TWO EXTREME YOUNG OBJECTS IN BARNARD 1-b

• Published in: The Astrophysical journal Vol. 789; no. 1; p. 50
• Main Authors: Hirano, Naomi, Liu, Fang-chun
• Format: Journal Article
• Language: English
• Published: United States 01.07.2014
• Subjects: ABUNDANCE; ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; BOLOMETERS; CARBON MONOXIDE; DUSTS; EMISSION; ENERGY SPECTRA; LUMINOSITY; MAGNETOHYDRODYNAMICS; PROTOSTARS; SIMULATION; STARS; VELOCITY
• ISSN: 0004-637X; 1538-4357
• DOI: 10.1088/0004-637X/789/1/50

Two submillimeter/millimeter sources in the Barnard 1b (B1-b) core, B1-bN and B1-bS, have been studied in dust continuum, H{sup 13}CO{sup +} J = 1-0, CO J = 2-1, {sup 13}CO J = 2-1, and C{sup 18}O J = 2-1. The spectral energy distributions of these sources from the mid-IR to 7 mm are characterized by very cold temperatures of T {sub dust} < 20 K and low bolometric luminosities of 0.15-0.31 L {sub ☉}. The internal luminosities of B1-bN and B1-bS are estimated to be <0.01-0.03 L {sub ☉} and ∼0.1-0.2 L {sub ☉}, respectively. Millimeter interferometric observations have shown that these sources have already formed central compact objects of ∼100 AU sizes. Both B1-bN and B1-bS are driving the CO outflows with low characteristic velocities of ∼2-4 km s{sup –1}. The fractional abundance of H{sup 13}CO{sup +} at the positions of B1-bN and B1-bS is lower than the canonical value by a factor of four to eight. This implies that a significant fraction of CO is depleted onto dust grains in the dense gas surrounding these sources. The observed physical and chemical properties suggest that B1-bN and B1-bS are in an earlier evolutionary stage than most of the known class 0 protostars. In particular, the properties of B1-bN agree with those of the first hydrostatic core predicted by the MHD simulations. The CO outflow was also detected in the mid-IR source located at ∼15'' from B1-bS. Since the dust continuum emission was not detected in this source, the circumstellar material surrounding this source is less than 0.01 M {sub ☉}. It is likely that the envelope of this source was dissipated by the outflow from the protostar that is located to the southwest of B1-b.