我們利用多波段觀測來研究兩個在巴納德星雲的毫米/次毫米天體，他們的名稱是Barnard 1-bN和Barnard 1-bS。從這兩個天體所發出的塵埃連續輻射訊號，我們發現他們物質分布很緻密，且物質本身相當低溫（塵埃溫度10-16 K）。Spitzer的MIPS望遠鏡所拍出的24和60微米波段影像裡，這兩個天體並沒有被偵測到，這表示他們還包裹在雲深處。由SMA觀測的CO（J=2-1）譜線資料顯現出Barnard 1-bS有噴流，Barnard 1-bN則是疑似有噴流。這些噴流都不是很大（大約2000 AU大小）。這個結果指出這兩個天體已經蘊含著Class 0原恆星。另一方面，這兩個天體的化學特性反而相似於前恆星核：N2D+（J=3-2）譜線訊號很強而且和塵埃連續輻射訊號的分布很一致。反之，H13CO+（J=1-0）譜線訊號則很微弱，甚至是沒有偵測到。這樣的化學特性可能是因為在低溫高密度環境中，H13CO+ 分子已經分解附著在塵粒上所導致。而這樣子的化學特性是相似於前恆星核的化學特性。因此，綜合我們所發現的這兩個天體的物理及化學特性，我們可以知道Barnard 1-bN和Barnard 1-bS是在恆星形成非常早期的天體，他們的演化時期可能正好落在前恆星核時期與Class 0原恆星時期中間。

The physical and chemical properties of two mm/sub-mm sources in Barnard cloud, Barnard 1-bN and Barnard 1-bS, are studied with multi-wavelength observations. The dust continuum from these two sources shows spatially compact distribution and very cold spectral energy distributions (T$_{dust}$=10--16 K). These two sources have no mid-IR counterpart in the Spitzer MIPS 24 and 60 micron bands, indicating that they are deeply embedded. The CO J=2--1 data obtained with the SMA suggest that B1-bS and probably B1-bN are associated with the compact ($sim$ 2000; AU size) molecular outflows. These results suggest that Barnard 1-bN and Barnard 1-bS are already harboring Class 0 protostars. On the other hand, the chemical properties of these two sources are similar to those of pre-stellar cores: the N$_2$D$^+$ J=3--2 emission is strong (0.3 K for B1-bN and 0.1 K for B1-bS) and clearly traces the two compact sources, while the H$^{13}$CO$^+$ J=1--0 emission is weak or barely detected near or at the continuum peaks. This lack of H$^{13}$CO$^+$ emission is probably due to the depletion of the H$^{13}$CO$^+$ molecule onto the grain under the condition of low temperature and high density, as in the case of pre-stellar cores. The observed physical and chemical properties suggest that B1-bN and B1-bS are in the very beginning stage of protostellar evolution, probably in the evolutionary stage between pre-stellar core and class 0 source.

[1] Aalto, S., Booth, R. S., Black, J. H. & Johansson, L. E. B. 1995, A&A,
300, 369
[2] Andr’e, P., Ward-Thompson, D., & Barsony, M. 1993, ApJ, 406, 122
[3] Andr’e, P. & Monterle, T. 1994, ApJ, 420, 837
[4] Andr’e, P., Ward-Thompson, D., & Barsony, M. 2000, Protostars and
Planets IV, 59
[5] Bachiller, R., Menten, K. M., & Del Rio-Alvarez, S. 1990, A&A, 236,
461
[6] Bate, M. 1998, ApJ, 508, L95
[7] Beichman C. A., Myers P. C., Emerson J. P., Harris S., Mathieu R.,
Benson P. J., & Jennings R. E., 1986, ApJ, 307, 337
[8] Alves, J. Lada, C. J., & Lada, E. A. 1999, ApJ, 515, 265
[9] Benson, P. J., & Myers, P. C. 1989, ApJS, 71, 89
[10] Bergin, E. A., & Langer, W. D. 1997, ApJ, 486, 316
[11] Bergin, E. A., Alves, J., Huard, T., et al. 2002, ApJ, 570, 101
57
[12] Bergin, E. A. & Tafalla, M. 2007, ARA&A, 45, 339
[13] Borgman, J., & Blaauw, A. 1964, Bull. Astron. Inst. Netherlands, 17,
358
[14] Cabrit, S., & Bertout, C. 1990, ApJ, 348, 530
[15] Crapsi, A., Caselli, P., Walmsley, C. M., et al. 2005, ApJ, 619, 379
[16] Caselli, P., Walmsley, C. M., Tafalla, M., Dore, L., & Myers, P. C. 1999,
ApJ, 523, L165
[17] Chen, H., Myers, P. C., Ladd, E. F., & Wood, D. O. S. 1995, ApJ, 445,
377
[18] Chen, H., Grenfell, T. G., Myers, P. C., & Hughes, J. D. 1997, ApJ,
478, 295
[19] ˘
Cernis, K. 1990, Ap&SS, 166, 315
[20] ˘
Cernis, K. & Straizys, V. 2003, BaltA, 12, 301
[21] D., Zeeuw, P. T., Hoogerwerf, R., de Bruijne, J. H. J., Brown, A. G. A.,
& Blaauw, A. 1999, AJ, 117, 354
[22] Emprechtinger M., Caselli P, Volgenau N. H, Stutzki J, & Wiedner M.
