Very Large Telescope observations of nearby dwarf irregular galaxies

Abstract

Observations of the Local Group dwarf irregular galaxies Aquarius dIrr, IC 1613, LGS 3, NGC 6822, Pegasus dIrr, Phoenix dIrr, Sagittarius dIrr, and WLM were made, using the Visible Multi-Object Spectrograph (VIMOS) on the Very Large Telescope (VLT). The data consists of 198 V and 192 I -band images. A photometric point-source catalogue was made from 186 of these image pairs, with aperture photometry performed using a combination of python, esorex and SExtractor. Astrometric and photometric corrections were determined using the produced catalogue and external datasets. For these eight dwarf irregular galaxies there were 241,999 source detections. The sensitivity limit was estimated to be V ~ 24 mag and I ~ 22 mag, in terms of depth: these observations are among the most sensitive of their type. Colour-magnitude diagrams were generated and relevant isochrones overlain to highlight stellar populations. The VLT data were also crossmatched with 3.6 and 4.5 um Spitzer data from the DUSTiNGS survey's Good Source Catalogue. 68 DUSTiNGS variable sources were located in the VLT catalogue, with some notable variation in magnitudes, which was attributed to the large variability of these sources. Two of the variable sources located in the VLT catalogue for IC 1613 were found in a dataset from Menzies, Whitelock & Feast (2015). This catalogue will be useful for those studying metal-poor environments and analogues for the early Universe. This data will also be useful for follow up studies attempting to separate carbon and oxygen-rich stars and studies using the upcoming James Webb Space Telescope.

Date of Award	1 Aug 2018
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Gary Fuller (Supervisor) & Iain Mcdonald (Supervisor)