Opening the Treasure Chest in Carina

Abstract

We have mapped the G287.84-0.82 cometary globule (with the Treasure Chest cluster embedded in it) in the South Pillars region of Carina (i) in [C ii], 63 µm [O i] , and CO(11-10) using the heterodyne receiver array upGREAT on SOFIA and (ii) in J=2-1 transitions of CO, 13 CO, C 18 O and J=3-2 transitions of H 2 CO using the APEX telescope in Chile. We use these data to probe the morphology, kinematics, and physical conditions of the molecular gas and the photon dominated regions (PDRs) in G287.84-0.82. The velocity-resolved observations of [C ii] and [O i] suggest that the overall structure of the pillar (with red-shifted photo evaporating tails) is consistent with the effect of FUV radiation and winds from η Car and O stars in Trumpler 16. The gas in the head of the pillar is strongly influenced by the embedded cluster, whose brightest member is an O9.5 V star, CPD -59 • 2661. The emission of the [C ii] and [O i] lines peak at a position close to the embedded star, while all the other tracers peak at another position lying to the north-east consistent with gas being compressed by the expanding PDR created by the embedded cluster. The molecular gas inside the globule is probed with the J=2-1 transitions of CO and isotopologues as well as H 2 CO, and analyzed using a non-LTE model (escape-probability approach), while we use PDR models to derive the physical conditions of the PDR. We identify at least two PDR gas components; the diffuse part (∼10 4 cm −3 ) is traced by [C ii], while the dense (n ∼2-8 10 5 cm −3 ) part is traced by [C ii], [O i], CO(11-10). Using the the F=2-1 transition of [ 13 C ii] detected at 50 positions in the region, we derive optical depths (0.9-5), excitation temperatures of [C ii] (80-255 K), and N(C + ) of 0.3-1×10 19 cm −2 . The total mass of the globule is ∼ 1,000 M ⊙ , about half of which is traced by [C ii]. The dense PDR gas has a thermal pressure of 10 7 -10 8 K cm −3 , which is similar to the values observed in other regions.

The distribution of ionized, atomic and PDR gas around S1 in Rho Ophiuchus

“…The [C ii] spectra show the self-absorption dips even far to the east and the rarer isotope 13 C + has been detected at a large number of positions, suggesting an N(C + )∼ of a few times 10 18 cm −2 over an extended region. The estimated N(C + ) lie within the typical range of values between 10 18 -10 19 cm −2 that is found in Galactic PDRs (Ossenkopf et al 2013;Mookerjea et al 2019). The H 2 column density estimated from dust continuum emission maps range between 1-2.5 10 22 cm −2 at these positions.…”

HII regions and high-mass starless clump candidates II. Fragmentation and induced star formation at ~0.025 pc scale: An ALMA continuum study

“…Recent studies show that H 2 CO mainly traces denser and warmer gas ( 30 K, ∼ 10 5 cm −3 ), such as warm gas in OMC-1 (Tang et al 2018) and cometary globule (bright-rimmed cloud impacted by H ii regions, Mookerjea et al 2019). The detection of H 2 CO is also related to shock chemistry corresponding to outflow (Contreras et al 2018;Gieser et al 2019).…”

On the compressive nature of turbulence driven by ionising feedback in the pillars of the Carina Nebula

“…Pillar 8 as we characterise in this study is part of the extensively studied dust pillar G287.84-0.82. It has a dense compact cluster embedded in its head, which is contributing to the local dynamic and thermodynamic state of the pillar (Smith et al 2005;Hartigan et al 2015;Mookerjea et al 2019). This cluster, "Treasure Chest" as coined by Smith et al (2005), contains more than 69 young stars, including at least one O-star (e.g.…”

“…This cluster, "Treasure Chest" as coined by Smith et al (2005), contains more than 69 young stars, including at least one O-star (e.g. ; Hägele et al 2004), illuminating its own compact H region seen in H𝛼 and in typical photondominated region (PDR) line emissions (Thackeray 1950;Smith et al 2005;Mookerjea et al 2019). While this cluster influences the PDR and molecular gas dynamics of pillar 8, the overall structure is consistent with it being shaped by the feedback from 𝜂Car and the Trumpler 16 cluster.…”

“…That being said, the influence of the Treasure chest on the local gas column density and effectively on 𝑏 is evident. Mookerjea et al (2019) showed that a PDR is formed internally in pillar 8, primarily due to feedback from the Treasure Chest. Additionally, they observe a peak in dust emission and the high density line emissions traced with isotopologues of CO, which are spatially slightly offset from the peak in PDR tracer emission.…”