Cluster versus Field Elliptical Galaxies and Clues on Their Formation

Bernardi, Mariangela; Renzini, A.; Costa, L. N. da; Wegner, Gary A.; Alonso, M. V.; Pellegrini, P. S.; Rité, C.; Willmer, Christopher N. A.

doi:10.1086/311742

Cited by 150 publications

(209 citation statements)

References 34 publications

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“…1 The medium redshift of formation is , and therefore the z ∼ 2 medium age of the field elliptical galaxies in the HDF-S is ∼11 Gyr. Therefore, as a whole, field elliptical galaxies are only 1-2 Gyr younger than cluster elliptical galaxies, in agreement with the findings by Bernardi et al (1998) who compared the Mg 2 -j 0 relation for field and cluster elliptical galaxies. The main feature of Figure 3 is the continuous formation of field E/S0 galaxies with redshift; we do not find evidence for a single epoch of spheroid formation.…”

Section: Isupporting

confidence: 91%

The Origin of Blue Cores in Hubble Deep Field E/S0 Galaxies

Menanteau

Jiménez

Matteuccí

2001

The Astrophysical Journal

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In this Letter we address the problem of the origin of blue cores and inverse color gradients in early-type galaxies reported in the Hubble Deep Field-North and Hubble Deep Field-South by Menanteau, Abraham, & Ellis. We use a multizone single-collapse model. This model accounts for the observed blue cores by adopting a broad spread in formation redshifts for elliptical galaxies, allowing some of these galaxies to begin forming no more than ∼1 Gyr before the redshift of observation. The single-zone collapse model then produces cores that are bluer than the outer regions because of the increase of the local potential well toward the center, which makes star formation more extended in the central region of the galaxy. We compare the predicted V 606 ϪI 814 (r) color gradients with those observed using the redshift of formation ( ) of the elliptical as the only free parameter.z F We find that the model can account with relatively good agreement for the blue cores and inverse color gradients found in many spheroidals and at the same time for the red and smooth color profiles reported. Based on the model, our analysis suggests two populations of field elliptical galaxies, one formed recently, within Շ1 Gyr, and another much older, formed տ4 Gyr since the redshift of observation.

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Section: Isupporting

confidence: 91%

The Origin of Blue Cores in Hubble Deep Field E/S0 Galaxies

Menanteau

Jiménez

Matteuccí

2001

The Astrophysical Journal

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“…We integrate the disk/ bulge model in circular annuli to the radius that contains half of the light, setting the average effective surface brightness SB e equal to L total =2 r 2 h . The local samples for earlytype galaxies come from Jørgensen, Franx, & Kjoergaard (1996), Faber et al (1989), and Bernardi et al (2003). These samples use circular or geometric mean apertures.…”

Section: Photometric Propertiesmentioning

confidence: 99%

“…Section 5 considers the disk-dominated galaxies as well. Faber et al (1989), Jørgensen et al (1996), and Bernardi et al (2003) provide the local calibration for the FP. The Faber et al sample is measured in the B band, Jørgensen et al use the Gunn r band, and Bernardi et al use the Sloan Gunn filters (g Ã ; r Ã ; i Ã ; z Ã ).…”

Section: Aperture Correctionmentioning

confidence: 99%

“…The -values are aperture corrected. We use the fit of Bernardi et al (2003) to measure the magnitude offset from the high-z sample.…”

Section: Aperture Correctionmentioning

confidence: 99%

“…Both samples provide a similar FP relation, with logðR e Þ % 1:25 log þ 0:32SB e À 9:062, where we have minimized the residuals in the orthogonal direction. Bernardi et al (2003) also measure a tight FP relation from their 8000 galaxies. Their slope is higher than the one used here (1.49 compared to 1.25).…”

Section: No 1 2003mentioning

confidence: 99%

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The DEEP Groth Strip Survey. IX. Evolution of the Fundamental Plane of Field Galaxies

