Kuiper Widefield Infrared Camera Far‐Infrared Imaging of the Galactic Center: The Circumnuclear Disk Revealed

Citations Over TimeTop 17% of 1999 papers

Abstract

We present images of the Galactic center in the dust continuum at 31.5 and 37.7 μm obtained with the Kuiper Widefield Infrared Camera on the Kuiper Airborne Observatory. The raw images have a spatial resolution of ~85 and cover a region roughly 10' (R.A.) by 24' (decl.) in extent. Here we discuss the innermost 28 × 36 (6.9 × 9.1 pc) regions roughly centered on Sagittarius A*, where the high signal-to-noise ratio permits image restoration to ~36-57 spatial resolution at 31.5 and 37.7 μm, respectively. These images clearly delineate the warm dust in the but also show an elliptical structure centered on Sgr A* and intersecting the minispiral at the western arc that we identify as the photodissociated inner rim of the circumnuclear disk (CND) or ring. This is the first image of the complete disk and the first image of both the minispiral and CND in a single tracer, thereby permitting detailed studies of the intimate association between these two structures. The 31.5/37.7 μm color temperature map indicates that most of the far-UV flux required to heat the dust grains must come from centrally located sources. The cluster of He I emission-line stars recently identified near Sgr A* is sufficient to provide half the heating for the far-IR ring and minispiral structures, the balance likely being provided by O and B stars associated with the cluster. We also find ~16 color temperature peaks distributed within the CND that we suggest are the locations of early type (B4 to O9) main-sequence stars. To match the observed far-IR fluxes from the ring, we require an unusually high 30-40 μm dust grain emissivity and/or an usually high UV albedo. The far-IR morphology is reproduced by a simple model: an inclined (i ~ 65°), slightly elliptical (e ~ 0.06) torus with one focus at Sgr A* and two streamers on parabolic orbits with foci at Sgr A*. The torus has an inner radius of 1.58 pc, is ~0.4 pc thick, and consists of clumpy cloudlets with characteristic sizes less than 0.15 pc. The northern streamer is identified with the northern arm, and the east-west (EW) streamer is identified with the bar and eastern arm structures seen in both their [Ne II] fine-structure line emission and the radio continuum. The northern arm is traced in the far-IR continuum from regions ~1.4 pc outside of the far-IR ring to its apparent intersection with the EW streamer. The eastern CND is not detected in the radio continuum because of extinction by the intervening northern arm, which therefore must be nearly in the plane of the CND. Extensions of the EW streamer outside of the CND are apparent to the east and especially to the northwest. The EW streamer lies ~85° out of the plane of the CND and is on a parobolic orbit focused on Sgr A* at a distance of 0.33 pc, with its apex well in front of or behind Sgr A*.

Related Papers

• → Astronomical Measurements in the Infrared(1966)876 cited
• → Sagittarius A* High-energy X-Ray Flare Properties during NuStar Monitoring of the Galactic Center from 2012 to 2015(2017)29 cited
• → The capabilities of isophot to detect the infrared extragalactic background radiation(1991)
• → ISIS IR : The First Infrared Fibre-Fed Spectrograph(1994)
• → Some Quantitative Aspects of Galactic and Extragalactic Infrared Astronomy(2007)