scholarly journals Shape, Color, and Distance in Weak Gravitational Flexion

2020 ◽  
Author(s):  
Joseph M Fabritius ◽  
Evan J Arena ◽  
David M Goldberg
Keyword(s):  
Gravitational Lensing ◽  
Rotational Symmetry ◽  
High Redshift ◽  
Morphological Type ◽  
Elliptical Galaxies ◽  
Early Type ◽  
Late Type ◽  
Color Measurements ◽  
Redshift Galaxy ◽  
Intrinsic Scatter

Abstract Canonically, elliptical galaxies might be expected to have a perfect rotational symmetry, making them ideal targets for flexion studies - however, this assumption hasn’t been tested. We have undertaken an analysis of low and high redshift galaxy catalogs of known morphological type with a new gravitational lensing code, Lenser. Using color measurements in the u − r bands and fit Sérsic index values, objects with characteristics consistent with early-type galaxies are found to have a lower intrinsic scatter in flexion signal than late-type galaxies. We find this measured flexion noise can be reduced by more than a factor of two at both low and high redshift.

scholarly journals CONSTRAINING TEVES GRAVITY AS EFFECTIVE DARK MATTER AND DARK ENERGY

2007 ◽  
Vol 16 (12a) ◽  
pp. 2055-2063 ◽  
Author(s):  
HONGSHENG ZHAO
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Scalar Field ◽  
Gravitational Lensing ◽  
Cold Dark Matter ◽  
High Redshift ◽  
Elliptical Galaxies ◽  
Dual Roles ◽  
Acceleration Of The Universe ◽  
The Universe

The phenomena customarily described with the standard ΛCDM model are broadly reproduced by an extremely simple model in TeVeS, Bekenstein's1 modification of general relativity motivated by galaxy phenomenology. Our model can account for the acceleration of the Universe seen at SNeIa distances without a cosmological constant, and the accelerations seen in rotation curves of nearby spiral galaxies and gravitational lensing of high-redshift elliptical galaxies without cold dark matter. The model is consistent with BBN and the neutrino mass between 0.05 eV to 2 eV. The TeVeS scalar field is shown to play the effective dual roles of dark matter and dark energy, with the amplitudes of the effects controlled by a μ function of the scalar field, called the μ essence here. We also discuss outliers to the theory's predictions on multiimaged galaxy lenses and outliers on the subgalaxy scale.

scholarly journals Mass dependent Evolution of Field Early-Type Galaxies Since z=1

2009 ◽  
Vol 5 (S262) ◽  
pp. 335-336
Author(s):  
Alexander Fritz ◽  
Inger Jørgensen ◽  
Ricardo P. Schiavon
Keyword(s):  
High Redshift ◽  
Galaxy Cluster ◽  
Early Type ◽  
Data Set ◽  
Redshift Galaxy ◽  
Slope Change ◽  
Formation And Evolution ◽  
Distant Field ◽  
Mass Dependent ◽  
Homogeneous Data

AbstractWe present the Fundamental Plane (FP) of field early-type galaxies at 0.5 < z < 1.0. Our project is a continuation of our efforts to understand the formation and evolution of early-type galaxies in different environments. The target galaxies were selected from the comprehensive and homogeneous data set of the Gemini/HST Galaxy Cluster Project. The distant field early-type galaxies follow a steeper FP relation compared to the local FP. The change in the slope of the FP can be interpreted as a mass-dependent evolution. Similar results have been found for cluster early-type galaxies in high redshift galaxy clusters at 0.8 < z <1. Therefore, the slope change of the FP appears to be independent of the environment of the galaxies.

scholarly journals A distortion of very-high-redshift galaxy number counts by gravitational lensing

Nature ◽  
2011 ◽  
Vol 469 (7329) ◽  
pp. 181-184 ◽  
Author(s):  
J. Stuart B. Wyithe ◽  
Haojing Yan ◽  
Rogier A. Windhorst ◽  
Shude Mao
Keyword(s):  
Gravitational Lensing ◽  
High Redshift ◽  
Redshift Galaxy ◽  
Number Counts ◽  
Very High

scholarly journals Kinematic properties and dark matter fraction of Virgo dwarf early-type galaxies

2012 ◽  
Vol 10 (H16) ◽  
pp. 335-335
Author(s):  
E. Toloba ◽  
A. Boselli ◽  
R. Peletier ◽  
J. Gorgas
Keyword(s):  
Dark Matter ◽  
Galaxy Evolution ◽  
Dwarf Galaxies ◽  
Elliptical Galaxies ◽  
Virgo Cluster ◽  
Early Type ◽  
Late Type ◽  
Fundamental Plane ◽  
Ram Pressure ◽  
Kinematic Properties

