Документ взят из кэша поисковой машины. Адрес оригинального документа : http://www.atnf.csiro.au/research/LVmeeting/posters/LChomiuk-poster.pdf Дата изменения: Thu Jul 5 03:51:29 2007 Дата индексирования: Sun Dec 23 09:43:18 2007 Кодировка: Поисковые слова: релятивистское движение

Supernova Remnant Populations in Nearby Star-Forming Galaxies
Laura Chomiuk & Eric Wilcots, University of Wisconsin--Madison
NGC 628 NGC 3184 NGC 3631

20 cm radio continuum maps obtained at the VLA in its B configuration (~4" resolution). These maps are some of the deepest ever observed (rms noise ~ 0.015 mJy/beam). Maps of similar depth and resolution were also obtained at 6cm. Radio SNRs are marked by circles.

Identifying Radio Supernova Remnants (SNRs)
The SNRs marked in the above maps were chosen to satisfy three criteria: · Integrated 20 cm flux density greater than 3x the local noise · Nonthermal spectral index: = - ln (S20cm / S6cm) / ln ( Needed to separate SNRs from HII regions
20cm/

Why do more luminous galaxies host more luminous SNRs?
· Does the nature of SN feedback vary between galaxies? i.e., Do more luminous galaxies transform star formation energy into cosmic ray energy more efficiently? · Or- is it merely an effect of sampling (more luminous galaxies tend to have higher SF rates (SFRs ), and more opportunity to form bright SNRs ?)



6cm)

> 0.2

· Spatially coincident with H emission in a narrow band image Needed to separate SNRs from background sources (higherredshift AGN will have H shifted out of the filter)

SNR Luminosity Functions

Luminosities of the brightest SNRs are most tightly correlated with SFR.

In the future...
The cosmic ray energy coming from a SNR scales as L equipartition ), where L = SNR luminosity.
4/7

(assuming

If the cosmic ray energy scales linearly with SFR, then we should observe LSNR SFR 7/4 But we need L SNR, an unknown statistic which can robustly characterize the luminosity of a SNR population. We still know very little about the true shape of SNR LFs. NGC 6946- Lacey & Duric (2001); M33- Gordon et al. (1999); LMC and SMC- Filipovic et al. (1998); NGC 7793- Pannuti et al. (2002); NGC 300Pannuti et al. (2000)

A Mysterious Donut!
The central ~1.5 kpc of NGC 3631 is vigorously forming stars. Why is synchrotron emission avoiding the inner 300 pc?

20 cm Radio Continuum, 3.5 " resolution

6 cm Radio Continuum, 3.5 " resolution

21 cm HI Moment 0, 14.0 " resolution

Self absorption?

The brightest SNRs in luminous spirals emit 10-100 times more light @ 20cm than the brightest SNRs in lower luminosity galaxies!
Narrow-band H , 1.5 " resolution Diffuse X-ray, 4.0" resolution

A wind advecting away cosmic rays? A Superbubble ? Molecular gas so dense that cosmic rays can not diffuse into it?

(We assume the jet structure is a background AGN.)