Skip to main content Accessibility help
×
Home
Hostname: page-component-99c86f546-pkshj Total loading time: 0.493 Render date: 2021-11-30T01:17:10.143Z Has data issue: true Feature Flags: { "shouldUseShareProductTool": true, "shouldUseHypothesis": true, "isUnsiloEnabled": true, "metricsAbstractViews": false, "figures": true, "newCiteModal": false, "newCitedByModal": true, "newEcommerce": true, "newUsageEvents": true }

Book contents

Physical Properties of Giant Extragalactic HII Regions

Published online by Cambridge University Press:  10 November 2010

G. Tenorio-Tagle
Affiliation:
Instituto de Astrofísica de Canarias, Tenerife
A. I. Diaz
Affiliation:
Depto. de Física Teórica, Universidad Autónoma de Madrid, 28049-Cantoblanco, Spain
Get access

Summary

A discussion of the determination of the “functional parameters” of Giant Extragalactic HII Regions is made for a wide range of physical conditions of the ionized gas. These functional parameters which are found to be the effective temperature of the ionizing radiation, the ionization parameter and the gas metallicity, are then traslated into physical properties of the ionizing star clusters – age, total mass and metal content – through the use of evolutionary models. These models combine evolutionary synthesis techniques with a well-tested photoionization code, CLOUDY, to obtain emission line intensities that can be compared directly with observations. From this comparison some conclusions about the general properties of the ionizing clusters can be extracted.

Introduction

The term Giant Extragalactic HII Region (GEHR) usually refers to outstandingly large and luminous HII regions that are therefore easily observable in external galaxies, mainly on the discs of late-type spirals and in irregulars. Their size, characterized by mean diameters measured on Hα images, can be as large as 1 kpc. Their Hα emission luminosity, which can reach 1041 erg s−1, translates into a number of ionizing photons betbeen 1050 and 1053 s−1. This high number of ionizing photons cannot originate in a single star, which would provide about 1049 at most, but requires the presence of a young star cluster.

In the few instances in which GEHR can be spatially resolved, observations reveal a core-halo structure with the core showing detailed substructure.

Type
Chapter
Information
Violent Star Formation
From 30 Doradus to QSOs
, pp. 105 - 116
Publisher: Cambridge University Press
Print publication year: 1994

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)
8
Cited by

Send book to Kindle

To send this book to your Kindle, first ensure no-reply@cambridge.org is added to your Approved Personal Document E-mail List under your Personal Document Settings on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part of your Kindle email address below. Find out more about sending to your Kindle.

Note you can select to send to either the @free.kindle.com or @kindle.com variations. ‘@free.kindle.com’ emails are free but can only be sent to your device when it is connected to wi-fi. ‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.

Find out more about the Kindle Personal Document Service.

Available formats
×

Send book to Dropbox

To send content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about sending content to Dropbox.

Available formats
×

Send book to Google Drive

To send content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about sending content to Google Drive.

Available formats
×