Infrared H{sub 3}{sup +} and CO studies of the galactic core: GCIRS 3 and GCIRS 1W

Journal Article · Sat May 10 04:00:00 EDT 2014 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/786/2/96· OSTI ID:22356958

Goto, Miwa ^[1]; Geballe, T. R. ^[2]; Indriolo, Nick ^[3]; Yusef-Zadeh, Farhad ^[4]; Usuda, Tomonori ^[5]; Henning, Thomas ^[6]; Oka, Takeshi ^[7]

---

1. Universitäts-Sternwarte München, Scheinerstr. 1, D-81679 Munich (Germany)
2. Gemini Observatory, 670 North A'ohoku Place, Hilo, HI 96720 (United States)
3. Department of Physics and Astronomy, Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218 (United States)
4. Department of Physics and Astronomy, Northwestern University, Evanston, IL 60208 (United States)
5. Subaru Telescope, 650 North A'ohoku Place, Hilo, HI 96720 (United States)
6. Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg (Germany)
7. Department of Astronomy and Astrophysics, Department of Chemistry, and Enrico Fermi Institute, University of Chicago, Chicago, IL 60637 (United States)

We have obtained improved spectra of key fundamental band lines of H{sub 3}{sup +}, R(1, 1) {sup l}, R(3, 3) {sup l}, and R(2, 2) {sup l}, and ro-vibrational transitions of CO on sightlines toward the luminous infrared sources GCIRS 3 and GCIRS 1W, each located in the Central Cluster of the Galactic center within several arcseconds of Sgr A*. The spectra reveal absorption occurring in three kinds of gaseous environments: (1) cold dense and diffuse gas associated with foreground spiral/lateral arms; (2) warm and diffuse gas absorbing over a wide and mostly negative velocity range, which appears to fill a significant fraction of the Galaxy's Central Molecular Zone (CMZ); and (3) warm, dense and compact clouds with velocities near +50 km s{sup –1} probably within 1-2 pc of the center. The absorptions by the first two cloud types are nearly identical for all the sources in the Central Cluster, and are similar to those previously observed on sightlines from Sgr A* to 30 pc east of it. Cloud type (3), which has only been observed toward the Central Cluster, shows distinct differences between the sightlines to GCIRS 3 and GCIRS 1W, which are separated on the sky by only 0.33 pc in projection. We identify this material as part of an inward extension of the circumnuclear disk previously known from HCN mapping. Lower limits on the products of the hydrogen ionization rate ζ and the path length L are 2.3 × 10{sup 5} cm s{sup –1} and 1.5 × 10{sup 3} cm s{sup –1} for the warm and diffuse CMZ gas and for the warm and dense clouds in the core, respectively. The limits indicate that the ionization rates in these regions are well above 10{sup –15} s{sup –1}.

• OSTI ID: 22356958
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 786; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ABSORPTION
CARBON MONOXIDE
GALAXIES
GALAXY NUCLEI
HYDROGEN
MOLECULAR IONS
MOLECULES
SPECTRA
STARS
VELOCITY