements by bright nebulosity in the central regions of the cluster. This suggests that caution must be applied using only JHK-band observations to infer disk fractions in nebulous environments. Finally, we identify 45 candidate protostellar sources in the central regions of the cluster, and we find a lower limit on the protostellar phase of early stellar evolution in the NGC 2024 cluster of 0.4-1.4x105 yr, similar to that in Taurus.

Abstract Copyright: ∼

Journal keyword(s): Infrared: Stars - open clusters and associations: individual (NGC 2024) - Stars: Formation

Nomenclature: Table 2: Cl* NGC 2024 HLL NNN (Nos 1-142).

Simbad objects: 150

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Number of rows : 150
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 NAME Tau-Aur Complex SFR 04 30 +25.0           ~ 1453 0
2 NAME Orion Nebula Cluster OpC 05 35.0 -05 29           ~ 2514 0
3 NAME Horsehead Nebula DNe 05 40 59.0 -02 27 30           ~ 555 0
4 2MASS J05412424-0149348 Y*O 05 41 24.2500636656 -01 49 35.022968832   11.88 11.37     F5 15 0
5 2MASS J05412501-0152267 Y*O 05 41 25.0195706352 -01 52 26.815553148           ~ 5 0
6 Cl* NGC 2024 HLL 111 * 05 41 25.68 -01 55 50.4           ~ 1 0
7 2MASS J05412588-0157286 Y*O 05 41 25.8857623056 -01 57 28.796003604           ~ 12 0
8 2MASS J05412694-0154517 Y*O 05 41 26.9457618624 -01 54 51.894936720           M2.4 13 0
9 Cl* NGC 2024 HLL 72 Y*O 05 41 26.9580299088 -01 54 09.522395532           ~ 14 0
10 2MASS J05412711-0152098 Y*O 05 41 27.1175602008 -01 52 09.940285164           ~ 4 0
11 Cl* NGC 2024 HLL 9 * 05 41 28.29 -01 50 37.3           ~ 1 0
12 2MASS J05412880-0150024 Y*O 05 41 28.8098411688 -01 50 02.455415304           M1.7 13 0
13 2MASS J05412932-0151305 Y*O 05 41 29.3282899128 -01 51 30.612043800           M2.3 15 0
14 2MASS J05412953-0154255 Y*O 05 41 29.5352442432 -01 54 25.670675952           M1.3 18 0
15 2MASS J05413146-0155326 Y*O 05 41 31.4651003544 -01 55 32.902127688           ~ 10 0
16 2MASS J05413170-0153573 Y*O 05 41 31.7079176352 -01 53 57.470568612           ~ 6 0
17 2MASS J05413186-0152200 Y*O 05 41 31.8618799104 -01 52 20.182551204           ~ 8 0
18 2MASS J05413186-0154537 Y*O 05 41 31.8668188776 -01 54 53.874959688           ~ 4 0
19 2MASS J05413194-0155186 Y*O 05 41 31.9451836176 -01 55 18.821485020           M2.1 17 0
20 2MASS J05413283-0152126 Y*O 05 41 32.8390614672 -01 52 12.781008156           ~ 5 0
21 2MASS J05413337-0151271 Y*O 05 41 33.3818579112 -01 51 27.225823392           M1.75 10 0
22 2MASS J05413347-0155134 Y*O 05 41 33.4772996640 -01 55 13.580115816           ~ 3 0
23 2MASS J05413371-0156068 Y*O 05 41 33.72 -01 56 06.9           ~ 4 0
24 2MASS J05413382-0153234 Y*O 05 41 33.8285848968 -01 53 23.586220284           ~ 14 0
25 2MASS J05413386-0153087 Y*O 05 41 33.8642235384 -01 53 08.851287048           M6.75 6 0
26 2MASS J05413397-0153510 Y*O 05 41 33.9804092424 -01 53 51.137463660           M2.2 11 0
27 2MASS J05413441-0153194 Y*O 05 41 34.4118839472 -01 53 19.616764632           ~ 12 0
28 2MASS J05413448-0154410 Y*O 05 41 34.4892063600 -01 54 41.216502024           M1.75 8 0
