Properties of spheroidal post mergers in the local Universeicg.port.ac.uk/~mastersk/GalaxyZoo/Carpineti_AAS218talk.pdfConclusions • Our sample have strong similarities such as morphology

Properties of spheroidal post-mergers in the local Universe

Alfredo Carpineti

Collaborators: Sugata KavirajDaniel DargChris LintottKevin Schawinskiand the Galaxy Zoo Team

24th May 2011

Thursday, 2 June 2011

Why study galaxy mergers?

Hierarchical galaxy formation

•Small scale structure such as shells, ripples and tails (van Dokkum 2005)

•Elliptical non gas-deficient (Sarzi et al. 05)

•Recent star formation and UV colours (Kaviraj et al. 08)

Mergers are a fundamental mechanism to drive star formation episodes, black hole growth and alter galaxy

morphology

Mergers and Early-type galaxies


The GZ Mergers CatalogueGalaxy Zoo (GZ) is an interface on the www for the visual classification of SDSS Galaxies

by the general public.Each SDSS galaxy classified 80 times by

eye

3003 Binary Mergers

370 post-mergers


Spheroidal post-mergers

30 Galaxies from the PM catalogue (visually selected)

FracDev in r band over 0.5 (sanity check)



Spheroidal Post-mergers

Mass range from 1010.3 to 1011.7 M☉

Local universe z < 0.096


Local Environment of the sampleρ(ra, dec, z, σ) is an environment parameter

25% in the field environment, the vast majority in groups


Emission line Activity in the sample

26% Quiescent - 16% LINER - 16% Star forming - 42% Seyfert

Significant difference from the GZ Merger Catalogue and the elliptical control sample

16%

16%

26%

42%

Quiescent Star Forming LINER Seyfert

37%

43%

6%14%

73%

6%9%12%

Mergers Catalogue Post-merger sample Early-type Control Group Thursday, 2 June 2011

Reconstructing the progenitorsComparison between SPM and Merger population.

Mass ratio 1:1.5 to 1:3 (Major Mergers)

SPM have in general redder colours


Reconstructing the progenitors

Using synthetic SED to compare the optical colours

If we can give a reasonable estimate of the star-forming fraction, we can distinguish between possible

progenitor cases.


Reconstructing the progenitors



Conclusions• Our sample have strong similarities such as morphology and emission line activities with the

general early-type galaxies.

• The vast majority of the SPMs inhabit low-density environments (groups and the field), consistent with the expectation that the high peculiar velocities in high-density environments make conditions difficult for galaxy merging

• Our SPM sample is bluer that the a control sample of early-type galaxies and early-type mergers but redder, on average, than the merging population, indicating that the peak of star formation activity takes place during the merger phase.

• 84% of the SPMs exhibit emission-line activity. 42% show Seyfert-like emission, 26% are LINERs and 16% are classified as star-forming, indicating that the AGN peaks in the post-merger phase.

• Comparisons with synthetic SED and mergers population shows that the majority of the SPM sample are the products of major mergers in which at least one of the progenitors is a late-type galaxy.


Documents

Properties of spheroidal post mergers in the local Universeicg.port.ac.uk/~mastersk/GalaxyZoo/Carpineti_AAS218talk.pdfConclusions • Our sample have strong similarities such as morphology