We have investigated the structure, kinematics, and emission spectrum of the ionized gas in the synchrotron superbubble in the irregular galaxy IC 10 based on observations with the 6-m Special Astrophysical Observatory telescope with the SCORPIO focal reducer in three modes: direct imaging in the [SII](6717+6731)A lines, long-slit spectroscopy, and spectroscopy with a scanning Fabry--Perot interferometer. We have identified a bright (in the [SII] lines) filamentary optical shell and determined its expansion velocity, mass, and kinetic energy. The nature of the object is discussed.
The nature of the synchrotron superbubble in the IC 10 galaxy is discussed using the results of our investigation of its ionized gas structure, kinematics, and emission spectrum from observations made with the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences, and based on our analysis of the radio emission of the region. The hypernova explosion is shown to be a more plausible mechanism of the formation of the synchrotron superbubble compared with the earlier proposed model of multiple supernova explosions. A compact remnant of this hypernova may be iden…
The Wisconsin H-Alpha Mapper (WHAM) Northern Sky Survey has revealed a loop of H II reaching 1300 pc from the Galactic midplane above the Cas OB6 association in the Perseus sprial arm. This enormous feature surrounds and extends far above the "W4 Chimney" identified by Normandeau et al. and appears to be associated with the star formation activity near the W3/W4/W5 H II region complex. The existence of this ionized structure suggests that past episodes of massive star formation have cleared the H I from an enormous volume above the Perseus arm, allowing Lyman continuum photons from O stars nea…
We present Halpha and [SII] observations for the Local Group irregular galaxy IC 1613 using the PUMA scanning Fabry-Perot interferometer. Our goal is to analyze the kinematics of the ionized gas in the complex sample of superbubbles located in the whole extension of our field (10 arcmin), which includes most of the optical emission of this galaxy, and to study the inter-relationship between young stellar associations and nebulae based on a previous study that we have made on the stellar associations of the central region of this galaxy. The ionized gas in this galaxy is distributed in classica…
We have combined measurements of the kinematics, morphology, and oxygen abundance of the ionized gas in \IZw18, one of the most metal-poor galaxies known, to examine the star formation history and chemical mixing processes.
HST WFPC2 images are presented that span the inner 19 kpc diameter of the edge-on spiral galaxy NGC 3079; they are combined with ground-based Halpha+[N II] Fabry-Perot spectra and VLA images of radio polarization vectors and rotation measures. Ionized gas filaments within 9 kpc diameter project ~3 kpc above the disk, with the brightest forming the 1 kpc diameter superbubble. They are often resolved into strands ~0."3 (25 pc) wide which emerge from the nuclear CO ring as five distinct gas streams with velocity gradients and dispersions of hundreds of km/s. One stream flows for 250 pc and aligns…
We have obtained high-resolution HI observations of N44, one of the largest HII complexes in the Large Magellanic Cloud. The distribution and internal motions of the HI gas show dynamic effects of fast stellar winds and supernova blasts. Numerous HI holes are detected, with the most prominent two corresponding to the optically identified superbubbles Shell 1 and Shell 2. The HI gas associated with Shell 1 shows an expansion pattern similar to that of the ionized gas shell, but the mass and kinetic energy of the HI shell are 3--7 times those of the ionized gas shell. The total kinetic energy of…
We report on observations of several optical emission lines toward a variety of newly revealed faint, large-scale Halpha-emitting regions in the Galaxy. The lines include [NII] 6583, [NII] 5755, [SII] 6716, [OIII] 5007, and HeI 5876 obtained with the Wisconsin H-Alpha Mapper (WHAM) toward sightlines that probe superbubbles, high latitude filamentary features, and the more diffuse warm ionized medium (WIM). Our observations include maps covering thousands of square degrees toward the well-known Orion-Eridanus bubble, a recently discovered 60deg x 20deg bipolar superbubble centered in Perseus, p…
We present high spatial resolution (2.3"x1.9" or 43 pc x 36 pc at D = 3.9 Mpc) 100 GHz millimeter-wave continuum emission observations with the Nobeyama Millimeter Array toward an expanding molecular superbubble in the central region of M82. The 100 GHz continuum image, which is dominated by free-free emission, revealed that the four strongest peaks are concentrated at the inner edge of the superbubble along the galactic disk. The production rates of Lyman continuum photons calculated from 100 GHz continuum flux at these peaks are an order of magnitude higher than those from the most massive s…
