On the Nature of the HII Regions in the Extended Ultraviolet Disc of NGC 4625

Details On the Nature of the HII Regions in the Extended Ultraviolet Disc of NGC 4625 On the Nature of the HII Regions in the Extended Ultraviolet Disc of NGC 4625

2010-11-09

arxiv.org/abs/1011.1967v1

Astronomy and Astrophysics

Astrophysics

Cosmology and Extragalactic Astrophysics

14 pages, 8 figures, accepted for publication in MNRAS

Scientific paper

Using deep Subaru/FOCAS spectra of 34 HII regions in both the inner and outer parts of the extended ultraviolet (XUV) disc galaxy NGC 4625 we have measured an abundance gradient out to almost 2.5 times the optical isophotal radius. We applied several strong line abundance calibrations to determine the HII region abundances, including R23, [NII]/[OII], [NII]/Ha as well as the [OIII]4363 auroral line, which we detected in three of the HII regions. We find that at the transition between the inner and outer disc the abundance gradient becomes flatter. In addition, there appears to be an abundance discontinuity in proximity of this transition. Several of our target HII regions appear to deviate from the ionisation sequence defined in the [NII]/Ha vs. [OIII]/Hb diagnostic diagram by bright extragalactic HII regions. Using theoretical models we conclude that the most likely explanations for these deviations are either related to the time evolution of the HII regions, or stochastic variations in the ionising stellar populations of these low mass HII regions, although we are unable to distinguish between these two effects. Such effects can also impact on the reliability of the strong line abundance determinations.

Affiliated with

Also associated with

No associations

Rating

On the Nature of the HII Regions in the Extended Ultraviolet Disc of NGC 4625 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 On the Nature of the HII Regions in the Extended Ultraviolet Disc of NGC 4625, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and On the Nature of the HII Regions in the Extended Ultraviolet Disc of NGC 4625 will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-492592