TWO EXTREME YOUNG OBJECTS IN BARNARD 1-b

Abstract

Two submm/mm sources in the Barnard 1b (B1-b) core, B1-bN and B1-bS, have been studied in dust continuum, H 13 CO + J=1-0, CO J=2-1, 13 CO J=2-1, and C 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 dust < 20 K and low bolometric luminosities of 0.15-0.31 L ⊙ . The internal luminosities of B1-bN and B1-bS are estimated to be <0.01-0.03 L ⊙ and ∼0.1-0.2 L ⊙ , 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 −1 . The fractional abundance of H 13 CO + at the positions of B1-bN and B1-bS is lower than the canonical value by a factor of 4-8. This implies that significant fraction of CO is depleted onto dust grains in dense gas surrounding these sources. The observed physical and chemical properties suggest that B1-bN and B1-bS are in the earlier evolutionary stage than most of the known Class 0 protostars. Especially, 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 ⊙ . 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.

Nascent bipolar outflows associated with the first hydrostatic core candidates Barnard 1b-N and 1b-S

“…B.1 the SED of B1b-N and B1b-S and provide refined positions in Table B.1. The measured continuum fluxes agree well with the values reported by Pezzuto et al (2012) and Hirano & Liu (2014). It is interesting to observe that B1b-S is more luminous than B1b-N at far-infrared and submillimeter wavelengths while the reverse is true long-ward of ∼2.5 mm.…”

“…B1b-W is associated with a secondary peak of the H 2 CO and CH 3 OH emission, with narrow line profiles. We did not detect any high-velocity emission that might be associated with B1b-W or with the high-velocity CO knot detected by Hirano & Liu (2014). The region between B1b-N and B1b-S presents lower CH 3 OH emission despite the high dust column density (Daniel et al 2013), a behavior characteristic of depletions due to freezing of molecules onto grains, and supported by the detection of high column densities of ices including CH 3 OH towards B1b-W (Boogert et al 2008).…”

“…The agreement of the μ = 2 case with the properties derived for B1b-N, including its short dynamical age, compact size, and cold SED, is excellent, supporting its early evolutionary stage. As already discussed by Hirano & Liu (2014), the more energetic outflow properties, higher luminosity, and warmer SED of B1b-S only poorly fit with the same models, providing further support for the classification of B1b-S as a class 0 YSO, currently in a low accretion stage.…”

“…Following Hirano & Liu (2014), we adopt a distance of 230 pc for Barnard 1, implying that 2 corresponds to ∼500 AU. The observations are presented in Sect.…”

Deuteration of ammonia in the starless core Ophiuchus/H-MM1

“…The interpretation of chemical data from these two, bright sources of deuterated ammonia is complicated by the possibility of enhanced evaporation from grains because of shocks. The Barnard 1 core contains two, albeit very young and low-mass protostars driving outflows (B1-bS and B1-bN; Hatchell et al 2007;Hirano & Liu 2014;Gerin et al 2015). The core in L1689N may be compressed by an outlow from the adjacent protostellar source IRAS 16293-2422 (Lis et al 2002a;Stark et al 2004;Gerin et al 2006).…”