We present evidence for an expanding superbubble in M82 (diameter: ~130 pc, expansion velocity: ~45 km/s, mass: ~8*10^6 SM). It is seen in the 12CO(J=1-0), 12CO(J=2-1), 13CO(J=1-0) and C18O(J=1-0) lines. The superbubble is centred around the most powerful supernova remnant in M82, 41.9+58. The CO observations show that the molecular superbubble already broke out of the disk. This scenario is supported by ROSAT HRI observations which suggest that hot coronal gas originating from inside the shell is the main contributor to the diffuse X-ray outflow in M82. We briefly discuss observations of the …
N51D (= DEM L 192) appears at first glance as a nearly circular, 120pc diameter bubble of ionized gas around the LMC OB association LH 54. A deeper look reveals a complex web of filaments and deviations from radial expansion. Using a deep XMM-Newton X-ray pointing centered on N51D we find that diffuse soft X-ray emitting gas fills the whole superbubble as delineated by the H-alpha filaments. Contrary to recent findings for galactic winds, the correlation between H-alpha and X-ray surface brightness is not good. The X-ray spectrum of this diffuse gas cannot be fitted with the LMC abundance patt…
New observations at high latitudes above the HII region W4 show that the structure formerly identified as a chimney candidate, an opening to the Galactic halo, is instead a superbubble in the process of fragmenting and possibly evolving into a chimney. Data at high Galactic latitudes (b > 5 degrees) above the W3/W4 star forming region at 1420 and 408 MHz Stokes I (total power) and 1420 MHz Stokes Q and U (linear polarization) reveal an egg-shaped structure with morphological correlations between our data and the H-alpha data of Dennison, Topasna, & Simonetti. Polarized intensity images show de…
We present an X-ray tour of diffuse emission in the 30 Doradus star-forming complex in the Large Magellanic Cloud using high-spatial-resolution X-ray images and spatially-resolved spectra obtained with the Advanced CCD Imaging Spectrometer aboard the Chandra X-ray Observatory. The dominant X-ray feature of the 30 Doradus nebula is the intricate network of diffuse emission generated by interacting stellar winds and supernovae working together to create vast superbubbles filled with hot plasma. We construct maps of the region showing variations in plasma temperature (T = 3--9 million degrees), a…
We present Chandra ACIS observations of N157B, a young supernova remnant located in the 30 Doradus star-formation region of the LMC. This remnant contains the most energetic pulsar known (PSR J0537-6910), which is surrounded by a bright nonthermal nebula that likely represents a toroidal pulsar wind terminal shock observed edge-on. We confirm the non-thermal nature of the comet-shaped X-ray emission feature and show that the spectral steepening of this feature away from the pulsar is quantitatively consistent with synchrotron cooling of shocked pulsar wind particles flowing downstream at a bul…
LMC2 has the highest X-ray surface brightness of all know supergiant shells in the Large Magellanic Cloud (LMC). The X-ray emission peaks within the ionized filaments that define the shell boundary, but also extends beyond the southern border of LMC2 as an X-ray bright spur. ROSAT HRI images reveal the X-ray emission from LMC2 and the spur to be truly diffuse, indicating a hot plasma origin. We have obtained ROSAT PSPC and ASCA SIS spectra to study the physical conditions of the hot gas interior to LMC2 and the spur. Raymond-Smith thermal plasma model fits to the X-ray spectra, constrained by …
We present R-band and H-alpha+[N II] narrow-band imaging of FCC032, FCC206 and FCCB729, three dwarf elliptical galaxies (dEs) in the Fornax Cluster. These dEs contain significant amounts of ionized gas. FCC032 harbours a large ionized gas complex, consisting of several individual clouds, a superbubble and a filament that extends away from the galaxy centre. The ionized gas structures observed in FCC032 bear a strong resemblance to those observed in more gas-rich and more fiercely star-forming dwarf galaxies. FCC206, a very low surface brightness dE, contains one faint extended emission region,…
We investigated the kinematics of ionized gas in an extended (20 degrees by 15 degrees) region containing the X-ray Superbubble in Cygnus with the aim of finding the shell swept up by a strong wind from Cyg OB2. H-alpha observations were carried out with high angular and spectral resolutions using a Fabry-Perot interferometer attached to the 125-cm telescope at the Crimean Observatory of the Sternberg Astronomical Institute. We detected high-velocity gas motions, which could result from the expansion of the hypothetical shell at a velocity of 25-50 km/s. Given the number of OB stars increased …