29 [BCB89] IRS 19 Y*O 05 41 34.8714955080 -01 55 18.642195408           ~ 11 0
30 2MASS J05413537-0152116 Y*O 05 41 35.37 -01 52 11.6           ~ 4 0
31 2MASS J05413545-0152288 Y*O 05 41 35.4591344352 -01 52 28.944890904           M1.5 13 0
32 Cl* NGC 2024 HLL 118 Y*O 05 41 35.81 -01 56 22.3           ~ 6 0
33 2MASS J05413585-0157122 Y*O 05 41 35.86 -01 57 12.2           ~ 3 0
34 [BCB89] IRS 18 Y*O 05 41 36.2397031704 -01 54 24.347553120           ~ 13 0
35 2MASS J05413632-0153393 Y*O 05 41 36.3258220464 -01 53 39.464689704           ~ 2 0
36 2MASS J05413638-0155548 Y*O 05 41 36.3893082840 -01 55 55.056985752           ~ 3 0
37 Cl* NGC 2024 HLL 63 * 05 41 36.53 -01 53 56.9           ~ 1 0
38 2MASS J05413654-0153188 Y*O 05 41 36.5430918048 -01 53 19.027496976           ~ 6 0
39 Cl* NGC 2024 HLL 33 * 05 41 36.62 -01 52 45.4           ~ 1 0
40 Cl* NGC 2024 HLL 71 * 05 41 36.63 -01 54 10.7           ~ 1 0
41 Cl* NGC 2024 HLL 67 * 05 41 36.75 -01 54 01.2           ~ 1 0
42 Cl* NGC 2024 HLL 32 * 05 41 36.83 -01 52 35.6           ~ 1 0
43 2MASS J05413682-0154479 Y*O 05 41 36.8358422448 -01 54 48.118045788           M7.25 6 0
44 2MASS J05413693-0153393 Y*O 05 41 36.9437944344 -01 53 39.473630844           ~ 5 0
45 2MASS J05413730-0151404 Y*O 05 41 37.304 -01 51 40.40           M1.75 3 0
46 [BCB89] IRS 12 Y*O 05 41 37.3414165248 -01 53 13.454106216           ~ 15 0
47 Cl* NGC 2024 HLL 34 Y*O 05 41 37.4001901512 -01 52 44.837581944           ~ 5 0
48 2MASS J05413744-0149532 Y*O 05 41 37.4490454344 -01 49 53.354531568           ~ 15 0
49 Cl* NGC 2024 HLL 80 * 05 41 37.58 -01 54 27.0           ~ 1 0
50 [BCB89] IRS 15 Y*O 05 41 37.7431192008 -01 53 51.578246832           ~ 13 0
51 Cl* NGC 2024 HLL 86 * 05 41 37.82 -01 54 38.6           ~ 1 0
52 NGC 2024 1 Y*O 05 41 37.8554929272 -01 54 36.640829556   13.58 12.17     B0.5V 60 0
53 2MASS J05413789-0153112 Y*O 05 41 37.9057871976 -01 53 11.393006748           M 15 0
54 2MASS J05413807-0153572 Y*O 05 41 38.0835551256 -01 53 57.311572272           ~ 4 0
55 Cl* NGC 2024 HLL 137 Y*O 05 41 38.1748077696 -01 58 17.822746848           ~ 4 0
56 2MASS J05413818-0154549 Y*O 05 41 38.19 -01 54 54.9           ~ 5 0
57 2MASS J05413821-0155361 Y*O 05 41 38.2182613896 -01 55 36.400660032           M2.3 17 0
58 [BCB89] IRS 11 Y*O 05 41 38.2491466584 -01 53 09.237286968           ~ 12 0
59 2MASS J05413843-0150383 Y*O 05 41 38.43240 -01 50 38.3640           ~ 15 0
60 [BCB89] IRS 10 Y*O 05 41 38.5918815672 -01 53 22.920556200           ~ 8 0
61 2MASS J05413861-0157301 Y*O 05 41 38.6154290400 -01 57 30.281150268           ~ 3 0
62 2MASS J05413871-0154289 Y*O 05 41 38.71 -01 54 29.0           ~ 3 0
63 Cl* NGC 2024 HLL 114 Y*O 05 41 38.7691943544 -01 56 02.591183976           ~ 15 0
64 2MASS J05413901-0151453 Y*O 05 41 39.02 -01 51 45.4           M4.75 5 0
65 Cl* NGC 2024 HLL 122 Y*O 05 41 39.062 -01 56 26.44           ~ 5 0
66 [BCB89] IRS 14 Y*O 05 41 39.0936364368 -01 53 58.471752444           ~ 17 0
67 2MASS J05413913-0152073 Y*O 05 41 39.1308722424 -01 52 07.467275244           ~ 19 0
68 [BCB89] IRS 13 Y*O 05 41 39.19320 -01 54 14.0724           ~ 19 0
69 2MASS J05413948-0153336 Y*O 05 41 39.489 -01 53 33.68           ~ 3 0
