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Title: The Molecular Structures of the Local Arm and Perseus Arm in the Galactic Region of l  = [139.°75, 149.°75], b  = [−5.°25, 5.°25]

Abstract

Using the Purple Mountain Observatory Delingha (PMODLH) 13.7 m telescope, we report a 96 deg{sup 2} {sup 12}CO/{sup 13}CO/C{sup 18}O mapping observation toward the Galactic region of l  = [139.°75,149.°75], b  = [−5.°25, 5.°25]. The molecular structures of the Local Arm and Perseus Arm are presented. Combining H i data and part of the Outer Arm results, we obtain that the warp structure of both atomic and molecular gas is obvious, while the flare structure only exists in atomic gas in this observing region. In addition, five filamentary giant molecular clouds on the Perseus Arm are identified. Among them, four are newly identified. Their relations with the Milky Way large-scale structure are discussed.

Authors:
; ; ;  [1]
  1. Purple Mountain Observatory, Chinese Academy of Science, Nanjing 210008 (China)
Publication Date:
OSTI Identifier:
22661213
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal, Supplement Series; Journal Volume: 229; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; CLOUDS; HYDROGEN; MAPPING; MILKY WAY; MOLECULAR STRUCTURE; MOLECULES; STELLAR FLARES; TELESCOPES

