Mid-Infrared Observations of the Galactic Center Arc and the Sgr A East HII Region

1989 ◽  
pp. 287-292 ◽  
Author(s):  
F. Yusef-Zadeh ◽  
C. M. Telesco ◽  
R. Decher
Keyword(s):  
Galactic Center ◽  
Mid Infrared ◽  
Hii Region ◽  
Infrared Observations ◽  
Sgr A

scholarly journals Near- and Mid-infrared Observations in the Inner Tenth of a Parsec of the Galactic Center Detection of Proper Motion of a Filament Very Close to Sgr A*

2020 ◽  
Vol 897 (1) ◽  
pp. 28 ◽  
Author(s):  
Florian Peißker ◽  
Andreas Eckart ◽  
Nadeen B. Sabha ◽  
Michal Zajaček ◽  
Harshitha Bhat
Keyword(s):  
Proper Motion ◽  
Galactic Center ◽  
Mid Infrared ◽  
Infrared Observations ◽  
Sgr A

scholarly journals Mid-Infrared (4.8–12.4 and 20.0 μm) Imaging of the Galactic Center: Modeling the Dust Emission and Energetics of the Central Parsec

1996 ◽  
Vol 169 ◽  
pp. 231-240 ◽  
Author(s):  
Dan Gezari ◽  
Eli Dwek ◽  
Frank Varosi
Keyword(s):  
Galactic Center ◽  
Dust Emission ◽  
Infrared Emission ◽  
Mid Infrared ◽  
New Model ◽  
Central Engine ◽  
Direct Indication ◽  
Sgr A ◽  
Central Parsec ◽  
Array Camera

We have modeled the mid-infrared emission from the Galactic Center using our array camera images at eight wavelengths. The results suggest that the high infrared luminosity of the region is provided by a cluster of luminous stars. There is no direct indication in the new model results of a very luminous object or “central engine” near Sgr A∗.

scholarly journals Mid-Infrared Observations of the Galactic Center Arc and the Sgr A East HII Region

1989 ◽  
Vol 136 ◽  
pp. 287-292 ◽  
Author(s):  
F. Yusef-Zadeh ◽  
C. M. Telesco ◽  
R. Decher
Keyword(s):  
Galactic Center ◽  
Hii Regions ◽  
Radio Continuum ◽  
Radio Flux ◽  
Ir Camera ◽  
Hii Region ◽  
Sgr A ◽  
5 Ghz ◽  
Almost All ◽  
Ir Emission

We have used the 20-pixel IR camera to observe thermal IR emission from dust associated with the radio continuum Arc near the Galactic center and the cluster of HII regions in the immediate vicinity of Sgr A East. We detected strong 10μm emission from the eastern and western arched filaments (G0.1+0.08), from an unusual pistol-shaped structure known as G0.15–0.05 and from the brightest member of the Sgr A East HII region. Spatial maps of these features at 10μm with a resolution of 4.1″ × 4.2″ are presented and are compared with 5-GHz radio images. We find a general spatial correlation between the ionized gas and the dust distributions. The ratio of IR to radio flux densities is significantly different in the eastern and western arched filaments, which suggests that the source of heating has a softer spectrum along the eastern arched filaments. In addition, the ratio of IR to radio flux densities, which is typically ~10 in normal Galactic HII regions excited by O stars, is at least a factor of two higher than this value in almost all the sources we have observed. This suggests that additional mechanisms other than trapped Lymanαradiation should be present in heating the dust, e.g. stochastic heating of small dust grains by energetic particles associated with the nonthermal filaments.

scholarly journals Unusually Wide, High-Velocity Radio Recombination Lines from G0.15–0.05 in the Radio Arc

1989 ◽  
Vol 136 ◽  
pp. 275-280 ◽  
Author(s):  
F. Yusef-Zadeh ◽  
Mark Morris ◽  
J. H. van Gorkom
Keyword(s):  
Radial Velocity ◽  
Galactic Center ◽  
Galactic Plane ◽  
Line Profiles ◽  
Recombination Line ◽  
Ionized Gas ◽  
Hii Region ◽  
Sgr A ◽  
Relativistic Particles ◽  
Kinematic Properties

The H92αrecombination line was observed at 8 GHz toward the “pistol-shaped” HII region G0.15–0.05 using the VLA2in its most compact configuration. The line profiles of individual components of this source peak at VLSR=123 km/s and have total line widths of ~90 km/s. The kinematical structure of the “pistol” is unusual in that much of the neutral and ionized gas in this region is seen predominantly at either +50 or +20 km/s. The line width and radial velocity are the largest found in the Galactic center region with the exception of Sgr A West. We also found gas at VLSR=140 km/s associated with G0.18–0.04: the sickle-shaped feature which surrounds G0.15–0.05. The kinematic properties of G0.18–0.04 and G0.15–0.05 suggest that these two features are components of a single, but complex thermal system interacting with the nonthermal filaments of the radio Arc. In this regard, the width of the broad recombination line from G0.15–0.05, and its large radial velocity, might be explained as the interaction of streaming relativistic particles in the nonthermal filaments of the Arc impacting upon ambient gas clouds lying in the Galactic plane.

scholarly journals Modeling the orbital motion of Sgr A*’s near-infrared flares

2020 ◽  
Vol 635 ◽  
pp. A143 ◽  
Author(s):  
◽  
M. Bauböck ◽  
J. Dexter ◽  
R. Abuter ◽  
A. Amorim ◽  
...  
Keyword(s):  
Black Hole ◽  
Event Horizon ◽  
Near Infrared ◽  
Galactic Center ◽  
Orbital Motion ◽  
Plane Motion ◽  
Infrared Observations ◽  
Out Of Plane ◽  
Sgr A ◽  
Astrometric Data

