Hubble Space Telescope Pixel Analysis of the Interacting Face-on Spiral Galaxy NGC 5194 (M51A)

Abstract

A pixel analysis is carried out on the interacting face-on spiral galaxy NGC 5194 (M51A), using the HST/ACS images in the F435W, F555W and F814W (BVI) bands. After 4x4 binning of the HST/ACS images to secure a sufficient signal-to-noise ratio for each pixel, we derive several quantities describing the pixel color-magnitude diagram (pCMD) of NGC 5194: blue/red color cut, red pixel sequence parameters, blue pixel sequence parameters and blue-to-red pixel ratio. The red sequence pixels are mostly older than 1 Gyr, while the blue sequence pixels are mostly younger than 1 Gyr, in their luminosity-weighted mean stellar ages. The color variation in the red pixel sequence from V = 20 mag arcsec^(-2) to V = 17 mag arcsec^(-2) corresponds to a metallicity variation of Δ[Fe/H] ~ 2 or an optical depth variation of Δτ_V ~ 4 by dust, but the actual sequence is thought to originate from the combination of those two effects. At V < 20 mag arcsec^(-2), the color variation in the blue pixel sequence corresponds to an age variation from 5 Myr to 300 Myr under the assumption of solar metallicity and τ_V = 1. To investigate the spatial distributions of stellar populations, we divide pixel stellar populations using the pixel color-color diagram and population synthesis models. As a result, we find that the pixel population distributions across the spiral arms agree with a compressing process by spiral density waves: dense dust \rightarrow newly-formed stars. The tidal interaction between NGC 5194 and NGC 5195 appears to enhance the star formation at the tidal bridge connecting the two galaxies. We find that the pixels corresponding to the central active galactic nucleus (AGN) area of NGC 5194 show a tight sequence at the bright-end of the pCMD, which are in the region of R ~ 100 pc and may be a photometric indicator of AGN properties.

27 pages, 20 figures, accepted for publication in ApJ

References in corpus (14)

• Early-type galaxies at large galactocentric radii - II. Metallicity gradients, and the [Z/H]--mass, [alpha/Fe]--mass relations
• A spectroscopic survey of dwarf galaxies in the Coma Cluster: Stellar populations, environment and downsizing
• Radial Dependence of the Pattern Speed of M51
• Spatially Resolved Galaxy Star Formation and its Environmental Dependence I
• HII Region Luminosity Function of the Interacting Galaxy M51
• A Catalog of Bright Star Clusters in the Interacting Galaxy M51
• The Nature of Blue Early-Type Galaxies in the Goods Fields
• The nature of the SDSS galaxies in various classes based on morphology, colour and spectral features -- I. Optical properties
• Structure Through Colour: A Pixel Approach Towards Understanding Galaxies
• The Stellar Populations of Bright Coma Cluster Galaxies
• Mapping the Recent Star Formation History of the Disk of M51
• Spatially Resolved Galaxy Star Formation and its Environmental Dependence II. Effect of the Morphology-Density Relation
• AKARI Near-Infrared Spectroscopy of SDSS-Selected Blue Early-Type Galaxies
• Star formation histories and evolution of 35 brightest E+A galaxies from SDSS DR5

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• AGN feedback in the nucleus of M51
• Deep Imaging of M51: a New View of the Whirlpool's Extended Tidal Debris
• Bayesian isochrone fitting and stellar ages
• Hubble Space Telescope Pixel Analysis of the Interacting S0 Galaxy NGC 5195 (M51B)
• The Evolution of Interacting Spiral Galaxy NGC 5194
• Color Dispersion as an Indicator of Stellar Population Complexity: Insights from the Pixel Color-Magnitude Diagrams of 32 Bright Galaxies in Abell 1139 and Abell 2589
• Pixel Color-Magnitude Diagram Analysis of the Brightest Cluster Galaxies in Dynamically Young and Old Clusters, Abell 1139 and Abell 2589