The Eddington Limit in Cosmic Rays: An Explanation for the Observed Faintness of Starbursting Galaxies

Socrates, Aristotle; Davis, Shane W.; Ramírez-Ruiz, E.

doi:10.1086/590046

Cited by 163 publications

(183 citation statements)

References 41 publications

Supporting

Mentioning

178

Contrasting

Order By: Relevance

“…These values are only 26% larger than in the case of purely thermally driven winds. These estimates seems to be upper limits as we do not include any quenching effect of CRs on star formation (Socrates et al 2008;Samui et al 2009) and the interaction of CRs with mass-loaded gaseous outflows.…”

Section: Magnetization Of the Igmmentioning

confidence: 95%

Magnetic fields in Local Group dwarf irregulars

Chyży

Weżgowiec

Beck

et al. 2011

A&A

116

150

View full text Add to dashboard Cite

Aims. We wish to clarify whether strong magnetic fields can be effectively generated in typically low-mass dwarf galaxies and to assess the role of dwarf galaxies in the magnetization of the Universe. Methods. We performed a search for radio emission and magnetic fields in an unbiased sample of 12 Local Group (LG) irregular and dwarf irregular galaxies with the 100-m Effelsberg telescope at 2.64 GHz. Three galaxies were detected. A higher frequency (4.85 GHz) was used to search for polarized emission in five dwarfs that are the most luminous ones in the infrared domain, of which three were detected. Results. Magnetic fields in LG dwarfs are weak, with a mean value of the total field strength of <4.2 ± 1.8 μG, three times lower than in the normal spirals. The strongest field among all LG dwarfs of 10 μG (at 2.64 GHz) is observed in the starburst dwarf IC 10. The production of total magnetic fields in dwarf systems appears to be regulated mainly by the star-formation surface density (with the power-law exponent of 0.30 ± 0.04) or by the gas surface density (with the exponent 0.47 ± 0.09). In addition, we find systematically stronger fields in objects of higher global star-formation rate. The dwarf galaxies follow a similar far-infrared relationship (with a slope of 0.91 ± 0.08) to that determined for high surface brightness spiral galaxies. The magnetic field strength in dwarf galaxies does not correlate with their maximum rotational velocity, indicating that a small-scale rather than a large-scale dynamo process is responsible for producting magnetic fields in dwarfs. If magnetization of the Universe by galactic outflows is coeval with its metal enrichment, we show that more massive objects (such as Lyman break galaxies) can efficiently magnetize the intergalactic medium with a magnetic field strength of about 0.8 nG out to a distance of 160-530 kpc at redshifts 5-3, respectively. Magnetic fields that are several times weaker and shorter magnetization distances are expected for primordial dwarf galaxies. We also predict that most star-forming local dwarfs might have magnetized their surroundings up to a field strength about 0.1 μG within about a 5 kpc distance. Conclusions. Strong magnetic fields (>6 μG) are observed only in dwarfs of extreme characteristics (e.g. NGC 4449, NGC 1569, and the LG dwarf IC 10). They are all starbursts and more evolved objects of statistically much higher metallicity and global star-formation rate than the majority of the LG dwarf population. Typical LG dwarfs are unsuitable objects for the efficient supply of magnetic fields to the intergalactic medium.

show abstract

Section: Magnetization Of the Igmmentioning

confidence: 95%

Magnetic fields in Local Group dwarf irregulars

Chyży

Weżgowiec

Beck

et al. 2011

A&A

116

150

View full text Add to dashboard Cite

show abstract

“…It is suggested in Ref. 104 that the rate of star formation in galaxies, which is tied to the supernova rate and thus to the cosmic ray acceleration rate, may be inherently self-limiting because too large a cosmic ray pressure would drive the interstellar medium out of the galaxy.…”

