The Collimated Wind in NGC 253 (original) (raw)
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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
Superwind-Driven Intense H 2 Emission in NGC 6240
Publications of the Astronomical Society of Japan, 2000
We have performed a long-slit K band spectroscopic observation of the luminous infrared galaxy NGC 6240. Spatially extended H 2 emission is detected over 3.3 kpc around the two nuclei. The peak position of the H 2 v = 1 − 0 S(1) emission in the slit is located ∼ 0. ′′ 3 − 0. ′′ 4 north of the southern nucleus. It is almost the midpoint between the southern nucleus and the peak position of the 12 CO (J = 1 − 0) emission. Based on the line-ratio analyses, we suggest the excitation mechanism of H 2 is pure thermal at most positions. In the northern region including the northern nucleus, the H 2 velocity field shows only a slight velocity gradient and is not highly disturbed. On the other hand, the kinematics of the H 2 emitting gas is more complicated around the southern nucleus and its south region. In the southern region we find the following three velocity components in the H 2 emission: the blueshifted shell component (≈ −250 km s −1 with respect to V sys ) which is recognized as a distinct C-shape distortion in the velocity field around the southern nucleus, the high-velocity blueshifted "wing" component (∼ −1000 km s −1 with respect to V sys ), and the component indicating possible line splitting of ∼ 500 km s −1 . The latter two components are extended to the south from the southern nucleus. We show that the kinematic properties of these three components can be reproduced by expanding motion of a shell-like structure around the southern nucleus.
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.
The Optical Structure of the Starburst Galaxy M82. II. Nebular Properties of the Disk and Inner Wind
The Astrophysical Journal, 2009
In this second paper of the series, we present the results from optical Gemini-North GMOS-IFU and WIYN DensePak IFU spectroscopic observations of the starburst and inner wind zones of M82, with a focus on the state of the T ∼ 10 4 K ionized interstellar medium. Our electron density maps show peaks of a few 1000 cm −3 (implying very high thermal pressures), local small spatial-scale variations, and a fall-off in the minor axis direction. We discuss the implications of these results with regards to the conditions/locations that may favour the escape of individual cluster winds that ultimately power the large-scale superwind.
GALACTIC WIND IN THE NEARBY STARBURST GALAXY NGC 253 OBSERVED WITH THE KYOTO3DII FABRY-PEROT MODE
The Astrophysical Journal, 2009
We have observed the central region of the nearby starburst galaxy NGC 253 with the Kyoto Tridimensional Spectrograph II (Kyoto3DII) Fabry-Perot mode in order to investigate the properties of its galactic wind. Since this galaxy has a large inclination, it is easy to observe its galactic wind. We produced the Hα, [N II]λ6583, and [S II]λλ6716,6731 images, as well as those line ratio maps. The [N II]/Hα ratio in the galactic wind region is larger than those in H II regions in the galactic disk. The [N II]/Hα ratio in the southeastern filament, a part of the galactic wind, is the largest and reaches about 1.5. These large [N II]/Hα ratios are explained by shock ionization/excitation. Using the [S II]/Hα ratio map, we spatially separate the galactic wind region from the starburst region. The kinetic energy of the galactic wind can be sufficiently supplied by supernovae in a starburst region in the galactic center. The shape of the galactic wind and the line ratio maps are non-axisymmetric about the galactic minor axis, which is also seen in M82. In the [N II]λ6583/[S II]λλ6716,6731 map, the positions with large ratios coincide with the positions of star clusters found in the Hubble Space Telescope (HST) observation. This means that intense star formation causes strong nitrogen enrichment in these regions. Our unique data of the line ratio maps including [S II] lines have demonstrated their effectiveness for clearly distinguishing between shocked gas regions and starburst regions, determining the extent of galactic wind and its mass and kinetic energy, and discovering regions with enhanced nitrogen abundance.
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."
The Astrophysical Journal, 1999
We report ASCA GIS and SIS observations of the nearby (D = 11.6 Mpc), nearly edge-on, starburst galaxy NGC 2146. These X-ray spectral data complement ROSAT PSPC and HRI imaging discussed by The broad band (0.6-9 keV) X-ray spectrum of NGC 2146 is best described by a two component model: the soft X-ray emission with a Raymond-Smith thermal plasma model having a temperature of kT ∼ 0.8 keV; the hard X-ray emission with a thermal plasma model having kT ∼ 8 keV or a power-law model having a photon index of ∼ 1.7. We do not find compelling evidence of substantial excess absorption above the Galactic value. The total luminosities of NGC 2146 in the soft (0.5 -2.0 keV), hard (2-10 keV) and broad (0.5-10.0 keV) energy bands are ∼ 1.3 × 10 40 , ∼ 1.8 × 10 40 and ∼ 3.1 × 10 40 ergs sec −1 , respectively. The soft (hard) thermal component provides about 30% (70%) of the total luminosity in the 0.5 -2.0 keV energy band, while in the 2-10 keV energy range only the hard component plays a major role.