70 [BCB89] IRS 9 Y*O 05 41 39.49 -01 53 26.9           ~ 10 1
71 [BCB89] IRS 8 Y*O 05 41 40.16 -01 53 34.4           ~ 16 0
72 2MASS J05414026-0152205 Y*O 05 41 40.27 -01 52 20.6           ~ 4 0
73 2MASS J05414026-0150522 Y*O 05 41 40.2710198664 -01 50 52.382093892           M1.75 16 0
74 2MASS J05414059-0155185 Y*O 05 41 40.597 -01 55 18.56           ~ 2 0
75 2MASS J05414134-0153326 Y*O 05 41 41.3524630 -01 53 32.838938           ~ 12 0
76 2MASS J05414138-0153522 Y*O 05 41 41.38 -01 53 52.3           ~ 4 0
77 2MASS J05414148-0154390 Y*O 05 41 41.49 -01 54 39.1           ~ 7 0
78 [BCB89] IRS 30 Y*O 05 41 41.6490369408 -01 57 54.774093168           ~ 17 0
79 2MASS J05414167-0154128 Y*O 05 41 41.67 -01 54 12.8           ~ 4 0
80 2MASS J05414177-0151456 Y*O 05 41 41.7762984120 -01 51 45.803561760           ~ 5 0
81 Cl* NGC 2024 HLL 78 Y*O 05 41 41.982 -01 54 24.00           ~ 8 0
82 2MASS J05414220-0155099 Y*O 05 41 42.2045227824 -01 55 10.083703728           M2.3 12 0
83 Cl* NGC 2024 HLL 70 * 05 41 42.45 -01 54 11.3           ~ 1 0
84 Cl* NGC 2024 HLL 97 Y*O 05 41 42.46 -01 55 02.6           ~ 5 0
85 2MASS J05414254-0154028 Y*O 05 41 42.540 -01 54 02.89           ~ 3 0
86 2MASS J05414254-0156175 Y*O 05 41 42.5450936976 -01 56 17.751591600           ~ 4 0
87 Cl* NGC 2024 BSC 76 Y*O 05 41 42.62 -01 54 45.7           ~ 6 0
88 NAME Flame Nebula HII 05 41 42.7 -01 54 44           ~ 715 1
89 2MASS J05414280-0154360 Y*O 05 41 42.80 -01 54 36.1           ~ 6 0
90 NAME Ori B MoC 05 41 43.0 -01 54 44           ~ 1498 0
91 NGC 2024 Cl* 05 41 43 -01 50.5           ~ 1198 1
92 2MASS J05414334-0153298 Y*O 05 41 43.34 -01 53 29.9           ~ 3 0
93 [BCB89] IRS 24 Y*O 05 41 43.45 -01 56 42.5           ~ 5 0
94 2MASS J05414349-0153247 Y*O 05 41 43.493 -01 53 24.72           ~ 3 0
95 2MASS J05414368-0151353 Y*O 05 41 43.686 -01 51 35.31           ~ 3 0
96 2MASS J05414398-0158454 Y*O 05 41 43.9898720088 -01 58 45.605862012           ~ 15 0
97 Cl* NGC 2024 HLL 105 * 05 41 44.17 -01 55 20.4           ~ 2 0
98 2MASS J05414436-0154203 Y*O 05 41 44.37 -01 54 20.3           ~ 4 0
99 [BCB89] IRS 3 Y*O 05 41 44.4045095712 -01 55 23.095022772           M1.9 27 0
100 [BCB89] IRS 29 Y*O 05 41 44.5140764640 -01 57 40.415398416           M1.6 13 0
101 2MASS J05414482-0154251 Y*O 05 41 44.82 -01 54 25.1           ~ 9 0
102 2MASS J05414483-0154357 Y*O 05 41 44.834 -01 54 35.72           ~ 9 0
103 Cl* NGC 2024 HLL 19 Y*O 05 41 45.08640 -01 51 44.3088           ~ 14 0
104 [BCB89] IRS 20 Y*O 05 41 45.127 -01 54 47.09           ~ 16 0
105 [BCB89] IRS 22 Y*O 05 41 45.4911975768 -01 56 17.217922956           M3.3 14 0
106 2MASS J05414563-0151228 Y*O 05 41 45.6402964344 -01 51 22.979017476           ~ 5 0
107 Cl* NGC 2024 HLL 96 Y*O 05 41 45.696 -01 55 04.75           ~ 6 0
108 Cl* NGC 2024 HLL 91 * 05 41 45.74 -01 54 50.7           ~ 1 0
109 [BCB89] IRS 2 Y*O 05 41 45.81 -01 54 29.8           B 105 0
110 Cl* NGC 2024 HLL 57 * 05 41 45.82 -01 53 46.2           ~ 1 0
111 Cl* NGC 2024 HLL 58 Y*O 05 41 46.21368 -01 53 46.6980           ~ 12 0
112 2MASS J05414641-0150111 Y*O 05 41 46.4188015632 -01 50 11.340661632           M2.2 23 0
