Radio studies of the ionized gas in the nucleus of M82

Seaquist, E. R.; Bell, Marvin; Bignell, R. C.

doi:10.1086/163322

Cited by 34 publications

(25 citation statements)

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“…In M82, high pressures have been inferred from the [S iii] doublet (Houck et al 1984;Smith et al 2006), from fine structure lines in the far-infrared (Lugten et al 1986;Duffy et al 1987), and from the non-thermal radio continuum (Schaaf et al 1989). After certain assumptions, pressures can be inferred by combining observations of radio recombination lines and the associated free-free emission (Rodriguez & Chaisson 1980;Seaquist et al 1985). The intrinsically higher resolution of linked radio receivers should allow the pressure profile to be traced to the smallest VLBI spatial scales.…”

Section: Discussionmentioning

confidence: 99%

THREE-DIMENSIONAL INTEGRAL FIELD OBSERVATIONS OF 10 GALACTIC WINDS. I. EXTENDED PHASE (≳10 Myr) OF MASS/ENERGY INJECTION BEFORE THE WIND BLOWS

Sharp

Bland-Hawthorn

2010

ApJ

244

282

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In recent years, we have come to recognize the widespread importance of large-scale winds in the life cycle of galaxies. The onset and evolution of a galactic wind is a highly complex process which must be understood if we are to understand how energy and metals are recycled throughout the galaxy and beyond. Here we present three-dimensional spectroscopic observations of a sample of 10 nearby galaxies with the AAOmega-SPIRAL integral-field spectrograph on the 3.9 m Anglo-Australian Telescope, the largest survey of its kind to date. The double-beam spectrograph provides spatial maps in a range of spectral diagnostics:, 6731. We demonstrate that these flows can often separate into highly ordered structures through the use of ionization diagnostics and kinematics. All of the objects in our survey show extensive wind-driven filamentation along the minor axis, in addition to large-scale disk rotation. Our sample can be divided into either starburst galaxies or active galactic nuclei (AGNs), although some objects appear to be a combination of these. The total ionizing photon budget available to both classes of galaxies is sufficient to ionize all of the windblown filamentation out to large radius. We find, however, that while AGN photoionization always dominates in the wind filaments, this is not the case in starburst galaxies where shock ionization dominates. This clearly indicates that after the onset of star formation, there is a substantial delay ( 10 Myr) before a starburst wind develops. We show why this behavior is expected by deriving "ionization" and dynamical timescales for both AGNs and starbursts. We establish a sequence of events that lead to the onset of a galactic wind. The clear signature provided by the ionization timescale is arguably the strongest evidence yet that the starburst phenomenon is an impulsive event. A well-defined ionization timescale is not expected in galaxies with a protracted history of circumnuclear star formation. Our three-dimensional data provide important templates for comparisons with high-redshift galaxies.

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Section: Discussionmentioning

confidence: 99%

THREE-DIMENSIONAL INTEGRAL FIELD OBSERVATIONS OF 10 GALACTIC WINDS. I. EXTENDED PHASE (≳10 Myr) OF MASS/ENERGY INJECTION BEFORE THE WIND BLOWS

Sharp

Bland-Hawthorn

2010

ApJ

244

282

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“…We therefore adopt 250 pc as the radius and 100 pc as the scale height of the modeled starburst region. Other studies find radio scale heights of 50-200 pc (Klein et al 1988;Seaquist et al 1985). Values for the wind speed vary; however, Greve (2004) find that the wind accelerates over a 200 pc scale height to 400 km s −1 and Westmoquette et al (2009) find Hα FWHM of 100-300 km s −1 in the inner few hundred parsecs.…”

Section: M82mentioning

confidence: 94%

Diffuse Hard X-Ray Emission in Starburst Galaxies as Synchrotron From Very High Energy Electrons