Infrared observations of Sgr A* probe the region close to the event horizon of the black hole at the Galactic center. These observations can constrain the properties of low-luminosity accretion as well as that of the black hole itself. The GRAVITY instrument at the ESO VLTI has recently detected continuous circular relativistic motion during infrared flares which has been interpreted as orbital motion near the event horizon. Here we analyze the astrometric data from these flares, taking into account the effects of out-of-plane motion and orbital shear of material near the event horizon of the black hole. We have developed a new code to predict astrometric motion and flux variability from compact emission regions following particle orbits. Our code combines semi-analytic calculations of timelike geodesics that allow for out-of-plane or elliptical motions with ray tracing of photon trajectories to compute time-dependent images and light curves. We apply our code to the three flares observed with GRAVITY in 2018. We show that all flares are consistent with a hotspot orbiting at R ∼ 9 gravitational radii with an inclination of i ∼ 140°. The emitting region must be compact and less than ∼5 gravitational radii in diameter. We place a further limit on the out-of-plane motion during the flare.

scholarly journals Infrared observations of the nuclear region

1979 ◽  
Vol 84 ◽  
pp. 367-375 ◽  
Author(s):  
E. R. Wollman
Keyword(s):  
Power Output ◽  
Galactic Center ◽  
Far Infrared ◽  
Total Power ◽  
Nuclear Region ◽  
Infrared Observations ◽  
The Core ◽  
Sgr A ◽  
Central Parsec ◽  
Total Power Output

Infrared observations have provided considerable information about the structure and energetics of the galactic center. The stellar bulge dominates the mass and luminosity of the nuclear region. The luminosity of the bulge is strongly peaked toward the center, even within the central parsec. Dust in the nuclear disk absorbs the power output of the central portion of the bulge and reemits it in the far infrared. Near the center, molecular clouds move in a plane apparently tilted toward the Sun. Within the central few parsecs, or core, the inclination may be as large as 45°. The total power output of the core is about twice that of the bulge population alone. The source of excess luminosity is uncertain, but evidence points to ongoing star formation associated with the Sgr A molecular complex.

scholarly journals Class I methanol masers in the Galactic center

2013 ◽  
Vol 9 (S303) ◽  
pp. 147-149
Author(s):  
L. O. Sjouwerman ◽  
Y. M. Pihlström
Keyword(s):  
Galactic Center ◽  
Class I ◽  
Large Array ◽  
Maser Emission ◽  
Very Large Array ◽  
Sagittarius A ◽  
Current Location ◽  
Theoretical Predictions ◽  
Methanol Masers ◽  
Sgr A

AbstractWe report on the detection of 36 and 44 GHz Class I methanol (CH3OH) maser emission in the Sagittarius A (Sgr A) complex with the Karl G. Jansky Very Large Array (VLA). These VLA observations show that the Sgr A complex harbors at least three different maser tracers of shocked regions in the radio regime. The 44 GHz masers correlate with the positions and velocities of previously detected 36 GHz CH3OH masers, but less with 1720 MHz OH masers. Our detections agree with theoretical predictions that the densities and temperatures conducive for 1720 MHz OH masers may also produce 36 and 44 GHz CH3OH maser emission. However, many 44 GHz masers do not overlap with 36 GHz methanol masers, suggesting that 44 GHz masers also arise in regions too hot and too dense for 36 GHz masers to form. This agrees with the non-detection of 1720 MHz OH masers in the same area, which are thought to be excited under even cooler and less dense conditions. We speculate that the geometry of the 36 GHz masers outlines the current location of a shock front.

Cycles of Variability in Jupiter's Atmosphere from Ground-Based Mid-Infrared Observations

2021 ◽  
Author(s):  
Arrate Antunano ◽  
Leigh N Fletcher ◽  
Glenn S Orton ◽  
Henrik Melin ◽  
Padraig T. Donnelly ◽  
...  
Keyword(s):  
Mid Infrared ◽  
Infrared Observations

scholarly journals 3D moving mesh simulations of Galactic center cloud G2

2013 ◽  
Vol 9 (S303) ◽  
pp. 318-319 ◽  
Author(s):  
P. C. Fragile ◽  
P. Anninos ◽  
S. D. Murray
Keyword(s):  
Feeding Rate ◽  
Galactic Center ◽  
Equations Of State ◽  
Accretion Rate ◽  
Three Dimensional ◽  
Light Curves ◽  
Moving Mesh ◽  
Future Evolution ◽  
Sgr A ◽  
Gas Cloud

AbstractUsing three-dimensional, moving-mesh simulations, we investigate the future evolution of the recently discovered gas cloud G2 traveling through the galactic center. From our simulations we expect an average feeding rate onto Sgr A* in the range of (5−19) × 10−8M⊙ yr−1 beginning in 2014. This accretion varies by less than a factor of three on timescales ∼ 1 month, and shows no more than a factor of 10 difference between the maximum and minimum observed rates within any given model. These rates are comparable to the current estimated accretion rate in the immediate vicinity of Sgr A*, although they represent only a small (< 10%) increase over the current expected feeding rate at the effective inner boundary of our simulations (racc = 750 RS ∼ 1015 cm). We also explore multiple possible equations of state to describe the gas. In examining the Br-γ light curves produced from our simulations, we find that all of our isothermal models predict significant (factor of 10) enhancements in the luminosity of G2 as it approaches pericenter, in conflict with observations. Models that instead allow the cloud to heat as it is compressed do better at matching observations.

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