8/31/2023 0 Comments Spectra 1 part2001 see their Figure 1) has an estimated H 2 mass fraction of. 2001) located in the more diffuse part of LLIV at lower Galactic latitudes not analyzed here (Richter et al. Absorption lines toward PG 0804+761 (Richter et al. ( 2003) report a relatively high detection rate of H 2 in the IVC gas, implying that CNM is ubiquitous, consistent with a key finding of our paper. Wakker ( 2001) constrain the distance to be in the range 0.9–1.8 kpc ( z = 0.6–1.2 kpc). There is thermal dust emission morphologically correlated with the IVC gas in LLIV (Planck Collaboration et al. Absorption of Fe and Si against the AGN PG 0804+761 at ( ℓ, b) = (138 3, 31 0) indicates some depletion onto dust grains (Richter et al. Higher resolution N H I maps of LLIV substructures are shown in Figures 12(b) and 16 of Wakker ( 2001), in the velocity range −60 km s −1 < v < −30 km s −1 and −70 km s −1 < v < −30 km s −1, respectively.Ībundance measurements by Wakker ( 2001) using lines of S ii, N i, and O i indicate a metallicity that is approximately solar. LLIV1 has an approximate size of about 10° in the sky and is connected to other substructures through more extended gas with lower N H I (about 10 19 cm −2 in the velocity range −60 km s −1 < v < −30 km s −1). ![]() These substructures (or "clumps") were cataloged by Kuntz & Danly ( 1996) based on high H i column density ( N H I) contours in the IVC range from data from the Bell Laboratories H i survey at 2° resolution (Stark et al. This IVC gas is part of the low-latitude intermediate-velocity Arch (LLIV) studied by Kuntz & Danly ( 1996), in the particular substructure low-latitude intermediate-velocity Arch 1 (LLIV1 see their Figure 2). We have surveyed and analyzed the properties of H i line emission in an intermediate latitude field in Ursa Major (( ℓ, b) = (143 6, 40 1) or ( α, δ) = (09 h ), focusing on the thermal condensation of warm neutral medium gas (WNM) to cold neutral medium gas (CNM) in the intermediate velocity component (IVC). Our spatially resolved map of the cold gas mass fraction in LLIV1 from DHIGLS reveals significant variations spanning the possible range of f, with a mean and standard deviation of 0.33 and 0.19, respectively. The angular power spectrum of the cold phase is slightly shallower than that of the warm phase, quantifying that the cold phases have relatively more structure on small scales. ![]() These substructures follow the orientation of the overall large-scale cloud, along the diagonal of the GHIGLS field from northwest to southeast (in Galactic coordinates). ![]() The cold phase of LLIV1 appears as a collection of elongated filaments that forms a closed structure within the field decomposed. Similar to the absorption line modeling against 4C +66.09, our best emission line decomposition model has no unstable gas across the whole field of view, suggesting that the thermal condensation and phase transition are not ongoing but rather have reached an equilibrium state. From the latter, we found spin temperature T s ∼ 75 K, cold gas mass fraction f ∼ 0.5, and turbulent sonic Mach number M t ∼ 3.4. The spectral decomposition code ROHSA was used to model the column density of different thermal phases and also to analyze an absorption measurement against the radio source 4C +66.09. This was accomplished using archival H i emission and absorption data from two 21 cm line surveys: GHIGLS at 9 4 resolution and DHIGLS at resolution. We have analyzed the thermal and turbulent properties of the low-latitude intermediate-velocity Arch 1 (LLIV1).
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