Constraints on Elliptical Galaxy Formation from Dry Mergers

2006 ◽  
Vol 2 (S235) ◽  
pp. 195-195
Author(s):  
Julia M. Comerford ◽  
Eliot Quataert ◽  
Chung-Pei Ma
Keyword(s):  
Galaxy Formation ◽  
Elliptical Galaxy ◽  
Elliptical Galaxies ◽  
Analytic Model ◽  
Dark Matter Halos ◽  
Early Type ◽  
Mass Assembly ◽  
Minor Mergers ◽  
Analytic Models

Recent observations suggest that dissipationless mergers of elliptical galaxies build up the population of massive early-type galaxies (Bell et al. 2004; Faber et al. 2006). This type of merger is observed in galaxy clusters (Tran et al. 2005) and predicted by semi-analytic models which find mass assembly times significantly later than star-formation times for the most massive elliptical galaxies (de Lucia & Blaizot 2006). Here, we use a semi-analytic model of minor mergers of dark matter halos to examine the role of dry minor mergers in elliptical galaxy formation.

scholarly journals Feedback and environmental effects in elliptical galaxies

2009 ◽  
Vol 5 (H15) ◽  
pp. 289-290
Author(s):  
Craig L. Sarazin
Keyword(s):  
Elliptical Galaxy ◽  
Elliptical Galaxies ◽  
Energy Output ◽  
Radio Sources ◽  
Early Type ◽  
Gas Stripping ◽  
Interstellar Gas ◽  
X Ray ◽  
Radio Jets

AbstractThe role of the environment of an elliptical galaxy on its hot interstellar gas is discussed. In general, the X-ray halos of early-type galaxies tend to be smaller and fainter in denser environments, with the exception of group-central galaxies. X-ray observations show many examples of nearby galaxies which are undergoing gas stripping. On the other hand, most bright galaxies in clusters do manage to retain small coronae of X-ray emission. Recent theoretical and observational results on the role of feedback from AGN at the centers of elliptical galaxies on their interstellar gas are reviewed. X-ray observations show many examples of X-ray holes in the central regions of brightest-cluster galaxies; in many cases, the X-ray holes are filled with radio lobes. Similar radio bubbles are seen in groups and individual early-type galaxies. “Ghost bubbles” are often seen at larger radii in clusters and galaxies; these bubbles are faint in high radio frequencies, and are believed to be old radio bubbles which have risen buoyantly in the hot gas. Low frequency radio observations show that many of the ghost bubbles have radio emission; in general, these long wavelength observations show that radio sources are much larger and involve greater energies than had been previously thought. The radio bubbles can be used to estimate the total energy output of the radio jets. The total energies deposited by radio jets exceed the losses from the gas due to radiative cooling, indicating that radio sources are energetically capable of heating the cooling core gas and preventing rapid cooling.

scholarly journals Using GAMA and H-ATLAS data to explore the cold dust properties of early-type galaxies

2011 ◽  
Vol 7 (S284) ◽  
pp. 262-264
Author(s):  
Nicola K. Agius ◽  
Anne E. Sansom ◽  
Cristina C. Popescu
Keyword(s):  
Galaxy Formation ◽  
Concentration Index ◽  
Elliptical Galaxies ◽  
Host Galaxy ◽  
Early Type ◽  
Large Dataset ◽  
Atlas Data ◽  
Multi Wavelength ◽  
Cold Dust

AbstractHierarchical galaxy formation models predict the development of elliptical galaxies through a combination of the mergers and interactions of smaller galaxies. We are carrying out a study of Early-Type Galaxies (ETGs) using GAMA multi-wavelength and Herschel-ATLAS sub-mm data to understand their intrinsic dust properties. The dust in some ETGs may be a relic of past interactions and mergers of galaxies, or may be produced within the galaxies themselves. With this large dataset we will probe the properties of the dust and its relation to host galaxy properties. This paper presents our criteria for selecting ETGs and explores the usefulness of proxies for their morphology, including optical colour, Sérsic index and Concentration index. We find that a combination of criteria including r band Concentration index, ellipticity and apparent sizes is needed to select a robust sample. Optical and sub-mm parameter diagnostics are examined for the selected ETG sample, and the sub-mm data are fitted with modified Planck functions giving initial estimates for the cold dust temperatures and masses.