Lacki

Thompson

2012

ApJ

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The origin of the diffuse hard X-ray (2-10 keV) emission from starburst galaxies is a long-standing problem. We suggest that synchrotron emission of 10-100 TeV electrons and positrons (e ± ) can contribute to this emission, because starbursts have strong magnetic fields. We consider three sources of e ± at these energies: (1) primary electrons directly accelerated by supernova remnants, (2) pionic secondary e ± created by inelastic collisions between cosmic ray (CR) protons and gas nuclei in the dense interstellar medium of starbursts, and (3) pair e ± produced between the interactions between 10 and 100 TeV γ -rays and the intense far-infrared (FIR) radiation fields of starbursts. We create one-zone steady-state models of the CR population in the Galactic center (R 112 pc), NGC 253, M82, and Arp 220's nuclei, assuming a power-law injection spectrum for electrons and protons. We consider different injection spectral slopes, magnetic field strengths, CR acceleration efficiencies, and diffusive escape times, and include advective escape, radiative cooling processes, and secondary and pair e ± . We compare these models to extant radio and GeV and TeV γ -ray data for these starbursts, and calculate the diffuse synchrotron X-ray and inverse Compton (IC) luminosities of these starbursts in the models which satisfy multiwavelength constraints. If the primary electron spectrum extends to ∼PeV energies and has a proton/electron injection ratio similar to the Galactic value, we find that synchrotron emission contributes 2%-20% of their unresolved, diffuse hard X-ray emission. However, there is great uncertainty in this conclusion because of the limited information on the CR electron spectrum at these high energies. IC emission is likewise a minority of the unresolved X-ray emission in these starbursts, from 0.1% in the Galactic center to 10% in Arp 220's nuclei, with the main uncertainty being the starbursts' magnetic field. We also model generic starbursts, including submillimeter galaxies, in the context of the FIR-X-ray relation, finding that anywhere between 0% and 16% of the total hard X-ray emission is synchrotron for different parameters, and up to 2% in the densest starbursts assuming an E −2.2 injection spectrum and a diffusive escape time of 10 Myr (E/3 GeV) −1/2 (h/100 pc). Neutrino observations by IceCube and TeV γ -ray data from HESS, VERITAS, and CTA can further constrain the synchrotron X-ray emission of starbursts. Our models do not constrain the possibility of hard, second components of primary e ± from sources like pulsars in starbursts, which could enhance the synchrotron X-ray emission further.

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“…Both the energy and mass outflow rates can be estimated from the momentum flux, however, they depend upon the unknown velocity of the wind fluid. For typical values for superwinds of v w = 1000−3000 km s −1 (Seaquist et al 1985;Hopkins et al 2013; HAM90) we estimate a total energy flux oḟ …”

Section: Energetics Of the Superwind Fluidmentioning

confidence: 99%

The Mice at play in the CALIFA survey

Wild

Rosales-Ortega

Falcón-Barroso

et al. 2014

A&A

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We present optical integral field spectroscopy (IFS) observations of the Mice, a major merger between two massive ( 10 11 M ) gas-rich spirals NGC 4676A and B, observed between first passage and final coalescence. The spectra provide stellar and gas kinematics, ionised gas properties, and stellar population diagnostics, over the full optical extent of both galaxies with ∼1.6 kpc spatial resolution. The Mice galaxies provide a perfect case study that highlights the importance of IFS data for improving our understanding of local galaxies. The impact of first passage on the kinematics of the stars and gas has been significant, with strong bars most likely induced in both galaxies. The barred spiral NGC 4676B exhibits a strong twist in both its stellar and ionised gas disk. The edge-on disk galaxy NGC 4676A appears to be bulge free, with a strong bar causing its "boxy" light profile. On the other hand, the impact of the merger on the stellar populations has been minimal thus far. By combining the IFS data with archival multiwavelength observations we show that star formation induced by the recent close passage has not contributed significantly to the total star formation rate or stellar mass of the galaxies. Both galaxies show bicones of high ionisation gas extending along their minor axes. In NGC 4676A the high gas velocity dispersion and Seyfert-like line ratios at large scaleheight indicate a powerful outflow. Fast shocks (v s ∼ 350 km s −1 ) extend to ∼6.6 kpc above the disk plane. The measured ram pressure (P/k = 4.8 × 10 6 K cm −3 ) and mass outflow rate (∼8−20 M yr −1 ) are similar to superwinds from local ultra-luminous infrared galaxies, although NGC 4676A only has a moderate infrared luminosity of 3 × 10 10 L . Energy beyond what is provided by the mechanical energy of the starburst appears to be required to drive the outflow. Finally, we compare the observations to mock kinematic and stellar population maps extracted from a hydrodynamical merger simulation. The models show little enhancement in star formation during and following first passage, in agreement with the observations. We highlight areas where IFS data could help further constrain the models.

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Radio studies of the ionized gas in the nucleus of M82

Cited by 34 publications

References 0 publications

THREE-DIMENSIONAL INTEGRAL FIELD OBSERVATIONS OF 10 GALACTIC WINDS. I. EXTENDED PHASE (≳10 Myr) OF MASS/ENERGY INJECTION BEFORE THE WIND BLOWS

THREE-DIMENSIONAL INTEGRAL FIELD OBSERVATIONS OF 10 GALACTIC WINDS. I. EXTENDED PHASE (≳10 Myr) OF MASS/ENERGY INJECTION BEFORE THE WIND BLOWS

Diffuse Hard X-Ray Emission in Starburst Galaxies as Synchrotron From Very High Energy Electrons

The Mice at play in the CALIFA survey

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