Section: Winds and Heatingmentioning

confidence: 99%

The microphysics and macrophysics of cosmic rays

2013

View full text Add to dashboard Cite

This review paper commemorates a century of cosmic ray research, with emphasis on the plasma physics aspects. Cosmic rays comprise only ∼10−9 of interstellar particles by number, but collectively their energy density is about equal to that of the thermal particles. They are confined by the Galactic magnetic field and well scattered by small scale magnetic fluctuations, which couple them to the local rest frame of the thermal fluid. Scattering isotropizes the cosmic rays and allows them to exchange momentum and energy with the background medium. I will review a theory for how the fluctuations which scatter the cosmic rays can be generated by the cosmic rays themselves through a microinstability excited by their streaming. A quasilinear treatment of the cosmic ray–wave interaction then leads to a fluid model of cosmic rays with both advection and diffusion by the background medium and momentum and energy deposition by the cosmic rays. This fluid model admits cosmic ray modified shocks, large scale cosmic ray driven instabilities, cosmic ray heating of the thermal gas, and cosmic ray driven galactic winds. If the fluctuations were extrinsic turbulence driven by some other mechanism, the cosmic ray background coupling would be entirely different. Which picture holds depends largely on the nature of turbulence in the background medium.

show abstract

“…More than 90% of UV and visible radiation from starbursting ULIRGs is absorbed by dust, leaving FIR and radio observations as the most promising way to gain insight on the star formation processes within such systems and better understand the physical connection between the gaseous and relativistic phases of the ISM. Such a connection includes that of feedback processes; the production and expulsion of CRs in galaxies may work to cap their luminosity and star formation intensity (Socrates et al 2008). The outlook for such additional observations appears rather bright; with Herschel and the EVLA on the horizon, increasing the sample size and improving the sensitivity and resolution of the observations, allowing the inclusion of more distant galaxies, should become achievable within a few years.…”

Section: Remaining Issues and Future Prospectsmentioning

confidence: 99%

Connecting Far‐Infrared and Radio Morphologies of Disk Galaxies: Cosmic‐Ray Electron Diffusion After Star Formation Episodes

Murphy

Hélou

Kenney

et al. 2008

ApJ

111

182

View full text Add to dashboard Cite

We present results on the ISM properties of 29 galaxies based on a comparison of Spitzer far-infrared and Westerbork Synthesis Radio Telescope radio continuum imagery. Of these 29 galaxies, 18 are close enough to resolve at P1 kpc scales at 70 m and 22 cm. We extend the approach of our earlier work of smoothing infrared images to approximate cosmic-ray (CR) electron spreading and thus largely reproduce the appearance of radio images. Using a wavelet analysis, we decompose each 70 m image into one component containing the star-forming structures and a second one for the diffuse disk. The components are smoothed separately, and their combination compared to a free-free corrected 22 cm radio image; the scale lengths are then varied to best match the radio and smoothed infrared images. We find that late-type spirals having high amounts of ongoing star formation benefit most from the two-component method. We also find that the disk component dominates for galaxies having low star formation activity, whereas the structure component dominates at high star formation activity. We propose that this result arises from an age effect rather than from differences in CR electron diffusion due to varying ISM parameters. The bulk of the CR electron population in actively star-forming galaxies is significantly younger than that in less active galaxies due to recent episodes of enhanced star formation; these galaxies are observed within $10 8 yr since the onset of the most recent star formation episode. The sample irregulars have anomalously low best-fit scale lengths for their surface brightnesses compared to the rest of the sample spirals, which we attribute to enhanced CR electron escape.

show abstract

The Eddington Limit in Cosmic Rays: An Explanation for the Observed Faintness of Starbursting Galaxies

Cited by 163 publications

References 41 publications

Magnetic fields in Local Group dwarf irregulars

Magnetic fields in Local Group dwarf irregulars

The microphysics and macrophysics of cosmic rays

Connecting Far‐Infrared and Radio Morphologies of Disk Galaxies: Cosmic‐Ray Electron Diffusion After Star Formation Episodes

Contact Info

Product

Resources

About