Citation Formats

Du, Xinyu, Xu, Ye, Yang, Ji, and Sun, Yan, E-mail: xydu@pmo.ac.cn, E-mail: xuye@pmo.ac.cn. The Molecular Structures of the Local Arm and Perseus Arm in the Galactic Region of l  = [139.°75, 149.°75], b  = [−5.°25, 5.°25]. United States: N. p., 2017. Web. doi:10.3847/1538-4365/AA5D9D.
Du, Xinyu, Xu, Ye, Yang, Ji, & Sun, Yan, E-mail: xydu@pmo.ac.cn, E-mail: xuye@pmo.ac.cn. The Molecular Structures of the Local Arm and Perseus Arm in the Galactic Region of l  = [139.°75, 149.°75], b  = [−5.°25, 5.°25]. United States. doi:10.3847/1538-4365/AA5D9D.
Du, Xinyu, Xu, Ye, Yang, Ji, and Sun, Yan, E-mail: xydu@pmo.ac.cn, E-mail: xuye@pmo.ac.cn. Sat . "The Molecular Structures of the Local Arm and Perseus Arm in the Galactic Region of l  = [139.°75, 149.°75], b  = [−5.°25, 5.°25]". United States. doi:10.3847/1538-4365/AA5D9D.
@article{osti_22661213,
title = {The Molecular Structures of the Local Arm and Perseus Arm in the Galactic Region of l  = [139.°75, 149.°75], b  = [−5.°25, 5.°25]},
author = {Du, Xinyu and Xu, Ye and Yang, Ji and Sun, Yan, E-mail: xydu@pmo.ac.cn, E-mail: xuye@pmo.ac.cn},
abstractNote = {Using the Purple Mountain Observatory Delingha (PMODLH) 13.7 m telescope, we report a 96 deg{sup 2} {sup 12}CO/{sup 13}CO/C{sup 18}O mapping observation toward the Galactic region of l  = [139.°75,149.°75], b  = [−5.°25, 5.°25]. The molecular structures of the Local Arm and Perseus Arm are presented. Combining H i data and part of the Outer Arm results, we obtain that the warp structure of both atomic and molecular gas is obvious, while the flare structure only exists in atomic gas in this observing region. In addition, five filamentary giant molecular clouds on the Perseus Arm are identified. Among them, four are newly identified. Their relations with the Milky Way large-scale structure are discussed.},
doi = {10.3847/1538-4365/AA5D9D},
journal = {Astrophysical Journal, Supplement Series},
number = 2,
volume = 229,
place = {United States},
year = {Sat Apr 01 00:00:00 EDT 2017},
month = {Sat Apr 01 00:00:00 EDT 2017}
}
  • We present the results of an unbiased CO survey in the Galactic range of 34.°75 ≤  l  ≤ 45.°25 and −5.°25 ≤  b  ≤ 5.°25, and the velocity range beyond the Outer arm. A total of 168 molecular clouds (MCs) are identified within the Extreme Outer Galaxy (EOG) region, and 31 of these MCs are associated with {sup 13}CO  emission. However, none of them show significant C{sup 18}O  emission under the current detection limit. The typical size and mass of these MCs are 5 pc and 3 × 10{sup 3} M {sub ⊙}, implying a lack of large and massive MCs in the EOG region. Similar to MCsmore » in the outer Galaxy, the velocity dispersions of EOG clouds are also correlated with their sizes; however, they are well displaced below the scaling relationship defined by the inner Galaxy MCs. These MCs with a median Galactocentric radius of 12.6 kpc show very different distributions from those of the MCs in the Outer arm published in our previous paper, while roughly following the Outer Scutum–Centaurus arm defined by Dame and Thaddeus. This result may provide robust evidence for the existence of the Outer Scutum–Centaurus arm. The lower limit of the total mass of this segment is about 2.7 × 10{sup 5} M {sub ⊙}, which is about one magnitude lower than that of the Outer arm. The mean thickness of the gaseous disk is about 1.°45 or 450 pc, and the scale height is about 1.°27, or 400 pc above the b  = 0° plane. The warp traced by CO emission is very obvious in the EOG region and its amplitude is consistent with the predictions by other warp models using different tracers, such as dust, H i, and stellar components of our Galaxy.« less
  • The results from deep spectrophotometry of four Perseus arm H II regions (NGC 1624, NGC 2359, NGC 7538, and NGC 7635) obtained with the KPNO IIDS are presented. The observed line strengths are used to derive electron temperatures, densities, and the relative concentrations of H, He, N, O, S, Cl, and Ar in the nebulae. These abundances are combined with others from the literature and are used to estimate the magnitude of galactic abundance gradients over the 8--14 kpc region of the solar neighborhood.Significant radial gradients for oxygen and nitrogen are found: d log (O/H)/dR=-0.059 +- 0.017 kpc/sup -1/ andmore » d log (N/H)/dR= -0.083 +- 0.018 kpc/sup -1/, while only marginal evidence for a helium gradient is found: d log (He/H)/dR=-0.008 +- 0.008 kpc/sup -1/. Little evidence for gradient in S/H is found. From the red (N II) and (S II) lines we found d log (N/sup +//S/sup +/)/dR=-0.068 +- 0.024 kpc/sup -1/, which suggests that a radial gradient in S/O exists in the Galaxy. The O/H gradient found in this study is similar to that found from planetary nebulae, while the N/H gradient is significantly smaller. These results suggest that most of the nitrogen in the interstellar medium of the Galaxy was produced by primary nucleosynthesis processes.We also find evidence that the radial O/H and N/H gradients for H II regions in a given spiral arm are 2 to 3 times steeper than the global gradients over the 8--14 kpc interval in galactocentric distance. For four H II regions in the Sagittarius arm we found d log (O/H)/dR=-0.24 kpc/sup -1/ and d log (N/H)/dR=-0.16 kpc/sup -1/. For five H II regions in the Perseus arm we found d log (O/H)/dR=-0.18 kpc/sup -1/ and d log (N/H)/dR=-0.15 kpc/sup -1/. The larger magnitudes of these gradients are greater than those of the global gradients by amounts which exceed reasonable errors in abundances and/or the relative distances for the individual H II regions.« less
  • The evolution of magnetic properties and local atomic ordering during thermal annealing has been studied for amorphous Fe{sub 75}Ni{sub 5}B{sub 15}Si{sub 5} thin films. Resistivity, vibrating sample magnetometer (VSM), ferromagnetic resonance (FMR), extended x-ray absorption fine structure (EXAFS), and Moessbauer effect (ME) measurements were taken on samples annealed at various temperatures ranging to film crystallization. The as-deposited samples are in a close-packed structure with little short-range order. Samples annealed above 200 {degree}C show ordering of the boron shell, but no indication of long-range ordering. With the exception of the anisotropy and coercive fields, no change in the magnetic or microwavemore » magnetic parameters is observed for these samples prior to crystallization. Samples annealed above 400 {degree}C show indications of crystallization for all measurements.« less
  • A 3-sq deg section of the inner Galactic plane centered at l = 24 deg, b = 0 deg in both (C-13)O and CS. The observations were supplemented by preexisting CO data from the Massachusetts-Stony Brook Galactic plane survey. It was possible to identify 47 molecular clouds in the region surveyed. Distances to the clouds were assigned using a size-line width relation which was derived for a set of calibrator clouds at known distances. By combining the CO and (C-13)O data, it was possible to calculate LTE masses for the clouds and to compare them with masses estimated from themore » virial theorem. Masses estimated from the two methods are tightly correlated, suggesting that the clouds observed in this study are close to virial equilibrium. The masses derived using the two methods are in reasonable agreement. Little CS emission was detected in this section or the Galactic plane; averaged over the region of the survey, the CO/CS integrated intensity ratio is found to be 660 + or - 160, considerably larger than the ratio in the Galactic center. 26 refs.« less