Central 300 pc of the galaxy probed by the infrared spectra of H3+ and CO part II. Morphology and dynamics of the gas

Oka, Takeshi

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https://hdl.handle.net/2142/100816 Copy

Description

Title

Central 300 pc of the galaxy probed by the infrared spectra of H3+ and CO part II. Morphology and dynamics of the gas

Author(s)

Oka, Takeshi

Contributor(s)

• Indriolo, Nick
• McCall, Benjamin J.
• Usuda, Tomonori
• Goto, Miwa
• Geballe, Thomas R.

Issue Date

2018-06-21

Keyword(s)

Astronomy

Abstract

Velocity-resolved spectra of infrared lines of H+ 3 at 3.7 µm and CO at 2.3 µm have been obtained toward ∼40 stars in the Central Molecular Zone (CMZ), a region of radius ∼150 pc centered on the Galactic center. Although the coverage of the region is limited by the available number of suitable stars for absorption spectroscopy, the rich Doppler profiles of the H + 3 lines in warm (T∼250 K) and diffuse (n ≤100 cm−3 ) cloudsa have allowed us to draw a longitude-velocity (l-v) plot to reach the following conclusions. (1) Based on the blue-shifted profiles of H+ 3 absorption lines, which are dominantly in the velocity range from - 200 km s−1 to 10 km s−1 , the warm diffuse gas is moving outward from the center. (2) Although limited in uniformity of longitudinal coverage, the observed (l-v) plot for H+ 3 suggests that the outer surface of the expanding gas forms a ring of radius of ∼140 pc and has a velocity of expansion of ∼140 km s−1 . This finding revives the idea of the expanding molecule ring proposed by Kaifu et al.(1972)b and Scoville (1972)c which contrasts with a more recent interpretation of the overall gas kinematics as due to a barred gravitational potential (Binney et al. 1991).d (3) The results revive the idea of an explosion or overall expulsion of gas from the center within the last few million years. Unlike the original proposals that the EMR is also rotating, the H+ 3 l-v plot indicates purely expanding gas.

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

text

Language

eng

Permalink

http://hdl.handle.net/2142/100816

DOI

10.15278/isms.2018.RL11

Copyright and License Information

Copyright 2018 Takeshi Oka

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