2008A&A...486..245C


Query : 2008A&A...486..245C

2008A&A...486..245C - Astronomy and Astrophysics, volume 486, 245-254 (2008/7-4)

Characterizing the nature of embedded young stellar objects through silicate, ice and millimeter observations.

CRAPSI A., VAN DISHOECK E.F., HOGERHEIJDE M.R., PONTOPPIDAN K.M. and DULLEMOND C.P.

Abstract (from CDS):

Determining the evolutionary stage of a Young Stellar Object (YSO) is of fundamental importance to test star formation theories. Classification schemes for YSOs are based on evaluating the degree of dissipation of the surrounding envelope, whose main effects are the extinction of the optical radiation from the central YSO and re-emission in the far-infrared to millimeter part of the electromagnetic spectrum. Since extinction is a property of column density along the line of sight, the presence of a protoplanetary disk may lead to a misclassification of pre-main sequence stars with disks when viewed edge-on. We performed radiative transfer calculations to show the effects of different geometries on the main indicators of YSO evolutionary stage. In particular we tested not only the effects on the infrared colors, like the slope α of the flux between 2.2 and 24µm, but also on other popular indicators of YSO evolutionary stage, such as the bolometric temperature and the optical depth of silicates and ices. We used the axisymmetric 3D radiative transfer codes RADMC and RADICAL to calculate the spectral energy distribution including silicates and ice features in a grid of models covering the range of physical properties typical of embedded and pre-main sequence sources. Our set of models compares well with existing observations, supporting the assumed density parametrization and the adopted dust opacities. We show that for systems viewed at intermediate angles (25°-70°) the ``classical'' indicators of evolution are able to classify the degree of evolution of young stellar objects since they accurately trace the envelope column density, and they all agree with each other. On the other hand, edge-on system are misclassified for inclinations larger than ∼65°±5°, where the spread is mostly due to the range of mass and the flaring degree of the disk. In particular, silicate emission, typical of pre-main sequence stars with disks, turns into silicate absorption when the disk column density along the line of sight reaches 1x1022cm–2, corresponding e.g. to a 5x10–3M flaring disk viewed at 64°. A similar effect is noticed in all the other classification indicators studied: α, Tbol, and the H2O and CO2 ice absorption strengths. This misclassification has a large impact on the nature of the flat-spectrum sources (α≃0), whose number can be explained by simple geometrical arguments without invoking evolution. A reliable classification scheme using a minimal number of observations is constituted by observations of the millimeter flux with both a single dish and an interferometer.

Abstract Copyright:

Journal keyword(s): stars: formation - stars: pre-main sequence - ISM: dust, extinction

CDS comments: In table 2 , 17 objects not identified.