We present new H alpha and [O III] 5007 narrow band images of the starbursting dwarf galaxy NGC 4214, obtained with the WFPC2 onboard HST, together with VLA observations of the same galaxy. The HST images resolve features down to physical scales of 2-5 pc, revealing several young (<10 Myr) star forming complexes of various ionized gas morphologies (compact knots, complete or fragmentary shells) and sizes (10-200 pc). Our results are consistent with a uniform set of evolutionary trends: The youngest, smaller, filled regions that presumably are those just emerging from dense star forming clouds,…
We present an analysis of the thin layer of Galactic warm ionized gas at an angular resolution ~ 10'. This is carried out using radio continuum data at 1.4 GHz, 2.7 GHz and 5 GHz in the coordinate region 20 < l < 30 deg, -1.5 < b < +1.5 deg. For this purpose, we evaluate the zero level of the 2.7 and 5 GHz surveys using auxiliary data at 2.3 GHz and 408 MHz. The derived zero level corrections are T_{zero}(2.7 GHz)=0.15 +/- 0.06 K and T_{zero}(5 GHz)=0.1 +/- 0.05 K. We separate the thermal (free-free) and non-thermal (synchrotron) component by means of a spectral analysis performed adopting an …
We present in this paper a detailed study of the kinematical properties of the ionized gas around the young massive star clusters in the nucleus of NGC 4214. The analysis is based on bidimensional spectroscopical data, allowing to derive the spatial variation of different properties (intensity, velocity and width / line splitting) of the emission lines Hαand [O III] λ5007 along the nuclear region. We have found that the Giant H II region around the two most massive clusters in NGC 4214 (A and B) is resolved into two clearly separated regions. We have not detected superbubbles with the properti…
A joint action of depth and bandwidth depolarization in the interstellar medium is considered using a model of N homogeneous synchrotron layers with Faraday rotation. The bandwidth depolarization can be used in multifrequency polarimetric observations of Galactic diffuse synchrotron radio emission to investigate the interstellar ionized medium and magnetic field in the direction to the Faraday-thick objects of known distances.
VLA HI observations of the dwarf irregular galaxy NGC 2188 show that the gas and stars have spatial distributions which are substantially different. One end of the optical disk is strongly gas deficient, while neutral gas extends into the halo over distances of more than 2 kpc from the midplane. This and the peculiar velocity field suggest that NGC 2188 is a perturbed system, although it is not obviously an interacting galaxy. In addition, NGC 2188 is remarkable for its interstellar disk-halo connection. An Halpha image of NGC 2188 shows the presence of spectacular features of ionized gas exte…
The standard model for radio supernovae considers that the observed synchrotron radio emission arises from the high-energy shell that results from the strong interaction between the expanding supernova ejecta and the circumstellar medium. This emission is considered to be only partially absorbed by ionized thermal electrons in the circumstellar wind of the progenitor star. Based on a study of the radio light curves of the type II supernova SN1993J, we present evidence of synchrotron self-absorption. Our modeling of the radio light curves requires a large initial magnetic field, of about 30 Gau…
We have observed the young Galactic supernova remnant Kes 75 with the Chandra X-ray Observatory. This object is one of an increasing number of examples of a shell-type remnant with a central extended radio core harboring a pulsar. Here we present a preliminary spatially resolved spectroscopic analysis of the Kes~75 system. We find that the spectrum of the pulsar is significantly harder than that of the wind nebula, and both of these components can be isolated from the diffuse thermal emission that seems to follow the same distribution as the extended radio shell. When we characterize the therm…
We have used polarimetric imaging to study the magneto-ionic medium of the Galaxy, obtaining 1420 MHz images with an angular resolution of 1' over more than 40 square-degrees of sky around the W3/W4/W5/HB3 HII region/SNR complex in the Perseus Arm. Features detected in polarization angle are imposed on the linearly polarized Galactic synchrotron background emission by Faraday rotation arising in foreground ionized gas having an emission measure as low as 1 cm^{-6} pc. Several new remarkable phenomena have been identified, including: mottled polarization arising from random fluctuations in a ma…
Radio astronomy has provided evidence for the presence of ionized atmospheres around almost all classes of non-degenerate stars. Magnetically confined coronae dominate in the cool half of the Hertzsprung-Russell diagram. Their radio emission is predominantly of non-thermal origin and has been identified as gyrosynchrotron radiation from mildly relativistic electrons, apart from some coherent emission mechanisms. Ionized winds are found in hot stars and in red giants. They are detected through their thermal, optically thick radiation, but synchrotron emission has been found in many systems as w…