Dual Stellar Halos in Early-type Galaxies and Formation of Massive Galaxies

2015 ◽  
Vol 11 (S317) ◽  
pp. 253-258
Author(s):  
Myung Gyoon Lee ◽  
In Sung Jang
Keyword(s):  
Strong Evidence ◽  
Elliptical Galaxy ◽  
Elliptical Galaxies ◽  
Early Type ◽  
Massive Galaxies ◽  
Mode Formation

AbstractM105 in the Leo I Group is a textbook example of a standard elliptical galaxy. It is only one of the few elliptical galaxies for which we can study their stellar halos using the resolved stars. It is an ideal target to study the structure and composition of stellar halos in elliptical galaxies. We present photometry and metallicity of the resolved stars in the inner and outer regions of M105. These provide strong evidence that there are two distinct stellar halos in this galaxy, a metal-poor (blue) halo and a metal-rich (red) halo. Then we compare them with those in other early-type galaxies and use the dual halo mode formation scenario to describe how massive galaxies formed.

scholarly journals A Model for the Sequence of Elliptical Galaxies

1987 ◽  
Vol 117 ◽  
pp. 367-367
Author(s):  
Rosemary F. G. Wyse ◽  
Bernard J. T. Jones
Keyword(s):  
Dark Matter ◽  
Power Spectrum ◽  
Galaxy Formation ◽  
Cold Dark Matter ◽  
Initial Conditions ◽  
Elliptical Galaxy ◽  
Elliptical Galaxies ◽  
Density Fluctuations ◽  
Analytic Approximation ◽  
Non Linear

We present a simple model for the formation of elliptical galaxies, based on a binary clustering hierarchy of dark matter, the chemical enrichment of the gas at each level being controlled by supernovae. The initial conditions for the non-linear phases of galaxy formation are set by the post-recombination power spectrum of density fluctuations. We investigate two models for this power spectrum - the first is a straightforward power law, |δk|2 ∝ kn, and the second is Peeble's analytic approximation to the emergent spectrum in a universe dominated by cold dark matter. The normalisation is chosen such that on some scale, say M ∼ 1012M⊙, the objects that condense out have properties - radius and velocity dispersion - resembling ‘typical’ galaxies. There is some ambiguity in this due to the poorly determined mass-to-light ratio of a typical elliptical galaxy — we look at two normalisations, σ1D ∼ 350kms−1 and σ1D ∼ 140kms−1. The choice determines which of Compton cooling or hydrogen cooling is more important during the galaxy formation period. The non-linear behaviour of the perturbations is treated by the homogeneous sphere approximation.

The Role of the Radial Orbit Instability in Dark Matter Halo Formation and Structure

2006 ◽  
Vol 2 (S235) ◽  
pp. 124-124
Author(s):  
J. M. Meyer ◽  
J. J. Dalcanton ◽  
T. R. Quinn ◽  
L. L. R. Williams ◽  
E. I. Barnes ◽  
...  
Keyword(s):  
Dark Matter ◽  
Density Profile ◽  
Dark Matter Halo ◽  
Dark Matter Halos ◽  
Radial Orbit ◽  
Profile Changes ◽  
Analytic Models ◽  
The Universe ◽  
Scale Length

AbstractFor nearly a decade, N-body simulations have revealed a nearly universal dark matter density profile. This density profile appears to be robust to changes in the overall density of the universe and the underlying power spectrum. Despite its universality, however, the physical origin of this profile has not yet been well understood. Semi-analytic models have suggested that scale lengths in dark matter halos may be determined by the onset of the radial orbit instability. We have tested this theory using N-body simulations of collapsing dark matter halos. The resulting halo structures are prolate in shape, due to the mild aspect of the instability. We find that the radial orbit instability sets a scale length at which the velocity dispersion changes rapidly from isotropic to radially anisotropic. Preliminary analysis suggests that this scale length is proportional to the radius at which the density profile changes shape, as is the case in the semi-analytic models; however, the coefficient of proportionality is different by a factor of ~2. We conclude that the radial orbit instability may be a key physical mechanism responsible for the nearly universal profiles of simulated dark matter halos.

scholarly journals Early-type galaxy formation: understanding the role of the environment

2014 ◽  
Vol 10 (S309) ◽  
pp. 291-292
Author(s):  
Ricardo Demarco ◽  
Alessandro Rettura ◽  
Chris Lidman ◽  
Julie Nantais ◽  
Yara Jaffe ◽  
...  
Keyword(s):  
Star Formation ◽  
Galaxy Evolution ◽  
Galaxy Formation ◽  
Early Type ◽  
Cluster Galaxy ◽  
Cluster Galaxies ◽  
Physical Mechanisms ◽  
Characteristic Features ◽  
Early Type Galaxy

AbstractOne of the most characteristic features of galaxy clusters is the so-called “red sequence” (RS) of early-type galaxies. Since these galaxies are, in general, devoid of gas and dust, their red colors are mainly a consequence of their passive nature. However, the physical mechanisms responsible for quenching their star formation, thus originating the RS, are poorly understood. Environmental effects should play a significant role in the formation of the RS by transforming the observed galaxy properties from late to early-type ones. In this respect, we have initiated a KMOS program aimed at studying the kinematical structure of cluster galaxies at 0.8 < z < 1.7 in an effort to disentangle the physical mechanisms responsible for cluster galaxy evolution and the formation of the RS.

