Bernardi, Stefano

The evolutionary path followed by a galaxy shapes its internal structure, and, in particular, its internal colour variation. We present a study of the internal colour variation within galaxies from the Seventh Data Release of the Sloan Digital Sky Survey (SDSS DR7). We statistically study the connection between the internal colour variation and global galactic properties, looking for hints of the recent galactic evolution. Considering only galaxies with good photometry and spectral measurements, we define four luminosity-threshold samples within the redshift range 0.01

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“…which makes the tendency significant. The same tendency has been found in the study by Roche, Bernardi & Hyde (2010) on early-type galaxies.…”

Section: Velocity Dispersion and Stellar Masssupporting

confidence: 89%

“…Median colour gradients are steeper for higher values of R50 (arcsec), for all the defined luminosity-threshold samples. The same tendency has been found in the study by Roche et al (2010) on early-type galaxies. Figure A3.…”

Section: A2 Effect Of the Number Of Annuli Consideredsupporting

confidence: 89%

Colour gradients within SDSS DR7 galaxies: hints of recent evolution

González-Pérez

Castander

Kauffmann

2010

Monthly Notices of the Royal Astronomical Society

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“…Former studies made no selection on the galaxy type (centrals or satellites), and found that colour gradients in massive galaxies are shallower in denser environment (Tamura & Ohta 2000;Ko & Im 2005;La Barbera et al 2005) similarly to our findings, although La Barbera et al (2011) have shown that the optical-IR ∇ g−K is almost independent of the environment. Along the same line, Roche, Bernardi & Hyde (2010) have demonstrated that central galaxies have shallower gradients than normal E/S0 galaxies at the same luminosity.…”

Section: Discussion a N D C O N C L U S I O N Smentioning

confidence: 74%

Population gradients in the Sloan Digital Sky Survey Galaxy Catalogue: the role of merging

Tortora

Napolitano

2012

Monthly Notices of the Royal Astronomical Society

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We investigate the role of the environment on the colour and stellar population gradients in a local sample of ∼3500 central and ∼1150 satellite Sloan Digital Sky Survey (SDSS) early‐type galaxies. The environment is parametrized in terms of the number of satellite galaxies, Ngal, in each group. For central galaxies, we find that both optical colour and mass‐to‐light (M/L) ratio gradients are shallower in central galaxies residing in denser environments (higher Ngal). This trend is driven by metallicity gradients, while age gradients appear to be less dependent on the environment and to have a larger scatter. On the other hand, satellites do not show any differences in terms of the environment. The same results are found if galaxies are classified by central age, and both central and satellite galaxies have shallower gradients if they are older and steeper gradients if younger, satellites being independent of ages. In central galaxies, we show that the observed trends can be explained with the occurrence of dry mergings, which are more numerous in denser environments and producing shallower colour gradients because of more uniform metallicity distributions due to the mixing of stellar populations, while no final clues about merging occurrence can be obtained for satellites. Finally, we discuss all systematics on stellar population fitting and their impact on the final results.

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“…Peletier et al 1990;Saglia et al 2000), while in the recent years, the study of large galaxy samples has mostly focused on the optical regime (e.g. Roche, Bernardi & Hyde 2010;Tortora et al 2010;González-Pérez, Castander & Kauffmann 2011), where one has to contend with the age-metallicity-extinction degeneracy (Worthey 1994). Silva & Elston (1994), and more recently Roediger et al (2011), have found evidence for significant age gradients in ellipticals, while independent works (e.g.…”

Section: Introductionmentioning

confidence: 99%

SPIDER - VII. Revealing the stellar population content of massive early-type galaxies out to 8R_e

Barbera

Ferreras

Carvalho

et al. 2012

Monthly Notices of the Royal Astronomical Society

104

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Radial trends of stellar populations in galaxies provide a valuable tool to understand the mechanisms of galaxy growth. In this paper, we present the first comprehensive analysis of optical–optical and optical–NIR colours, as a function of galaxy mass, out to the halo region (8Re) of early‐type galaxies (ETGs). We select a sample of 674 massive ETGs (M★ ≳ 3 × 1010 M⊙) from the Sloan Digital Sky Survey (SDSS)‐based SPIDER survey. By comparing with a large range of population synthesis models, we derive robust constraints on the radial trends in age and metallicity. Metallicity is unambiguously found to decrease outwards, with a measurable steepening of the slope in the outer regions (Re < R < 8Re). The gradients in stellar age are found to be more sensitive to the models used, but in general, the outer regions of ETGs feature older populations compared to the cores. This trend is strongest for the most massive galaxies in our sample (M★ ≳ 1011 M⊙). Furthermore, when segregating with respect to large‐scale environment, the age gradient is more significant in ETGs residing in higher density regions. These results shed light on the processes leading from the formation of the central core to the growth of the stellar envelope of massive galaxies. The fact that the populations in the outer regions are older and more metal‐poor than in the core suggests a process whereby the envelope of massive galaxies is made up of accreted small satellites (i.e. minor mergers) whose stars were born during the first stages of galaxy formation.

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Bernardi, Stefano

Cited by 16 publications

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Colour gradients within SDSS DR7 galaxies: hints of recent evolution

Colour gradients within SDSS DR7 galaxies: hints of recent evolution

Population gradients in the Sloan Digital Sky Survey Galaxy Catalogue: the role of merging

SPIDER - VII. Revealing the stellar population content of massive early-type galaxies out to 8R_e

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Bernardi, Stefano

Cited by 16 publications

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Colour gradients within SDSS DR7 galaxies: hints of recent evolution

Colour gradients within SDSS DR7 galaxies: hints of recent evolution

Population gradients in the Sloan Digital Sky Survey Galaxy Catalogue: the role of merging

SPIDER - VII. Revealing the stellar population content of massive early-type galaxies out to 8Re

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SPIDER - VII. Revealing the stellar population content of massive early-type galaxies out to 8R_e