skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: STRUCTURAL VARIATION OF MOLECULAR GAS IN THE SAGITTARIUS ARM AND INTERARM REGIONS

Abstract

We have carried out survey observations toward the Galactic plane at l Almost-Equal-To 38 Degree-Sign in the {sup 12}CO and {sup 13}CO J = 1-0 lines using the Nobeyama Radio Observatory 45 m telescope. A wide area (0.{sup 0}8 Multiplication-Sign 0.{sup 0}8) was mapped with high spatial resolution (17''). The line of sight samples the gas in both the Sagittarius arm and the interarm regions. The present observations reveal how the structure and physical conditions vary across a spiral arm. We classify the molecular gas in the line of sight into two distinct components based on its appearance: the bright and compact B component and the fainter and diffuse (i.e., more extended) D component. The B component is predominantly seen at the spiral arm velocities, while the D component dominates at the interarm velocities and is also found at the spiral arm velocities. We introduce the brightness distribution function and the brightness distribution index (BDI, which indicates the dominance of the B component) in order to quantify the map's appearance. The radial velocities of BDI peaks coincide with those of high {sup 12}CO J = 3-2/{sup 12}CO J = 1-0 intensity ratio (i.e., warm gas) and H II regions, andmore » tend to be offset from the line brightness peaks at lower velocities (i.e., presumably downstream side of the arm). Our observations reveal that the gas structure at small scales changes across a spiral arm: bright and spatially confined structures develop in a spiral arm, leading to star formation at the downstream side, while extended emission dominates in the interarm region.« less

Authors:
; ;  [1];  [2];  [3]
  1. Joint ALMA Office, Alonso de Cordova 3107, Vitacura, Santiago 763-0355 (Chile)
  2. Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794-3800 (United States)
  3. Department of Physics, Faculty of Science, Kagoshima University, 1-21-35 Korimoto, Kagoshima 890-0065 (Japan)
Publication Date:
OSTI Identifier:
22037024
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 752; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ASTROPHYSICS; BRIGHTNESS; DISTRIBUTION FUNCTIONS; GALAXIES; INDEXES; MOLECULES; PHOTON EMISSION; RADIAL VELOCITY; RADIOASTRONOMY; SPATIAL RESOLUTION; STARS; VARIATIONS

Citation Formats

Sawada, Tsuyoshi, Hasegawa, Tetsuo, Sugimoto, Masahiro, Koda, Jin, and Handa, Toshihiro, E-mail: sawada.tsuyoshi@nao.ac.jp. STRUCTURAL VARIATION OF MOLECULAR GAS IN THE SAGITTARIUS ARM AND INTERARM REGIONS. United States: N. p., 2012. Web. doi:10.1088/0004-637X/752/2/118.
Sawada, Tsuyoshi, Hasegawa, Tetsuo, Sugimoto, Masahiro, Koda, Jin, & Handa, Toshihiro, E-mail: sawada.tsuyoshi@nao.ac.jp. STRUCTURAL VARIATION OF MOLECULAR GAS IN THE SAGITTARIUS ARM AND INTERARM REGIONS. United States. doi:10.1088/0004-637X/752/2/118.
Sawada, Tsuyoshi, Hasegawa, Tetsuo, Sugimoto, Masahiro, Koda, Jin, and Handa, Toshihiro, E-mail: sawada.tsuyoshi@nao.ac.jp. Wed . "STRUCTURAL VARIATION OF MOLECULAR GAS IN THE SAGITTARIUS ARM AND INTERARM REGIONS". United States. doi:10.1088/0004-637X/752/2/118.
@article{osti_22037024,
title = {STRUCTURAL VARIATION OF MOLECULAR GAS IN THE SAGITTARIUS ARM AND INTERARM REGIONS},
author = {Sawada, Tsuyoshi and Hasegawa, Tetsuo and Sugimoto, Masahiro and Koda, Jin and Handa, Toshihiro, E-mail: sawada.tsuyoshi@nao.ac.jp},
abstractNote = {We have carried out survey observations toward the Galactic plane at l Almost-Equal-To 38 Degree-Sign in the {sup 12}CO and {sup 13}CO J = 1-0 lines using the Nobeyama Radio Observatory 45 m telescope. A wide area (0.{sup 0}8 Multiplication-Sign 0.{sup 0}8) was mapped with high spatial resolution (17''). The line of sight samples the gas in both the Sagittarius arm and the interarm regions. The present observations reveal how the structure and physical conditions vary across a spiral arm. We classify the molecular gas in the line of sight into two distinct components based on its appearance: the bright and compact B component and the fainter and diffuse (i.e., more extended) D component. The B component is predominantly seen at the spiral arm velocities, while the D component dominates at the interarm velocities and is also found at the spiral arm velocities. We introduce the brightness distribution function and the brightness distribution index (BDI, which indicates the dominance of the B component) in order to quantify the map's appearance. The radial velocities of BDI peaks coincide with those of high {sup 12}CO J = 3-2/{sup 12}CO J = 1-0 intensity ratio (i.e., warm gas) and H II regions, and tend to be offset from the line brightness peaks at lower velocities (i.e., presumably downstream side of the arm). Our observations reveal that the gas structure at small scales changes across a spiral arm: bright and spatially confined structures develop in a spiral arm, leading to star formation at the downstream side, while extended emission dominates in the interarm region.},
doi = {10.1088/0004-637X/752/2/118},
journal = {Astrophysical Journal},
issn = {0004-637X},
number = 2,
volume = 752,
place = {United States},
year = {2012},
month = {6}
}