Models for the Formation and Evolution of Spherical Galaxies

1974 ◽  
Vol 58 ◽  
pp. 191-194
Author(s):  
Richard B. Larson
Keyword(s):  
Star Formation ◽  
Galaxy Formation ◽  
Stellar Evolution ◽  
Elliptical Galaxy ◽  
Elliptical Galaxies ◽  
Dynamical Model ◽  
Model Calculations ◽  
Formation And Evolution

Detailed dynamical model calculations based on a conventional collapse picture of galaxy formation, and conventional assumptions concerning star formation and stellar evolution, are found to be able to reproduce satisfactorily the basic structural and photometric properties of elliptical galaxies. The quasar phenomenon may be identifiable with the formation of the nucleus of a giant elliptical galaxy.

scholarly journals Globular Clusters as Probes of the Formation History of Elliptical Galaxies: Results for NGC 4472

2002 ◽  
Vol 207 ◽  
pp. 333-335
Author(s):  
K.L. Rhode ◽  
S.E. Zepf
Keyword(s):  
Galaxy Formation ◽  
Globular Cluster ◽  
Globular Clusters ◽  
Spiral Galaxies ◽  
Elliptical Galaxy ◽  
Elliptical Galaxies ◽  
Cluster Systems ◽  
Large Sample ◽  
Formation History ◽  
History Of

We have undertaken a survey of the globular cluster systems of a large sample of elliptical and spiral galaxies in order to test predictions of elliptical galaxy formation models. Here we outline the survey and present a summary of our results for the Virgo elliptical NGC 4472.

scholarly journals Gas Accretion and Mergers in Massive Galaxies at z ~ 2

2012 ◽  
Vol 8 (S295) ◽  
pp. 45-48
Author(s):  
C. J. Conselice ◽  
Jamie Ownsworth ◽  
Alice Mortlock ◽  
Asa F. L. Bluck ◽  
Keyword(s):  
Galaxy Formation ◽  
Theoretical Models ◽  
Massive Galaxies ◽  
A Value ◽  
The Galaxy ◽  
Hydrodynamical Simulations ◽  
Minor Mergers ◽  
Galaxy Assembly ◽  
Gas Accretion

AbstractGalaxy assembly is an unsolved problem, with ΛCDM theoretical models unable to easily account for among other things, the abundances of massive galaxies, and the observed merger history. We show here how the problem of galaxy formation can be addressed in an empirical way without recourse to models. We discuss how galaxy assembly occurs at 1.5 < z < 3 examining the role of major and minor mergers, and gas accretion from the intergalactic medium in forming massive galaxies with log M* > 11 found within the GOODS NICMOS Survey (GNS). We find that major mergers, minor mergers and gas accretion are roughly equally important in the galaxy formation process during this epoch, with 64% of the mass assembled through merging and 36% through accreted gas which is later converted to stars, while 58% of all new star formation during this epoch arises from gas accretion. We also discuss how the total gas accretion rate is measured as Ṁ = 90±40 M⊙ yr−1 at this epoch, a value close to those found in some hydrodynamical simulations.

scholarly journals Elliptical Galaxies: Darkly Cloaked or Scantily Clad?

2004 ◽  
Vol 220 ◽  
pp. 165-170
Author(s):  
A. J. Romanowsky ◽  
N. G. Douglas ◽  
K. Kuijken ◽  
M. R. Merrifield ◽  
M. Arnaboldi ◽  
...  
Keyword(s):  
Galaxy Formation ◽  
Velocity Dispersion ◽  
Elliptical Galaxies ◽  
Small Sample ◽  
Early Type ◽  
Dynamical Models ◽  
Show Evidence ◽  
Major Merger ◽  
Nearby Galaxies ◽  
Ab Initio Models

Planetary nebulae (PNe) may be the most promising tracers in the halos of early-type galaxies. We have used multi-object spectrographs on the WHT and the VLT, and the new Planetary Nebula Spectrograph on the WHT, to obtain hundreds of PN velocities in a small sample of nearby galaxies. These ellipticals show weak halo rotation, which may be consistent with ab initio models of galaxy formation, but not with more detailed major merger simulations. the galaxies near L* show evidence of a universal declining velocity dispersion profile, and dynamical models indicate the presence of little dark matter within 5 Reff—implying halos either not as massive or not as centrally concentrated as CDM predicts.

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