The Structure and Stellar Content of the Central Region of M33

Abstract

Using Gemini QuickStart infrared observations of the central 22" of M33, we analyze the stellar populations in this controversial region. Based on the slope of the giant branch we estimate the mean metallicity to be -0.26+/-0.27, and from the luminosities of the most luminous stars, we estimate that there were two bursts of star formation ~2 and ~0.5 Gyr ago. We show that the stellar luminosity function not only has a different bright end cutoff, but also a significantly different slope than that of the Galactic bulge, and suggest that this difference is due to the young stellar component in M33. We combine our infrared Gemini data with optical HST-WFPC2 measurements revealing a CMD populated with young, intermediate, and old age stellar populations. Using surface brightness profiles from 0.1" to 18', we perform simple decompositions and show that the data are best fit by a three-component, core + bulge + disk model. Finally, we find no evidence for radial variations of the stellar populations in the inner 3"-10" of M33 based on a spatial analysis of the color-magnitude diagrams and luminosity functions.

22 pages, including 22 figures and 4 tables. Submitted to the Astronomical Journal

Cited by in corpus (23)

• Masses of star clusters in the nuclei of bulge-less spiral galaxies
• Stellar populations in the nuclei of late-type spiral galaxies
• On the Origin of Nuclear Star Clusters in Late Type Spiral Galaxies
• Infrared stellar populations in the central parts of the Milky Way galaxy
• The metallicity gradient of M 33: chemical abundances of HII regions
• Metal production in M33: space and time variations
• Discovery of a relationship between spiral arm morphology and supermassive black hole mass in disk galaxies
• The distance of M33 and the stellar population in its outskirts
• The planetary nebula population of M33 and its metallicity gradient: A look into the galaxy's distant past
• Was the Andromeda Stream Produced by a Disk Galaxy?
• The Panchromatic Hubble Andromeda Treasury: Triangulum Extended Region (PHATTER) I. Ultraviolet to Infrared Photometry of 22 Million Stars in M33
• The building up of the disk galaxy M33 and the evolution of the metallicity gradient
• The Stellar Populations of M33's Outer Regions III: Star Formation History
• The Stellar Populations of M33's Outer Regions IV: Inflow History and Chemical Evolution
• The stellar content of the isolated transition dwarf galaxy DDO210
• A Search for Dark Matter Annihilation with the Whipple 10m Telescope
• The UK Infrared Telescope M33 monitoring project. II. The star formation history in the central square kiloparsec
• AGB stars as tracers of metallicity and mean age across M33
• The Stellar Populations of M33's Outer Regions II: Deep ACS Imaging
• The Disk and Extraplanar Environment of NGC 247
• Dwarf elliptical galaxies in Centaurus A group: stellar populations in AM 1339-445 and AM 1343-452
• UBVI Surface Photometry of the Spiral Galaxy NGC 300 in the Sculptor Group
• The infrared imaging spectrograph (IRIS) for TMT: the science case