113 EM* LkHA 289 Y*O 05 41 46.9098903048 -01 49 57.488992716   20       ~ 21 0
114 2MASS J05414702-0149265 Y*O 05 41 47.0300299032 -01 49 26.698699164           M1.5 15 0
115 2MASS J05414712-0150353 Y*O 05 41 47.1286987080 -01 50 35.492991180           ~ 16 0
116 2MASS J05414723-0158202 Y*O 05 41 47.23 -01 58 20.3           ~ 5 0
117 Cl* NGC 2024 HLL 142 * 05 41 47.29 -01 59 28.8           ~ 1 0
118 2MASS J05414780-0159036 Y*O 05 41 47.8136885184 -01 59 03.573802572           M2.6 17 0
119 2MASS J05414861-0153495 Y*O 05 41 48.61 -01 53 49.6           ~ 3 0
120 2MASS J05414868-0154159 Y*O 05 41 48.68 -01 54 15.9           ~ 4 0
121 2MASS J05414908-0154087 Y*O 05 41 49.0916334792 -01 54 08.745223428           ~ 3 0
122 2MASS J05414934-0153318 Y*O 05 41 49.35 -01 53 31.9           ~ 4 0
123 2MASS J05414966-0153271 Y*O 05 41 49.6753190928 -01 53 27.130103916           M2.75 5 0
124 2MASS J05414980-0156272 Y*O 05 41 49.8155194296 -01 56 27.288895596           ~ 2 0
125 2MASS J05414983-0152560 Y*O 05 41 49.83 -01 52 56.1           ~ 5 0
126 2MASS J05415003-0157306 Y*O 05 41 50.0435758560 -01 57 30.683954556           M2.0 12 0
127 [BCB89] IRS 28 Y*O 05 41 50.1540611808 -01 57 44.952809940           ~ 20 0
128 [BCB89] IRS 6 Y*O 05 41 50.5093178232 -01 53 15.514595772           ~ 14 0
129 2MASS J05415087-0153128 Y*O 05 41 50.87 -01 53 12.8           ~ 5 0
130 2MASS J05415170-0152081 Y*O 05 41 51.70 -01 52 08.2           ~ 4 0
131 [BCB89] IRS 26 Y*O 05 41 52.1649829968 -01 57 17.482242924           M1.9 20 0
132 [BCB89] IRS 25 Y*O 05 41 52.92 -01 56 29.7           ~ 8 0
133 Cl* NGC 2024 HLL 123 Y*O 05 41 52.9514358912 -01 56 35.174645556           ~ 10 0
134 [BCB89] IRS 27 Y*O 05 41 53.2008056520 -01 57 44.124446772           ~ 18 0
135 [BCB89] IRS 21 Y*O 05 41 53.88 -01 55 16.4           ~ 16 0
136 2MASS J05415430-0155566 Y*O 05 41 54.3100459272 -01 55 56.729916660           ~ 3 0
137 2MASS J05415472-0157273 Y*O 05 41 54.7306333944 -01 57 27.339604200           ~ 3 0
138 2MASS J05415492-0156483 Y*O 05 41 54.9319087104 -01 56 48.402036960           ~ 5 0
139 Cl* NGC 2024 HLL 27 * 05 41 55.6936558104 -01 52 18.612966648           ~ 10 0
140 2MASS J05415579-0155092 Y*O 05 41 55.7937556560 -01 55 09.317484012           ~ 6 0
141 2MASS J05415613-0150491 Y*O 05 41 56.1372103704 -01 50 49.325996112           ~ 3 0
142 2MASS J05415668-0155526 Y*O 05 41 56.6883872928 -01 55 52.647389976           M5.25 4 0
143 2MASS J05415697-0150331 Y*O 05 41 56.9752983216 -01 50 33.299169612           ~ 4 0
144 2MASS J05415786-0151278 Y*O 05 41 57.8655477888 -01 51 27.984742056           ~ 9 0
145 2MASS J05415930-0159108 Y*O 05 41 59.3125840056 -01 59 10.857857784           M2.8 18 0
146 2MASS J05420172-0156299 Y*O 05 42 01.7290975680 -01 56 29.946562800           M2.3 13 0
147 2MASS J05420467-0157389 Y*O 05 42 04.6813916328 -01 57 38.976563700           ~ 18 0
148 2MASS J05420597-0152522 Y*O 05 42 05.9712811080 -01 52 52.388308632           M1.3 14 0
149 LDN 1630 DNe 05 45.5 -00 59           ~ 392 0
150 NAME Ophiuchus Molecular Cloud SFR 16 28 06 -24 32.5           ~ 3969 1

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