Facial reconstruction

Search LJMU Research Online

Browse Repository | Browse E-Theses

Constraining the escape fraction of ionizing photons from H II regions within NGC 300: A concept paper

Niederhofer, F and Hilker, M and Bastian, N and Ercolano, B (2016) Constraining the escape fraction of ionizing photons from H II regions within NGC 300: A concept paper. ASTRONOMY & ASTROPHYSICS, 592 (A47). ISSN 1432-0746

Full text not available from this repository. Please see publisher or open access link below:
Open Access URL: https://arxiv.org/abs/1606.01144 (Accepted version)

Abstract

Using broadband photometry from the Hubble Space Telescope in combination with Very Large Telescope narrowband Hα observations of the nearby spiral galaxy NGC 300, we explore a method for estimating the escape fractions of hydrogen-ionizing photons from H ii regions within this galaxy. Our goal in this concept study is to evaluate the spectral types of the most massive stars using the broadband data and estimating their ionizing photon output with the help of stellar atmosphere models. A comparison with the Hα flux that gives the amount of ionized gas in the H ii region provides a measure of the escape fraction of ionizing photons from that region. We performed some tests with a number of synthetic young clusters with varying parameters to assess the reliability of the method. However, we found that the derived stellar spectral types and consequently the expected ionizing photon luminosity of a region is highly uncertain. The tests also show that on one hand we tended to overestimate the integrated photon output of a region for young ages and low numbers of stars, and on the other hand we mostly underestimated the combined ionizing luminosity for a large stellar number and older cluster ages. We conclude that the proposed method of using stellar broadband photometry to infer the leakage of ionizing photons from H ii regions is highly uncertain and dominated by the errors of the resulting stellar spectral types. Therefore this method is not suitable. Stellar spectra are needed to reliably determine the stellar types and escape fractions. Studies to this end have been carried out for the Magellanic Clouds.

Item Type: Article
Uncontrolled Keywords: 0201 Astronomical And Space Sciences
Subjects: Q Science > QB Astronomy
Divisions: Astrophysics Research Institute
Publisher: EDP SCIENCES S A
Related URLs:
Date Deposited: 06 Apr 2017 11:43
Last Modified: 06 Apr 2017 11:43
DOI or Identification number: 10.1051/0004-6361/201527819
URI: http://researchonline.ljmu.ac.uk/id/eprint/6221

Actions (login required)

View Item View Item