2017ApJ...838...68K

Query : 2017ApJ...838...68K

2017ApJ...838...68K - Astrophys. J., 838, 68-68 (2017/March-3)

Spectral energy distribution and radio halo of NGC 253 at low radio frequencies.

KAPINSKA A.D., STAVELEY-SMITH L., CROCKER R., MEURER G.R., BHANDARI S., HURLEY-WALKER N., OFFRINGA A.R., HANISH D.J., SEYMOUR N., EKERS R.D., BELL M.E., CALLINGHAM J.R., DWARAKANATH K.S., FOR B.-Q., GAENSLER B.M., HANCOCK P.J., HINDSON L., JOHNSTON-HOLLITT M., LENC E., McKINLEY B., MORGAN J., PROCOPIO P., WAYTH R.B., WU C., ZHENG Q., BARRY N., BEARDSLEY A.P., BOWMAN J.D., BRIGGS F., CARROLL P., DILLON J.S., EWALL-WICE A., FENG L., GREENHILL L.J., HAZELTON B.J., HEWITT J.N., JACOBS D.J., KIM H.-S., KITTIWISIT P., LINE J., LOEB A., MITCHELL D.A., MORALES M.F., NEBEN A.R., PAUL S., PINDOR B., POBER J.C., RIDING J., SETHI S.K., UDAYA SHANKAR N., SUBRAHMANYAN R., SULLIVAN I.S., TEGMARK M., THYAGARAJAN N., TINGAY S.J., TROTT C.M., WEBSTER R.L., WYITHE S.B., CAPPALLO R.J., DESHPANDE A.A., KAPLAN D.L., LONSDALE C.J., McWHIRTER S.R., MORGAN E., OBEROI D., ORD S.M., PRABU T., SRIVANI K.S., WILLIAMS A. and WILLIAMS C.L.

Abstract (from CDS):

We present new radio continuum observations of NGC 253 from the Murchison Widefield Array at frequencies between 76 and 227 MHz. We model the broadband radio spectral energy distribution for the total flux density of NGC 253 between 76 MHz and 11 GHz. The spectrum is best described as a sum of a central starburst and extended emission. The central component, corresponding to the inner 500 pc of the starburst region of the galaxy, is best modeled as an internally free-free absorbed synchrotron plasma, with a turnover frequency around 230 MHz. The extended emission component of the spectrum of NGC 253 is best described as a synchrotron emission flattening at low radio frequencies. We find that 34% of the extended emission (outside the central starburst region) at 1 GHz becomes partially absorbed at low radio frequencies. Most of this flattening occurs in the western region of the southeast halo, and may be indicative of synchrotron self-absorption of shock-reaccelerated electrons or an intrinsic low-energy cutoff of the electron distribution. Furthermore, we detect the large-scale synchrotron radio halo of NGC 253 in our radio images. At 154-231 MHz the halo displays the well known X-shaped/horn-like structure, and extends out to ∼8 kpc in the z-direction (from the major axis).

Abstract Copyright: © 2017. The American Astronomical Society. All rights reserved.

Journal keyword(s): galaxies: halos - galaxies: individual: NGC 253 - galaxies: starburst - radiation mechanisms: non-thermal - radiation mechanisms: thermal - radio continuum: galaxies - radio continuum: galaxies

Simbad objects: 3

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Number of rows : 3
N Identifier Otype ICRS (J2000)
RA 		ICRS (J2000)
DEC 		Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2026 		#notes
1 NGC 253 SyG 00 47 33.134 -25 17 19.68   8.03   6.94 8.1 ~ 3588 2
2 NAME Scl Group GrG 01 00 06 -33 44.2           ~ 526 0
3 NAME Local Group GrG ~ ~           ~ 9325 0

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