Gebhardt

Faber

Koo

et al. 2003

ApJ

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165

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Fundamental plane studies provide an excellent means of understanding the evolutionary history of earlytype galaxies. Using the Low Resolution Imaging Spectrograph on the Keck Telescope, we obtained internal stellar kinematic information for 36 field galaxies in the Groth Strip, 21 early-type and 15 disk galaxies. Their redshifts range from 0.3 to 1.0, with a median redshift of 0.8. The slope of the relation shows no difference compared with the local slope. However, there is significant evolution in the zero-point offset; an offset due to evolution in magnitude requires a 2.4 mag luminosity brightening at z ¼ 1. We see little differences of the offset with bulge fraction, which is a good surrogate for galaxy type. Correcting for the luminosity evolution reduces the orthogonal scatter in the fundamental plane to 8%, consistent with the local scatter. This scatter is measured for our sample and does not include results from other studies, which may have different selection effects. The difference in the degree of evolution between our field sample and published cluster galaxies suggests a more recent formation epoch, around z ¼ 1:5 for field galaxies compared to z > 2:0 for cluster galaxies. The magnitude difference implies that the field early-type galaxies are about 2 Gyr younger than the cluster ellipticals using standard single-burst models. However, the same models imply a significant change in the rest-frame UÀB color from then to the present, which is not seen in our sample. Continuous low-level star formation, however, would serve to explain the constant colors over this large magnitude change. A consistent model has 7% of the stellar mass created after the initial burst, using an exponentially decaying star formation rate with an e-folding time of 5 Gyr.

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Evolution and Environment of Early-Type Galaxies

Bernardi

Multiwavelength Mapping of Galaxy Formation and Evolution

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We study the photometric and spectral properties of 39320 early-type galaxies within the Sloan Digital Sky Survey (SDSS), as a function of both local environment and redshift. The distance to the nearest cluster of galaxies (scaled by the virial radius of the cluster) and the distance to the 10 th nearest luminous neighbor (M r < −21.5) were used to define two extremes in environment. The properties of early-type galaxies are weakly but significantly different in these two extremes. In particular, the Fundamental Plane of early-type galaxies in the lowest density environment is systematically brighter in surface brightness (by ∼ 0.08 mag/arcsec 2 in r) compared to the high density environment. A similar brightening is seen in the SDSS g and i photometric passbands. Although the Fundamental Plane is slightly thicker in the bluer passbands, we do not find any significant correlation between the thickness and the environment.Chemical abundance indicators are studied using composite spectra, which we provide in tabular form. Tables of line strengths measured from these spectra, and parameters derived from these line strengths are also provided. From these we find that, at fixed luminosity, early-type galaxies in low density environments are slightly bluer, with stronger OII emission and stronger Hδ and Hγ Balmer absorption lines, indicative of star-formation in the not very distant past. These galaxies also tend to have systematically weaker D4000 indices. The Lick indices and α-element abundance indicators correlate weakly but significantly with environment. For example, at fixed velocity dispersion, Mg is weaker in early-type galaxies in low density environments by 30% of the rms scatter across the full sample, whereas most Fe indicators show no significant environmental dependence.The galaxies in our sample span a redshift range which corresponds to lookback times of ∼1 Gyr. We see clear evidence for evolution of line-index strengths over this time.Since the low redshift population is almost certainly a passively aged version of the more distant population, age is likely the main driver for any observed evolution. We use the observed redshift evolution as a model independent clock to identify indicators which are more sensitive to age than to other effects such as metallicity. In principle, for a passively -2evolving population, comparison of the trends with redshift and environment constrain how strongly the luminosity-weighted ages and metallicities depend on environment. We develop a method for doing this which does not depend upon the details of stellar population synthesis models. Our analysis suggests that the galaxies which populate the densest regions in our sample are older by ∼ 1 Gyrs than objects of the same luminosity in the least dense regions, and that metallicity differences are negligible.We also use single burst stellar population synthesis models, which allow for nonsolar α-element abundance ratios, to interpret our data. The combination Hβ, Mgb and Fe suggests that age, metallicity and α-enhance...

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Cluster versus Field Elliptical Galaxies and Clues on Their Formation

Cited by 150 publications

References 34 publications

The Origin of Blue Cores in Hubble Deep Field E/S0 Galaxies

The Origin of Blue Cores in Hubble Deep Field E/S0 Galaxies

The DEEP Groth Strip Survey. IX. Evolution of the Fundamental Plane of Field Galaxies

Evolution and Environment of Early-Type Galaxies

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