Tightly Correlated X-ray/H$\alpha$ Emitting Filaments in the Superbubble and Large-Scale Superwind of NGC 3079 (original) (raw)
Related papers
The Astrophysical Journal, 2002
Using Chandra and HST we show that X-ray and Hα filaments that form the 1.3-kpc diameter superbubble of NGC 3079 have strikingly similar patterns at ∼0. ′′ 8 resolution. This tight optical line/X-ray match seems to arise from cool disk gas that has been driven by the wind, with X-rays being emitted from upstream, stand-off bowshocks or by conductive cooling at the cloud/wind interfaces. We find that the soft X-ray plasma has thermal and kinetic energies E TH ∼ 2 × 10 56 η 0.5
The Collimated Wind in NGC 253
The Astrophysical Journal, 2003
Near-infrared Fabry-Perot imaging has revealed H 2 emission extended to about 130 pc from the disk of NGC 253. It is closely related to the hot plasma observed in soft X-rays: filamentary H 2 features are found at the edges of the hot plasma. These are the places of direct interaction between a superwind and its surrounding molecular gas. We suggest that the filamentary features actually trace a more or less conical shell-like structure, whose tangential line of sight to us is intensely observed. The H 2 emission shell is most likely from the molecular gas blown out or swept to the side by the hot plasma outflow. Dust is associated with this molecular gas structure. The outflow is tilted with respect to the disk, possibly suggesting the inhomogeneous nature of the interstellar medium in which the starburst takes place.
A 60 kpc Galactic Wind Cone in NGC 3079
The Astrophysical Journal
Galactic winds are associated with intense star formation and AGNs. Depending on their formation mechanism and velocity they may remove a significant fraction of gas from their host galaxies, thus suppressing star formation, enriching the intergalactic medium, and shaping the circumgalactic gas. However, the long-term evolution of these winds remains mostly unknown. We report the detection of a wind from NGC 3079 to at least 60 kpc from the galaxy. We detect the wind in FUV line emission to 60 kpc (as inferred from the broad FUV filter in GALEX) and in X-rays to at least 30 kpc. The morphology, luminosities, temperatures, and densities indicate that the emission comes from shocked material, and the O/Fe ratio implies that the X-ray emitting gas is enriched by Type II supernovae. If so, the speed inferred from simple shock models is about 500 km s −1 , which is sufficient to escape the galaxy. However, the inferred kinetic energy in the wind from visible components is substantially smaller than canonical hot superwind models.
The Astronomical Journal, 2000
Arcsecond-resolution X-ray imaging of the nucleus of the nearby starburst galaxy NGC 253 with Chandra reveals a well-collimated, strongly limb-brightened, kiloparsec-scale conical outflow from the central starburst region. The outflow is very similar in morphology to the known Hα outflow cone, on scales down to 20 pc. This provides, for the first time, robust evidence that both X-ray and Hα emission come from low volume filling factor regions of interaction between the fast energetic wind of SN-ejecta and the denser ambient interstellar medium (ISM), and not from the wind fluid itself. We provide estimates of the (observationally and theoretically important) filling factor of the X-ray emitting gas, of between ∼ 4 and 40 per cent, consistent with an upper limit of ∼ 40 per cent based directly on the observed limb-brightened morphology of the outflow. Only 20 per cent of the observed X-ray emission can come from the volume-filling, metal-enriched, wind fluid itself. Spatially-resolved spectroscopy of the soft diffuse thermal X-ray emission reveals that the predominant source of spectral variation along the outflow cones is due to strong variation in the absorption, on scales of ∼ 60 pc, there being little change in the characteristic temperature of the emission. We show that these observations are easily explained by, and fully consistent with, the standard model of a superwind driven by a starburst of NGC 253's observed power. If these results are typical of all starburst-driven winds, then we do not directly see all the energy and gas (in particular the hot metal-enriched gas) transported out of galaxies by superwinds, even in X-ray emission.
Jet‐ and Wind‐driven Ionized Outflows in the Superbubble and Star‐forming Disk of NGC 3079
The Astrophysical Journal, 2001
HST WFPC2 images are presented that span the inner ∼19 kpc diameter of the edge-on galaxy NGC 3079; they are combined with optical, emission-line imaging spectrophotometry and VLA images of radio polarization vectors and rotation measures. Ionized gas filaments within 9-kpc diameter project up to 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 streams with large velocities and velocity dispersions (FWHM ≈450 km s −1 ). The brightest stream emits ≈ 10% of the superbubble Hα flux and extends for 250 pc along the axis of the VLBI radio jet to one corner of the base of the superbubble. The other four streams are not connected to the jet, instead curving up to the vertical ≈ 0.6 kpc above the galaxy disk, then dispersing as a spray of droplets each with ≈ 10 3 √ f M of ionized gas (the volume filling factor f > 3 × 10 −3 ). Shredded clumps of disk gas form a similar structure in hydrodynamical models of a galaxy-scale wind. The pattern of magnetic fields and the gaseous kinematics also suggest that a wind of mechanical luminosity L w ≈ 10 43 ergs s −1 has stagnated in the galaxy disk at a radius of ∼ 800 pc, has flared to larger radii with increasing height as the balancing ISM pressure reduces above the disk, and has entrained dense clouds into a "mushroom vortex" above the disk. Hα emissivity of the filaments limits densities to n e > 4.3 f −1/2 cm −3 , hence kinetic energy and momentum to (0.4 − 5) × 10 55 √ f ergs and (1.6 − 6) × 10 47 √ f dyne s, respectively; the ranges result from uncertain space velocities. A prominent star-forming complex elsewhere in the galaxy shows a striking spray of linear filaments that extend for hundreds of parsecs to end in unresolved "bullets."
