A5016344628- Astrophysics and Star Formation Studies
- Astrophysical Phenomena and Observations
- Astrophysics and Cosmic Phenomena
- Stellar, planetary, and galactic studies
- Pulsars and Gravitational Waves Research
- Gamma-ray bursts and supernovae
- Astronomy and Astrophysical Research
- Solar and Space Plasma Dynamics
- Astro and Planetary Science
- Astronomical Observations and Instrumentation
- Galaxies: Formation, Evolution, Phenomena
- Radio Astronomy Observations and Technology
- High-pressure geophysics and materials
- Atomic and Molecular Physics
- Molecular Spectroscopy and Structure
- Mechanics and Biomechanics Studies
- Magnetic confinement fusion research
- Atmospheric Ozone and Climate
- Ionosphere and magnetosphere dynamics
- Particle accelerators and beam dynamics
- Geophysics and Gravity Measurements
- Dark Matter and Cosmic Phenomena
- Adaptive optics and wavefront sensing
- Particle Accelerators and Free-Electron Lasers
- Laser-induced spectroscopy and plasma
Northwestern University
2015-2024
Max Planck Society
2015
Max Planck Institute for Radio Astronomy
2015
University of Hawaii System
2010
Evanston Hospital
2005
Instituto de Estructura de la Materia
1998
Consejo Superior de Investigaciones Científicas
1998
Institut d'Astrophysique Spatiale
1998
Université Paris-Saclay
1998
Université Grenoble Alpes
1998
We derive the extinction curve towards Galactic Center from 1 to 19 micron. use hydrogen emission lines of minispiral observed by ISO-SWS and SINFONI. The free flux reference is 2 cm continuum VLA. Towards inner 14" * 20" we find an A(2.166 micron)=2.62 +/- 0.11, with a power-law slope alpha=-2.11 0.06 shortward 2.8 micron, consistent average near infrared recent literature. At longer wavelengths, however, that grayer than it not possible fit dust model consisting pure carbonaceous silicate...
Abstract The inner ∼200 pc region of the Galaxy contains a 4 million M ⊙ supermassive black hole (SMBH), significant quantities molecular gas, and star formation cosmic-ray energy densities that are roughly two orders magnitude higher than corresponding levels in Galactic disk. At distance only 8.2 kpc, presents astronomers with unique opportunity to study diverse range energetic astrophysical phenomena, from stellar objects extreme environments, SMBH star-formation-driven feedback processes...
Abstract We present the first results of JWST Cycle 1 and 2 observations Sgr A* using NIRCam taken simultaneously at 2.1 4.8 μ m for a total ~48 hr over seven different epochs in 2023 2024. find correlated variability all epochs, continual short-timescale (a few seconds) variability, epoch-to-epoch variable emission implying long-term (~days to months) A*. A highlight this analysis is evidence subminute, horizon-scale time A*, probing inner accretion disk size scales. The power spectra light...
We report the discovery of an X-ray pulsar in young, massive Galactic star cluster Westerlund 1. detected a coherent signal from brightest source cluster, CXO J164710.2-455216, during two Chandra observations on 2005 May 22 and June 18. The period is 10.6107(1) s. place upper limit to derivative Pdot<2e-10 s/s, which implies that spin-down luminosity Edot<3e33 erg/s. L_X = 3(+10,-2)e33 (D/5 kpc)^2 erg/s, spectrum can be described by kT 0.61+/-0.02 keV blackbody with radius R_bb...
The central kpc of the Milky Way might be expected to differ significantly from rest Galaxy with regard gasdynamics and formation young stellar objects (YSOs). We probe this possibility mid-infrared observations obtained Infrared Array Camera Multiband Imaging Photometer on Spitzer Midcourse Space Experiment. use color–color diagrams spectral energy distribution (SED) fits explore nature YSO candidates (including 4.5 μm excesses possibly due molecular emission). There is an asymmetry in...
view Abstract Citations (195) References (113) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Structural Details of the Sagittarius A Complex: Evidence for a Large-Scale Poloidal Magnetic Field in Galactic Center Region Yusef-Zadeh, F. ; Morris, Mark Radio observations Sgr complex at both 6 and 20 cm indicate that diffuse radio structure surrounding East West consists two large-scale components. The first these is pc diameter halo which appears to be...
The high energy activity in the inner few degrees of Galactic center is traced by diffuse radio, X-ray and gamma-ray emission. physical relationship between different components gas emitting at multiple wavelengths a focus this work. We first present radio continuum observations using Green Bank Telescope model nonthermal spectrum terms broken power-law distribution GeV electrons synchrotron radiation. show that emission detected Fermi primarily due to bremsstrahlung produced population...
We present a sensitive $λ$20cm VLA continuum survey of the Galactic center region using new and archival data based on multi-configuration observations taken with relatively uniform {\it uv} coverage. The high dynamic range images cover regions within $-2^\circ < l 5^\circ$ $-40' b 40'$ spatial resolution $\approx30''$ 10$''$. wide field imaging technique is used to construct low-resolution mosaic 40 overlapping pointings. image includes Effelsburg filling low frequency data. also twenty...
We have carried out Very Large Array (VLA) continuum observations to study the variability of Sgr A* at 43 GHz (λ = 7 mm) and 22 13 mm). A low level flare activity has been detected with a duration ~2 hr these frequencies, showing peak emission leading by ~20-40 minutes. The overall characteristics are interpreted in terms plasmon model van der Laan considering ejection adiabatic expansion uniform, spherical plasma blob due activity. observed spectral index, ν-α, α 1.6 is consistent...