AbstractWhat happens to dwarf galaxies as they enter the cluster potential well is one of the main unknowns in studies of galaxy evolution. Several evidence suggests that late-type galaxies enter the cluster and are transformed to dwarf early-type galaxies (dEs). We study the Virgo cluster to understand which mechanisms are involved in this transformation. We find that the dEs in the outer parts of Virgo have rotation curves with shapes and amplitudes similar to late-type galaxies of the same luminosity (Fig. 1). These dEs are rotationally supported, have disky isophotes, and younger ages than those dEs in the center of Virgo, which are pressure supported, often have boxy isophotes and are older (Fig. 1). Ram pressure stripping, thus, explains the properties of the dEs located in the outskirts of Virgo. However, the dEs in the central cluster regions, which have lost their angular momentum, must have suffered a more violent transformation. A combination of ram pressure stripping and harassment is not enough to remove the rotation and the spiral/disky structures of these galaxies. We find that on the the Faber-Jackson and the Fundamental Plane relations dEs deviate from the trends of massive elliptical galaxies towards the position of dark matter dominated systems such as the dwarf spheroidal satellites of the Milky Way and M31. Both, rotationally and pressure supported dEs, however, populate the same region in these diagrams. This indicates that dEs have a non-negligible dark matter fraction within their half light radius.

Evidence for Initial Mass Function Variation in Massive Early-Type Galaxies

2020 ◽  
Vol 58 (1) ◽  
pp. 577-615 ◽  
Author(s):  
Russell J. Smith
Keyword(s):  
Gravitational Lensing ◽  
High Redshift ◽  
Mass Function ◽  
Spectroscopic Studies ◽  
Initial Mass Function ◽  
Initial Mass ◽  
Early Type ◽  
Stellar Component ◽  
The Imf

The initial mass function (IMF), describing the distribution of birth masses of stars, plays a pivotal role in establishing the observable properties of galaxies. This article reviews the evidence for variation in the IMF of massive early-type galaxies (ETGs), especially from spectroscopic studies and from dynamical and gravitational lensing measurements over the past decade. The principal conclusions are as follows: ▪  The spectra of massive ETGs depart from the predictions of models with Milky Way–like IMFs in a way that is best reproduced by assuming a steeper (bottom-heavy) IMF below ∼1 M⊙. ▪  Lensing and dynamical models, assuming a constant mass-to-light ratio for the stellar component, infer heavy IMFs, superficially supporting the result from spectra. ▪  The spectroscopic signal exhibits a steep gradient, however, and may be confined to the innermost region with scales ≲2 kpc; such internal variation in the stellar mass-to-light ratio would invalidate a key assumption of most dynamics and lensing studies. ▪  For masses above the main sequence turnoff in ancient populations (≳1 M⊙), there is little evidence for a steeper IMF in massive ETGs or their high-redshift progenitors; rather, a slightly shallower slope is preferred in this regime from several different arguments. ▪  Steep internal gradients may be responsible for some of the apparent discrepancies between different methods and also point to the cause of the IMF variation being restricted to conditions specific to the in situ formation phase of ETG cores.

scholarly journals Evidence for a Morphological Evolution of Spiral Galaxies

2001 ◽  
Vol 204 ◽  
pp. 387-387
Author(s):  
Yvan Dutil ◽  
Jean-René Roy
Keyword(s):  
Detailed Analysis ◽  
Spiral Galaxies ◽  
Morphological Evolution ◽  
Theoretical Models ◽  
Morphological Type ◽  
Disk Galaxies ◽  
Early Type ◽  
Late Type ◽  
Barred Galaxies ◽  
Abundance Profile

A detailed analysis of the oxygen abundance profile has been carried out on a sample of spiral galaxies from which very good data was available. The early-type galaxies of our sample display gradients that are flatter, and overall levels of O/H abundances that are higher, than those of normal late-type galaxies. Early-type galaxies show an identical trend in the behavior of extrapolated central abundance versus morphological type to that shown by late-type galaxies with strong bars, even in the absence of a bar. On a diagram showing extrapolated central abundances versus morphological types, two clearly separated sequences appear: late-type barred galaxies and early-type (barred or unbarred) galaxies clearly fall on a sequence 0.5 dex in abundance below that of normal late-type galaxies. This behavior is consistent with theoretical models of morphological evolution of disk galaxies by the formation and dissolution of a bar over a period of a few 109 yr, where later type galaxies (Sd, Sc, SBc) evolve into earlier-type disk galaxies (Sb, Sa) through transitory SBc and SBb phases.

scholarly journals The Shape of the Luminosity Profiles of Bulges

1996 ◽  
Vol 157 ◽  
pp. 86-87 ◽  
Author(s):  
Y. Andredakis ◽  
R. Peletier ◽  
M. Balcells
Keyword(s):  
Density Distribution ◽  
Decomposition Method ◽  
Surface Brightness ◽  
A Priori ◽  
Morphological Type ◽  
Early Type ◽  
Late Type ◽  
Dimensional Decomposition ◽  
The Galaxy ◽  
Light Profiles

