Probing ISM Structure in Trumpler 14 and Carina I Using the Stratospheric Terahertz Observatory 2

Abstract

We present observations of the Trumpler 14/Carina I region carried out using the Stratospheric Terahertz Observatory 2 (STO2). The Trumpler 14/Carina I region is in the west part of the Carina Nebula Complex, which is one of the most extreme star-forming regions in the Milky Way. We observed Trumpler 14/Carina I in the 158 µm transition of [C ii] with a spatial resolution of 48 and a velocity resolution of 0.17 km s −1 . The observations cover a 0.25 • by 0.28 • area with central position l = 297.34 • , b = -0.60 • . The kinematics show that bright [C ii] structures are spatially and spectrally correlated with the surfaces of CO clouds, tracing the photodissociation region and ionization front of each molecular cloud. Along 7 lines of sight that traverse Tr 14 into the dark ridge to the southwest, we find that the [C ii] luminosity from the HII region is 3.7 times that from the PDR. In same los we find in the PDRs an average ratio of 1:4.1:5.6 for the mass in atomic gas:dark-CO gas: molecular gas traced by CO. Comparing multiple gas tracers including HI 21cm, [C ii], CO, and radio recombination lines, we find that the HII regions of the Carina Nebula Complex are well-described as HII regions with one-side freely expanding towards us, consistent with the champagne model of ionized gas evolution. The dispersal of the GMC in this region is dominated by EUV photoevaporation; the dispersal timescale is 20-30 Myr. Effective Resolution a 55 Pointing Accuracy <15 Spectral Resolution 1 MHz Velocity Resolution 0.17 km s −1 a Angular resolution of the regridded map.This study contains extensive analysis with many new findings. The followings are the highlights of this study and can be found in the discussion and conclusions sections. Comparing our [C ii] spectral map to the Mopra CO map, we found that bright [C ii] emission in the CNC is closely related to the CO clumps in position-position-velocity space, suggesting that bright [C ii] emission likely arises from PDR and ionization fronts. We also found large absorption cavities in HI 21 cm emission and that those cavities are in a good agreement with the CO clouds/clumps and the Keyhole Nebula, a CO-dark molecular cloud, in position-position space. On the other hand, velocities of the absorption cavities are ±5-10 km s −1 shifted from the CO velocity centroids, suggesting that the cavities may follow cold HI gas photoevaporating or stripped from cloud surfaces. Through detailed PDR modeling of 10 different regions representing various ISM structures, we found a mass proportion of 1:4.1:5.6 for the atomic:dark:molecular(CO) gas and that six out of ten regions are dominated by [C ii] emission from HII regions rather than PDRs. Finally, combining kinematics and modelings, we found that the three-dimensional morphology of the CNC is consistent with one side of numerous blister HII regions expanding freely toward us, similar to a champagne flow, with a lifetime of CO clouds exposed to HII regions being 20-30 Myr.We describe details of observations using STO2 and data reduction ...

Effect of Feedback of Massive Stars in the Fragmentation, Distribution, and Kinematics of the Gas in Two Star-forming Regions in the Carina Nebula

“…In a recent paper, Seo et al (2019) observed the 158 µm line of [C II] in the gas nearby Trumpler 14 and the bright H II region Car I using the Stratospheric Terahertz Observatory 2 (STO2). They found that the bright [C II] emission correlates with the surfaces of the CO structures, tracing the photodissociation region (PDR) and the ionizionation fronts in the NC.…”

Photodissociation and X-Ray Dominated Regions

“…Anderson et al (2019) find that the (velocity resolved) [N II] 205 µm emission in S235 is clearly velocity shifted from the [C II] emission and only ∼10% of the [C II] comes from the neutral gas 15 . In contrast, Seo et al (2019) find in the Trumpler 14/Carina region that most of the [C II] comes from the ionized gas along lines of sight that pass through the blister H II region with embedded, high density, neutral cores also contributing.…”

“…The exact density or radiation field strength predicted by the models will vary but they are still good guides for the general physical conditions and dominant physical processes. 33 µm ratio (sensitive to 10 2 ne 10 5 cm −3 ) or from the thermal pressure in the PDR/H II region (e.g., Seo et al 2019). Alternatively, the fraction of [C II] can be determined by comparing the resolved velocity distributions of tracers of the ionized, neutral and molecular gas (e.g., Pineda et al 2013, Anderson et al 2019, Seo et al 2019.…”

“…33 µm ratio (sensitive to 10 2 ne 10 5 cm −3 ) or from the thermal pressure in the PDR/H II region (e.g., Seo et al 2019). Alternatively, the fraction of [C II] can be determined by comparing the resolved velocity distributions of tracers of the ionized, neutral and molecular gas (e.g., Pineda et al 2013, Anderson et al 2019, Seo et al 2019. The fraction of [C II] originating from the ionized gas typically amounts to ∼5-30% and should be subtracted before analysis.…”

“…Velocity resolved line profiles of [C II] and [O I] used in combination with other tracers such as [C I] and CO reveal outflows (e.g., Schneider et al 2018), thermal and non-thermal pressures (e.g., Goicoechea et al 2015, Pérez-Beaupuits et al 2015, multiple PDR components (e.g., Dedes et al 2010, Seo et al 2019, and can separate the neutral and ionized gas. For example, line widths suggest an equipartition of thermal, turbulent, and magnetic pressures in the PDRs associated with the Orion region and RCW 49 (Tiwari et al 2021.…”