The Interstellar Medium toward the Galactic Center Source 2MASS J17470898-2829561

Abstract

We describe and discuss remarkable infrared spectra, covering key portions of the $2-5$ $\mu$m wavelength interval, of the probable OH/IR supergiant 2MASS J17470898$-$2829561 (2M1747), located in direction of the Sgr B molecular cloud complex within the Central Molecular Zone (CMZ) of the Galaxy. This star was originally singled out for examination based on its suitability for spectroscopy of lines of H${}_3^{+}$ in the CMZ. Analysis of the spectra shows that 2M1747 is deeply embedded within Sgr B1, with A${}_V$ $\gtrsim$ 100 mag, making it the only star within Sgr B for which infrared spectra have been obtained at present, and thereby a unique infrared probe of the dense interstellar medium within the CMZ. Despite the high extinction, spectra of 2M1747 reveal a veiled photosphere in the $K$ band and circumstellar gas in the $M$ band, giving clues as to its nature. Its $3.5-4.0$ $\mu$m spectrum contains the strongest absorption lines of H${}_3^{+}$ observed toward any object to date. The $4.5-4.8$ $\mu$m spectrum has impressively deep and wide absorption lines of interstellar CO, most of which arise in dense gas within Sgr B1. The $3-5$ $\mu$m spectrum also contains several solid state absorption features, which are characteristic of both dense and diffuse clouds, and which raise questions about the identifications of some of these features. We discuss the nature of the star, the extinction to it, the extinction law for dust in the CMZ, and the identifications of the various solid-state features and where they are produced along this complex line of sight.

arXiv comment17 pages, 10 figures; accepted by ApJ 2021 March 10

References in corpus (36)

• Observations of the Icy Universe
• The Optical to Mid-Infrared Extinction Law Based on the APOGEE, Gaia DR2, Pan-STARRS1, SDSS, APASS, 2MASS and WISE Surveys
• Rotational quenching of CO due to H${}_2$ collisions
• The Composition and Distribution of Dust Along the Line of Sight Towards the Galactic Center
• The relation between gas and dust in the Taurus Molecular Cloud
• Line derived infrared extinction towards the Galactic Center
• A 3-5 micron VLT spectroscopic survey of embedded young low mass stars I: Structure of the CO ice
• Hot and Diffuse Clouds near the Galactic Center Probed by Metastable H3+
• Star formation rates and efficiencies in the Galactic Centre
• New Three Micron Spectra of Young Stellar Objects with H_2O Ice Bands
• VLT-CRIRES Survey of Rovibrational CO Emission from Protoplanetary Disks
• The Bolocam Galactic Plane Survey IV: 1.1 and 0.35 mm Dust Continuum Emission in the Galactic Center Region
• Origin of the 6.85 micron band near young stellar objects: The ammonium ion (NH4+) revisited
• A Study of Absorption Features in the Three Micron Spectra of Molecular Cloud Sources with H${}_2$O Ice Bands
• Absorption Line Survey of H3+ toward the Galactic Center Sources II. Eight Infrared Sources within 30 pc of the Galactic Center
• Physical conditions in the central molecular zone inferred by H3+
• Point Sources from a Spitzer IRAC Survey of the Galactic Center
• Heavy ion irradiation of crystalline water ice
• The Central 300 pc of the Galaxy probed by infrared spectra of H${}_3^{+}$ and CO: part I. Predominance of warm and diffuse gas and high H${}_2$ ionization rate
• A New 3.25 Micron Absorption Feature toward Mon R2/IRS-3
• Submillimeter continuum observations of Sagittarius B2 at subarcsecond spatial resolution
• Infrared H3+ and CO Studies of the Galactic Core: GCIRS 3 and GCIRS 1W
• A High-Resolution Survey of HI Absorption toward the Central 200 pc of the Galactic Center
• Cold H2O and CO ice and gas toward the Galactic Center
• Dust Embedded Sources at the Galactic Center. 2 to 4$\mu$m imaging and spectroscopy in the central parsec
• The period-luminosity relation of red supergiants with Gaia DR2
• Two New and Remarkable Sightlines through the Galactic Center's Molecular Gas
• Absorption Line Survey of H3+ toward the Galactic Center Sources III. Extent of the Warm and Diffuse Clouds
• H2, CO, and Dust Absorption through Cold Molecular Clouds
• Laboratory Determination of the Infrared Band Strengths of Pyrene Frozen in Water Ice: Implications for the Composition of Interstellar Ices
• M-Band Spectra of Dust Embedded Sources at the Galactic Center
• Background Infrared Sources for Studying the Galactic Center's Interstellar Gas
• The 200-pc Molecular Cylinder in the Galactic Centre
• The Central 300 pc of the Galaxy probed by infrared spectra of H3+ and CO: II. Expansion and morphology of the warm diffuse gas
• High-spectral resolution M-band observations of CO Rot-Vib absorption lines towards the Galactic center
• Interstellar Extinction Law toward the Galactic Center IV: J, H, and Ks Bands from VVV Red Clump Stars

Cited by in corpus (3)

• Massive Young Stellar Objects in the Galactic Center. II. Seeing Through the Ice-rich Envelopes
• Mapping the aliphatic hydrocarbon content of interstellar dust in the Galactic plane
• The Central 300 pc of the Galaxy Probed by Infrared Spectra of H${}_3^{+}$ and CO: III. Locations of Sgr B2 and Star $\iota$