We present an observation with the Chandra X-ray Observatory of unusual radio source G359.23-0.82 ("the Mouse"), along updated timing data from Parkes telescope on coincident young pulsar J1747-2958. find that is a very luminous (L_X [0.5-8.0 keV] = 5e34 ergs/s for distance 5 kpc), whose morphology consists bright head PSR J1747-2958, plus 45"-long narrow tail power-law spectrum steepens pulsar. thus confirm bow-shock wind nebula powered by J1747-2958; nebular stand-off implies moving Mach...
view Abstract Citations (144) References (14) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Linear Filaments of the Radio Arc near Galactic Center Yusef-Zadeh, Farhad ; Morris, Mark High-resolution radio continuum VLA images a segment center arc centered at G0.16-0.15 wavelengths both 6 and 20 cm are presented. In this segment, highest multiplicity filaments, largest degree linear polarization, maximum rotation measure -5500 rad/sq m between 6.166 6.363...
Using a high-resolution radio-continuum image made at frequency of 4.8 GHz, the authors discuss radio source G0.18-0.04 located intersection galactic center Arc with plane. In this direction, is composed set linear, nonthermal filamentary structures superimposed on narrow, sickle-shaped, thermal feature which crosses them. The suggests physical interaction between and structures. argue that magnetic field dynamically important estimate its strength very large, ≡10<SUP>-3</SUP>G. Furthermore,...
We present a catalog of 9017 X-ray sources identified in Chandra observations 2°× 08 field around the Galactic center. This enlarges number known region by factor 2.5. The incorporates all ACIS-I as 2007 August, which total 2.25 Ms exposure. At distance to center (8 kpc), we are sensitive with luminosities 4 × 1032 erg s−1 (0.5–8.0 keV; 90% confidence) over an area 1 deg2, and up order magnitude more deepest exposure (1.0 Ms) Sgr A*. positions 60% our accurate <1 '' (95% confidence), 20%...
In this paper, we examine properties of the variable source Sgr A* in near-infrared (NIR) using a very extensive Ks-band data set from NACO/VLT observations taken 2004–2009. We investigate variability with two different photometric methods and analyze its flux distribution. find that is continuously emitting near-infrared, some occurring on timescales as long weeks. The distribution can be described by lognormal at low intrinsic fluxes (≲5 mJy, dereddened AKs = 2.5). has median ≈1.1 but...
Abstract The Survey of Water and Ammonia in the Galactic Center (SWAG) covers Central Molecular Zone (CMZ) Milky Way at frequencies between 21.2 25.4 GHz obtained Australia Telescope Compact Array ∼0.9 pc spatial ∼2.0 km s −1 spectral resolution. In this paper, we present data on inner ∼250 (1.°4) Sgr C B2. We focus hyperfine structure metastable ammonia inversion lines ( J , K ) = (1, 1)–(6, 6) to derive column density, kinematics, opacity, kinetic gas temperature. CMZ molecular clouds,...
We present radio images within 30'' of Sgr A* based on recent VLA observations at 34 GHz with 7.8 μJy sensitivity and resolution mas. report 44 partially resolved compact sources clustered in two regions the E arm ionized gas that orbits A*. These have size scales ranging between ∼50 200 mas (400–1600 AUs), a bow-shock appearance facing direction Unlike previously identified near-IR but associated massive stars, these do not appear to counterparts 3.8 μm. interpret as candidate population...
Abstract We present high-pass-filtered continuum images of the inner 3.°5 × 2.°5 Galactic center at 20 cm with 6.″4 resolution. These mosaic are taken MeerKAT and reveal a large number narrow filaments, roughly an order magnitude increase in their numbers compared to past measurements. For first time, we carry out population studies spectral index magnetic field entire region. The mean indices filaments steeper than supernova remnants (SNRs) (−0.62) value α ∼ −0.83. variation is much larger...
Radio observations of the Sgr A region have been carried out at 1720 MHz transition OH molecule, using Very Large Array and Australia Telescope Compact Array. OH(1720 MHz) maser emission is detected seven different positions within a few arcminutes Galactic center. Most masers are located to southeast A*, boundary East nonthermal source with M-0.02-0.07 molecular cloud. One circumnuclear disk (CND), another may arise as result an expansion into gas northwest A*. It likely that these features...
We report the discovery of a widespread population collisionally excited methanol J = 4_{-1} to 3$_0 E sources at 36.2 GHz from inner 66'x18' (160x43 pc) Galactic center. This spectral feature was imaged with resolution ~16.6 km/s taken 41 channels VLA continuum survey center region. The revelation 356 sources, most which are maser candidates, suggests large abundance in gas phase There is also spatial and kinematic correlation between SiO (2--1) CH3OH emission four clouds: +50 +20 clouds...
The Arches cluster is an extraordinarily compact massive star with a core radius of about 10'' (~0.4 pc) and consisting more than 150 O candidates initial stellar masses greater 20 M☉ near G0.12-0.02. X-ray observations the radio Arc Galactic center at l ~ 02, which contains cluster, have been carried out Advanced CCD Imaging Spectrometer (ACIS) on board Chandra X-Ray Observatory. We report detection two sources from embedded within bath diffuse emission extending beyond edge to least 90'' ×...