Full sky maps are made in five microwave frequency bands to separate the temperature anisotropy of the CMB from foreground emission. We define masks that excise regions of high foreground emission. The effectiveness of template fits to remove foreground emission from the WMAP data is examined. These efforts result in a CMB map with minimal contamination and a demonstration that the WMAP CMB power spectrum is insensitive to residual foreground emission. We construct a model of the Galactic emission components. We find that the Milky Way resembles other normal spiral galaxies between 408 MHz and…
We have used the VLBA to produce a high dynamic range image of the nucleus of NGC 6251 at 1.6 GHz and snapshot images at 5.0, 8.4, and 15.3 GHz to search for emission from a parsec-scale counterjet. Previous VLBI images at 1.6 GHz have set a lower limit for the jet/counterjet brightness ratio near the core at about 80:1, which is larger than expected given the evidence that the radio axis is fairly close to the plane of the sky. A possible explanation is that the inner few pc of the counterjet is hidden by free-free absorption by ionized gas associated with an accretion disk or torus. This wou…
In this paper, we explore the possibility that the radiative properties of the most compact region in NGC 6251* may be understood in the same sense as Sgr A*, though with some telling differences that may hint at the nature of jet formation. We show that observations of this object with ASCA, ROSAT, HST and VLBI together may be hinting at a picture in which Bondi-Hoyle accretion from an ambient ionized medium feeds a standard disk accreting at ~ 4.0*10^{22} g s^{-1}. Somewhere near the event horizon, this plasma is heated to >10^{11} K, where it radiates via thermal synchrotron (producing a ra…
We study the spectral and morphological characteristics of the diffuse Galactic emission in the WMAP temperature data using a template-based multi-linear regression, and obtain the following results. 1. We confirm previous observations of a bump in the dust-correlated spectrum, consistent with the Draine & Lazarian spinning dust model. 2. We also confirm the "haze" signal in the inner Galaxy, and argue that it does not follow a free-free spectrum as first thought, but instead is synchrotron emission from a hard electron cosmic-ray population. 3. In a departure from previous work, we allow the …
We present new multi-frequency radio continuum imaging of the dwarf starburst galaxy NGC 625 obtained with the Very Large Array. Data at 20, 6, and 3.6 cm reveal global continuum emission dominated by free-free emission, with only mild synchrotron components. Each of the major HII regions is detected; the individual spectral indices are thermal for the youngest regions (showing strongest H Alpha emission) and nonthermal for the oldest. We do not detect any sources that appear to be associated with deeply embedded, dense, young clusters, though we have discovered one low-luminosity, obscured so…
We present results from a BeppoSAX (July 2001) observation of the FRI radio galaxy NGC6251, together with a re-analysis of archival ASCA (October 1994) and Chandra (September 2000) data. The weak detection above 10 keV and the lack of iron fluorescent K-alpha emission lines in the BeppoSAX spectrum rule out that the bulk of the X-ray emission is due to an obscured Seyfert nucleus. The study of the multiwavelength spectral energy distribution suggests instead that X-rays probably originate as inverse-Compton of synchrotron seed photons in a relativistic jet, indicating that NGC6251 hosts a low …
We have combined infrared data with HI, H2 and HII surveys in order to spatially decompose the observed dust emission into components associated with different phases of the gas. An inversion technique is applied. For the decomposition, we use the IRAS 60 and 100 micron bands, the DIRBE 140 and 240 micron bands, as well as Archeops 850 and 2096 micron wavelengths. In addition, we apply the decomposition to all five WMAP bands. We obtain longitude and latitude profiles for each wavelength and for each gas component in carefully selected Galactic radius bins.We also derive emissivity coefficient…
In this paper we present a broad-band study of the X-ray emission of the blazar PKS1830-211 based on Chandra and Integral observations. Notwithstanding the high redshift (z=2.507), it is a bright X-ray source (F(2-10 keV)~10^{-11} erg cm^{-2} s^{-1}), due to gravitational lensing by an intervening galaxy at z=0.89. Previous X-ray observations attribute the observed absorption at E<2 keV to the lensing galaxy. Our analysis, although not in contrast with this hypothesis, suggests also the possibility of an intrinsic (ionized) absorption, taking place at the front side of the jet. This scenario i…