C 2009, A&A, 493, 89
[23] Enoch, M. L., Young, K. E., Glenn, J., et al. 2006, ApJ, 638, 293
[24] Frerking, M. A., Langer, W. D., & Wilson, R. W. 1987, ApJ, 313, 320
[25] Froebrich, D. 2005, ApJS, 156, 169
58
[26] Gerin, M., Pearson, J. C., Roue?, E., Falgarone, E., & Phillips, T. G.
2001, ApJ, 551, L193
[27] Hatchell, J., Richer, J. S., Fuller, G. A., Qualtrough, C. J., Ladd, E. F.,
& Chandler, C. J. 2005, A&A, 440, 151
[28] Hatchell J., Fuller G.A., Richer J.S., 2007, A&A, 472, 187
[29] Hirano, N., Kameya, O., Mikami, H., Saito, S., Umemoto, T., & Ya-
mamoto, S. 1997, ApJ, 478, 631
[30] Hirano, N., Kamazaki, T., Mikami, H., Ohashi, N., & Umemoto, T.
1999, in Proc. Star Formation 1999, Nagoya, Japan, ed. T. Nakamoto
(Nagoya: Nobeyama Radio Obs.), 181
[31] Hirota, T., et al. 2008, PASJ, 60, 37
[32] Jorgensen, J. K., Schier, F. L., & van Dishoeck, E. F. 2004, A&A, 416,
603
[33] Jorgensen, J. K., Harvey, P. M., Evans, II, N. J., et al. 2006, ApJ, 645,
1246
[34] Kuiper, T. B. H., Langer, W. D., & Velusamy, T. 1996, ApJ, 468, 761
[35] Kramer, C., Alves, J., Lada, C. J., et al. 1999, A&A, 342, 257
[36] Lada, C. J. 1987, in Star Formation Region, ed. M. Peimbert, J. Jugaku,
& P. W. J. L. Brand (Dordrecht: Reidel), IAU Symp., 115, 1
[37] Langer, W. & Penzias, A., 1990, ApJ, 357, 477
[38] Larson, R. B. 1969, MNRAS, 145, 271
59
[39] Lee, C.-F., Ho, P. T. P, Palau, A., Hirano, N., Bourke, T. L, Shang,
H.,& Zhang, Q. 2007, ApJ, 670, 1188
[40] Lis, D. C., Gerin, M., Phillips, T. G., & Motte, F. 2002, ApJ, 569, 322
[41] Marcelino, N., Cernicharo, J., Roueff, E., Gerin, M., & Mauersberger,
R., 2005, ApJ, 620, 308
[42] Matthews, B. C., & Wilson, C. D. 2002, ApJ, 574, 822
[43] Matthews, B. C., Hogerheijde, M. R., Jrgensen, J. K. & Bergin, E. A.
2006, ApJ, 652, 1374
[44] Mizuno, A., Onishi, T., Hayashi, M., Ohashi, N., Sunada, K., Hasegawa,
T., & Fukui, Y. 1994, Nature, 368, 719241
[45] Myers, P. C., & Benson, P. J. 1983, ApJ, 266, 309
[46] Myers, P. C., Fuller, G. A., Mathieu, R. D., et al. 1987, ApJ, 319, 340
[47] Myers, P. C., & Ladd, E. F. 1993, ApJ, 413, L47
[48] Myers, P. C., Adams, F. C., Chen, H., & Schaff, E. 1998, ApJ, 492, 703
[49] Ossenkopf, V., & Henning, Th. 1994, A&A, 291, 943
[50] Saito, M., Sunada, K., Kawabe, R., Kitamura, Y., & Hirano, N. 1999,
ApJ, 518, 334
[51] Saito, M., Kawabe, R., Kitamura, Y., & Sunada, K. 2001, ApJ, 547, 840
[52] Saraceno, P., Andr’e, P., Ceccarelli, C., et al. 1996, A&A, 309, 827
[53] Redman, M. P., Rawlings, J. M. C., Nutter, D. J., Ward-Thompson, D.,
& Williams, D. A. 2002, MNRAS, 337, L17
60
[54] Shu, F. H., Adams, F. C., & Lizano, S. 1987, ARA&A, 25, 23
[55] Tafalla, M., Myers, P. C., Caselli, P., et al. 2002, ApJ, 569, 815
[56] Tafalla, M., Myers, P. C., Caselli, P., & Walmsley, C. M. 2004, A&A,
416, 191
[57] Takakuwa, S., Ohashi, N., & Hirano, N 2003, ApJ, 590, 932
[58] Walawender, J., Bally, J., Kirk, H., & Johnstone, D. 2005, AJ, 130, 1795
[59] Walawender, J., Reipurth, B., & Bally, J. 2009, AJ, 137,3254
[60] Ward-Thompson, D., Scott, P. F., Hills, R. E., & Andre P. 1994, MN-
RAS, 268, 276
[61] Wilking, B. A., Lada, C. J., & Young, E. T. 1989, ApJ, 340, 823
[62] Willacy, K., Langer, W. D., & Velusamy, T. 1998, ApJ, 507, L171
[63] Vogel, S. N., Wright, M. C. H., Plambeck, R. L., & Welch, W. J. 1984,
ApJ, 283, 655
[64] Yu, T., & Chernin, L. M. 1997, ApJ, 479, L63