AbstractWe extract the bulge light profiles of a sample of early type spirals, using K-band photometry and a new 2-dimensional decomposition method that does not assume a priori any surface brightness laws. We find that the shape of the light profile shows a good correlation with the morphological type of the galaxy, in the sense that the profiles tend to fall off more steeply at large radii for the later types. This trend shows that the formation of or interaction with the disk has probably affected the density distribution of the bulge. The fact that the transition in shape is continuous might also imply that most of the bulges of late type spirals were not formed by different mechanisms than the ones of early types.

scholarly journals Dorado and its member galaxies

2020 ◽  
Vol 643 ◽  
pp. A176
Author(s):  
R. Rampazzo ◽  
S. Ciroi ◽  
P. Mazzei ◽  
F. Di Mille ◽  
E. Congiu ◽  
...  
Keyword(s):  
Star Formation ◽  
Spiral Galaxies ◽  
Star Formation Rate ◽  
Large Fraction ◽  
Formation Rate ◽  
Morphological Type ◽  
Gas Content ◽  
Early Type ◽  
Late Type ◽  
Star Formation Activity

Context. Dorado is a nearby, rich and clumpy galaxy group that extends for several degrees in the southern hemisphere. Although several studies have been dedicated to defining its members, their kinematics, and the hot and cold gas content, in particular H I, their present star formation activity remains unknown. Aims. For the first time, we map the Hα distribution as a possible indicator of the star formation activity of Dorado members, a large fraction of which show interaction and merging signatures independently of their morphological type. Methods. With the 2.5 m du Pont and the 1m Swope telescopes, we obtained narrow-band calibrated images of 14 galaxies that form the backbone of the group, mapping Hα+[N II] down to a few 10−17 erg cm−2 s−1 arcsec−2. We estimated the galaxy star formation rate from the Hα fluxes and corrected for Galaxy foreground extinction and [N II] contamination. Results. We detected Hα+[N II] emission in all galaxies. H II regions clearly emerge in late-type galaxies, while in early-type galaxies the Hα+[N II] emission is dominated by [N II], especially in the central regions. However, H II complexes are revealed in four early-type galaxies. Even in the compact group SGC 0414-5559, in the projected centre of Dorado, H II regions are found both throughout the late-type galaxies and in the very outskirts of early-type members. Considering the Dorado group as a whole, we notice that the Hα+[N II] equivalent width, a measure of the specific star formation, increases with morphological type from early- to late-type members, although it remains lower than that observed in similar surveys of spiral galaxies. The star formation rate of the spiral members is in the range of what is observed in similar galaxies surveys (James et al., 2004). However, in three spiral galaxies, NGC 1536, PGC 75125, and IC 2058, the star formation rate is well below the median for their morphological classes. Conversely, the star formation rate of some early-type members tends to be higher than the average derived from Hα+[N II] surveys of this morphological family. Conclusions. We detected Hα+[N II] in all the early-type galaxies observed and half of them show H II regions in well-shaped rings as well as in their outskirts. These findings suggest that early-type galaxies in this group are not dead galaxies: their star formation has not yet shut down. Mechanisms such as gas stripping and gas accretion through galaxy–galaxy interaction seem relevant in modifying star formation in this evolutionary phase of Dorado.

scholarly journals Resolving Star Formation on Subkiloparsec Scales in the High-redshift Galaxy SDP.11 Using Gravitational Lensing

2018 ◽  
Vol 867 (2) ◽  
pp. 140 ◽  
Author(s):  
C. Lamarche ◽  
A. Verma ◽  
A. Vishwas ◽  
G. J. Stacey ◽  
D. Brisbin ◽  
...  
Keyword(s):  
Star Formation ◽  
Gravitational Lensing ◽  
High Redshift ◽  
Redshift Galaxy

scholarly journals Gravitational Lensing by Elliptical Galaxies

2005 ◽  
Vol 201 ◽  
pp. 490-491
Author(s):  
Daniel J. Mortlock ◽  
Rachel L. Webster
Keyword(s):  
Cross Section ◽  
Gravitational Lensing ◽  
Velocity Dispersion ◽  
High Redshift ◽  
Elliptical Galaxies ◽  
Line Of Sight ◽  
Density Parameter ◽  
Core Radius ◽  
The Core ◽  
Weakly Dependent

The probability that high-redshift quasars are gravitationally-lensed by intervening galaxies increases rapidly with the cosmological constant, ΩΛ0 (whilst being only weakly dependent on the density parameter, Ωm0), and the low number of lenses observed implies that ΩΛ0 ≲ 0.7 (e.g. Kochanek 1996). One of many uncertainties has been the (small) core radii of elliptical galaxies, which, at least naively, reduce their lensing cross-section. However, if ellipticals are normalised relative to their observed line-of-sight velocity dispersion, σ||, then increasing the core radius must result in an increased mass normalisation (specified by the assymptotic velocity dispersion, σ∞).

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