Simbad objects: 48

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Number of rows : 48
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 CoKu NGC 1333 Star 1 Y*O 03 25 09.43032 +30 46 21.5796           M2.6 98 0
2 IRAS 03235+3004 Y*O 03 26 37.425 +30 15 28.39           ~ 87 0
3 NAME LDN 1455 IRS 1 cor 03 27 39.08 +30 13 03.1           ~ 161 0
4 NAME LDN 1455 IRS 4 cor 03 27 43.23 +30 12 28.9           ~ 74 0
5 2MASS J03274767+3012043 Y*O 03 27 47.6828532408 +30 12 04.456916028     19.6     M3.0 103 1
6 2MASS J03280041+3008012 Y*O 03 28 00.411 +30 08 01.28           ~ 53 0
7 2MASS J03283450+3100510 Y*O 03 28 34.501 +31 00 51.01           ~ 76 0
8 IRAS 03271+3013 cor 03 30 15.159 +30 23 49.38           ~ 70 0
9 IRAS 03301+3111 Y*O 03 33 12.8440487256 +31 21 24.139522188           M1.8 65 0
10 NAME Perseus Cloud SFR 03 35.0 +31 13           ~ 1371 0
11 IRAS 03439+3233 Y*O 03 47 05.44704 +32 43 08.4324           ~ 57 0
12 IRAS 03445+3242 Y*O 03 47 41.603 +32 51 43.79           ~ 201 0
13 IRAS 04016+2610 Y*O 04 04 43.07064 +26 18 56.3904           ~ 259 0
14 NAME IRAS 04108+2803B Y*O 04 13 54.71688 +28 11 32.8992           K0-M3 40 0
15 IRAS 04169+2702 Y*O 04 19 58.44936 +27 09 57.0672           K0-M4 117 1
16 IRAS 04181+2654 Y*O 04 21 11.46888 +27 01 09.4044           G0-M3 63 0
17 IRAS 04239+2436 Y*O 04 26 56.29704 +24 43 35.3280           ~ 156 0
18 [EM98] DG Tau B cRN Y*O 04 27 02.66088 +26 05 30.4548           ~ 179 0
19 V* GV Tau TT* 04 29 23.7314759229 +24 33 00.216016292 19.20         K7 283 0
20 RAFGL 5123 Y*O 04 31 34.07736 +18 08 04.9020           K3V/M3III 864 0
21 IRAS 04302+2247 Y*O 04 33 16.50096 +22 53 20.4000           ~ 176 0
22 IRAS 04325+2402 Y*O 04 35 35.39160 +24 08 19.4244           ~ 159 0
23 EM* LkCa 15 Or* 04 39 17.7911622816 +22 21 03.390090984   13.01 12.03 11.61   K5:Ve 691 1
24 NAME Taurus Complex SFR 04 41.0 +25 52           ~ 4429 0
25 IRAS 04381+2540 Y*O 04 41 12.67920 +25 46 35.4216           K0-M2 129 1
26 2MASS J08254384-5100326 Y*O 08 25 43.85 -51 00 32.7           ~ 317 1
27 TWA 3 ** 11 10 27.894072 -37 31 51.96612   13.53 12.05 11.61 9.29 M4Ve+M4Ve 211 0
28 TWA 3A TT* 11 10 27.9121410480 -37 31 51.535547940   14.04 12.57   9.10 M4Ve 210 0
29 2MASS J12590656-7707401 Y*O 12 59 06.56 -77 07 40.1           K4.5 48 0
30 CG 12 CGb 13 57 42.2 -39 56 21           ~ 49 1
31 CD-40 8434 TT* 14 08 10.1545500744 -41 23 52.573291080   13.42 12.18 11.71 10.506 K7IVe 361 0
32 Barnard 228 cor 15 43 00.9 -34 08 48           ~ 68 0
33 IRAS 15398-3359 Y*? 15 43 02.21016 -34 09 07.7112       18.38 21.72 ~ 175 0
34 VSSG 30 Y*O 16 26 44.19504 -24 34 48.3492           ~ 135 0
35 WL 6 Y*O 16 27 21.80448 -24 29 53.3616           ~ 115 0
36 CRBR 2422.8-3423 Y*O 16 27 24.61320 -24 41 03.4080           ~ 92 1
37 NAME Ophiuchus Molecular Cloud SFR 16 28 06 -24 32.5           ~ 3636 1
38 HBC 650 TT* 16 34 29.32 -15 47 01.4           K3.0 177 2
39 EM* LkHA 346 Y*O 17 11 17.2853820264 -27 25 08.241647988   15       ~ 37 1
40 HD 163296 Ae* 17 56 21.2881851168 -21 57 21.871819008 7.00 6.93 6.85 6.86 6.67 A3VaekA1mA1 1113 0
41 NAME Serpens Cloud SFR 18 29 49 +01 14.8           ~ 1103 2
42 [EC89] SVS 4-5 Y*O 18 29 57.59 +01 13 00.6           ~ 35 1
43 2MASS J18295820+0115216 Y*O 18 29 58.2037073472 +01 15 21.610474308           K7.0 40 0
44 HD 179218 Ae* 19 11 11.2538919456 +15 47 15.636008472 7.55 7.476 7.39 7.25 7.21 A0Ve 255 0
45 V* WW Vul Ae* 19 25 58.7494120560 +21 12 31.333658616 11.46 10.99 10.25 10.38 10.12 A2IVe 224 0
46 HD 184761 PM* 19 34 58.9695325200 +27 13 31.226414628   7.00 6.73     A3 28 0
47 NAME LDN 1014 IRS Y*O 21 24 07.58 +49 59 08.9           ~ 81 0
48 PSCz Q23238+7401 Y*O 23 25 46.65 +74 17 37.2           ~ 58 1

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