From ultraluminous X-ray sources to ultraluminous supersoft sources: NGC 55 ULX, the missing link
Monthly Notices of the Royal Astronomical Society
In recent work with high-resolution reflection grating spectrometers (RGS) aboard XMM-Newton, Pinto et al. have discovered that two bright and archetypal ultraluminous X-ray sources (ULXs) have strong relativistic winds in agreement with theoretical predictions of high accretion rates. It has been proposed that such winds can become optically thick enough to block and reprocess the disc X-ray photons almost entirely, making the source appear as a soft thermal emitter or ultraluminous supersoft X-ray source (ULS). To test this hypothesis, we have studied a ULX where the wind is strong enough to cause significant absorption of the hard X-ray continuum: NGC 55 ULX. The RGS spectrum of NGC 55 ULX shows a wealth of emission and absorption lines blueshifted by significant fractions of the light speed (0.01-0.20)c indicating the presence of a powerful wind. The wind has a complex dynamical structure with the ionization state increasing with the outflow velocity, which may indicate launching from different regions of the accretion disc. The comparison with other ULXs such as NGC 1313 X-1 and NGC 5408 X-1 suggests that NGC 55 ULX is being observed at higher inclination. The wind partly absorbs the source flux above 1 keV, generating a spectral drop similar to that observed in ULSs. The softening of the spectrum at lower (∼ Eddington) luminosities and the detection of a soft lag agree with the scenario of wind clumps crossing the line of sight, partly absorbing and reprocessing the hard X-rays from the innermost region.
The Astrophysical Journal, 2002
We present a detailed case study of the diffuse X-ray and Hα emission in the halo of NGC 253, a nearby edge-on starburst galaxy driving a galactic superwind. The arcsecond spatial resolution of the ACIS imaging spectroscope on the Chandra X-ray Observatory allows us to study the spatial and spectral properties of the diffuse X-ray emitting plasma, at a height of between 3 and 9 kpc above the disk in the northern halo of NGC 253, with greatly superior spatial and spectral resolution compared to previous X-ray instruments. We find statistically significant structure within the diffuse emission on angular scales down to ∼ 10 ′′ (∼ 130 pc), and place limits on the luminosity of any X-ray-emitting "clouds" on smaller scales. There is no statistically significant evidence for any spatial variation in the spectral properties of the diffuse emission over scales from several ∼ 400 pc to ∼ 3 kpc. The spectrum of the diffuse X-ray emission is clearly thermal, although with the higher spectral resolution and sensitivity of Chandra it is clear that current simple spectral models do not provide a physically meaningful description of the spectrum. In particular, the fitted metal abundances are unphysically low. There is no convincing evidence for diffuse X-ray emission at energies above 2 keV in the halo. We show that the X-shaped soft X-ray morphology of the superwind previously revealed by ROSAT is matched by very similar X-shaped Hα emission, extending at least 8 kpc above the plane of the galaxy. In the northern halo the X-ray emission appears to lie slightly interior to the boundary marked by the Hα emission. The total 0.3-2.0 keV energy band X-ray luminosity of the northern halo L X ∼ 5 × 10 38 erg s −1 , is very similar to the halo Hα luminosity of L Hα ∼ 4 × 10 38 erg s −1 , both of which are a small fraction of the estimated wind energy injection rate of ∼ 10 42 erg s −1 from supernovae in the starburst. We show that there are a variety of models that can simultaneously explain spatially-correlated X-ray and Hα emission in the halos of starburst galaxies, although the physical origin of the various emission components can be very different in different models. These findings indicate that the physical origin of the X-ray-emitting milliondegree plasma in superwinds is closely linked to the presence of much cooler and denser T ∼ 10 4 gas, not only within the central kpc regions of starbursts, but also on ∼ 10 kpc-scales within the halos of these galaxies.
The Astrophysical Journal, 2009
We present direct evidence for dense clumps of matter in the companion wind in a Supergiant Fast X-ray Transient (SFXT) binary. This is seen as a brief period of enhanced absorption during one of the bright, fast flares that distinguish these systems. The object under study was IGR J17544-2619, and a total of 236 ks of data were accumulated with the Japanese satellite Suzaku. The activity in this period spans a dynamic range of almost 10 4 in luminosity and gives a detailed look at SFXT behavior.