VLA Detection of RRLs from the radio nucleus of NGC 253 : Ionization by a weak AGN, an obscured SSC or a compact SNR ?

Details VLA Detection of RRLs from the radio nucleus of NGC 253 : Ionization by a weak AGN, an obscured SSC or a compact SNR ? VLA Detection of RRLs from the radio nucleus of NGC 253 : Ionization by a weak AGN, an obscured SSC or a compact SNR ?

2002-04-03

arxiv.org/abs/astro-ph/0204051v1

Astronomy and Astrophysics

Astrophysics

9 pages, 4 figures, 4 tables. Accepted for publication in ApJ

Scientific paper

We have imaged the H92alpha and H75alpha radio recombination line (RRL) emissions from the starburst galaxy NGC 253 with a resolution of ~4 pc. The peak of the RRL emission at both frequencies coincides with the unresolved radio nucleus. Both lines observed towards the nucleus are extremely wide, with FWHM of ~200 km /s. Modeling the RRL and radio continuum data for the radio nucleus shows that the lines arise in gas whose density is ~10^4 \cc and mass is few thousand Msun, which requires an ionizing flux of (6-20)x10^{51} photons /s. We consider a SNR expanding in a dense medium, a star cluster and also an AGN as potential ionizing sources. Based on dynamical arguments, we rule out an SNR as a viable ionizing source. A star cluster model was considered and the dynamics of the ionized gas in a stellar-wind driven structure was investigated. Such a model is consistent with the properties of the ionized gas only for a cluster younger than ~10^5 years. The existence of such a young cluster at the nucleus seems improbable. The third model assumes the ionizing source to be an AGN at the nucleus. In this model, it was shown that the observed X-ray flux is too weak to account for the required ionizing photon flux. However, the ionization requirement can be explained if the accretion disk is assumed to have a Big Blue Bump in its spectrum. Hence, we favor an AGN at the nucleus as the source responsible for ionizing the observed RRLs. A hybrid model consisting of a inner ADAF disk and an outer thin disk is suggested, which could explain the radio, UV and the X-ray luminosities of the nucleus.

Affiliated with

Also associated with

No associations

Rating

VLA Detection of RRLs from the radio nucleus of NGC 253 : Ionization by a weak AGN, an obscured SSC or a compact SNR ? does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with VLA Detection of RRLs from the radio nucleus of NGC 253 : Ionization by a weak AGN, an obscured SSC or a compact SNR ?, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and VLA Detection of RRLs from the radio nucleus of NGC 253 : Ionization by a weak AGN, an obscured SSC or a compact SNR ? will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-339833