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Abstract We present a catalog of clouds identified from the12CO (1–0) data of M83, which was observed using the Atacama Large Millimeter/submillimeter Array with a spatial resolution of ∼46 pc and a mass sensitivity of ∼104M⊙(3σ). The almost full-disk coverage and high sensitivity of the data allowed us to sample 5724 molecular clouds with a median mass of ∼1.9 × 105M⊙, which is comparable to the most frequently sampled mass of giant molecular clouds by surveys in the Milky Way (MW). About 60% of the total CO luminosity in M83's disk arises from clouds more massive than 106M⊙. Such massive clouds comprise 16% of the total clouds in number and tend to concentrate toward the arm, bar, and center, while smaller clouds are more prevalent in interarm regions. Most >106M⊙clouds have peak brightness temperaturesTpeakabove 2 K with the current resolution. Comparing the observed cloud properties with the scaling relations determined by P. M. Solomon et al. (1987, hereafter S87),Tpeak> 2 K clouds follow the relations, butTpeak< 2 K clouds, which are dominant in number, deviate significantly. Without considering the effect of beam dilution, the deviations would suggest modestly high virial parameters (medianαvir∼ 2.7) and low surface mass densities (median Σ ∼ 22M⊙pc−2) for the entire cloud samples, which are similar to values found for the MW clouds by T. S. Rice et al. (2016) and M.-A Miville-Deschênes et al. (2017). However, once beam dilution is taken into account, the observedαvirand Σ for a majority of the clouds (mostlyTpeak<2 K) can be potentially explained with intrinsic Σ of ∼100M⊙pc−2andαvirof ∼1, which are similar to the clouds of S87.
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Galactic Mass Estimates Using Dwarf Galaxies as Kinematic Tracers
Abstract New mass estimates and cumulative mass profiles with Bayesian credible regions for the Milky Way (MW) are found using the Galactic Mass Estimator (GME) code and dwarf galaxy (DG) kinematic data from multiple sources. GME takes a hierarchical Bayesian approach to simultaneously estimate the true positions and velocities of the DGs, their velocity anisotropy, and the model parameters for the Galaxy’s total gravitational potential. In this study, we incorporate meaningful prior information from past studies and simulations. The prior distributions for the physical model are informed by the results of Eadie & Jurić, who used globular clusters instead of DGs, as well as by the subhalo distributions of the Ananke Gaia-like surveys from Feedback in Realistic Environments-2 cosmological simulations (see Sanderson et al.). Using DGs beyond 45 kpc, we report median and 95% credible region estimates forr200= 212.8 (191.12, 238.44) kpc, and for the total enclosed massM200= 1.19 (0.87, 1.68) × 1012M⊙(adopting Δc= 200). Median mass estimates at specific radii are also reported (e.g.,M(< 50 kpc) = 0.52 × 1012M⊙andM(100 kpc) = 0.78 × 1012M⊙). Estimates are comparable to other recent studies using Gaia DR2 and DGs, but notably different from the estimates of Eadie & Jurić. We perform a sensitivity analysis to investigate whether individual DGs and/or a more massive Large Magellanic Cloud on the order of 1011M⊙may be affecting our mass estimates. We find possible supporting evidence for the idea that some DGs are affected by a massive LMC and are not in equilibrium with the MW.
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- Award ID(s):
- 2045928
- PAR ID:
- 10361746
- Publisher / Repository:
- DOI PREFIX: 10.3847
- Date Published:
- Journal Name:
- The Astrophysical Journal
- Volume:
- 924
- Issue:
- 2
- ISSN:
- 0004-637X
- Format(s):
- Medium: X Size: Article No. 131
- Size(s):
- Article No. 131
- Sponsoring Org:
- National Science Foundation
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