scholarly journals What does strong gravitational lensing? The mass and redshift distribution of high-magnification lenses

2020 ◽  
Vol 495 (4) ◽  
pp. 3727-3739 ◽  
Author(s):  
Andrew Robertson ◽  
Graham P Smith ◽  
Richard Massey ◽  
Vincent Eke ◽  
Mathilde Jauzac ◽  
...  
Keyword(s):  
Gravitational Lensing ◽  
Point Sources ◽  
High Magnification ◽  
Lower Mass ◽  
Redshift Distribution ◽  
Density Profiles ◽  
Massive Galaxies ◽  
Strong Gravitational Lensing ◽  
Hydrodynamical Simulations ◽  
Halo Masses

ABSTRACT Many distant objects can only be detected, or become more scientifically valuable, if they have been highly magnified by strong gravitational lensing. We use eagle and bahamas, two recent cosmological hydrodynamical simulations, to predict the probability distribution for both the lens mass and lens redshift when point sources are highly magnified by gravitational lensing. For sources at a redshift of 2, we find the distribution of lens redshifts to be broad, peaking at z ≈ 0.6. The contribution of different lens masses is also fairly broad, with most high-magnification lensing due to lenses with halo masses between 1012 and $10^{14} \mathrm{\, M_\odot }$. Lower mass haloes are inefficient lenses, while more massive haloes are rare. We find that a simple model in which all haloes have singular isothermal sphere density profiles can approximately reproduce the simulation predictions, although such a model overpredicts the importance of haloes with mass $\lt 10^{12} \mathrm{\, M_\odot }$ for lensing. We also calculate the probability that point sources at different redshifts are strongly lensed. At low redshift, high magnifications are extremely unlikely. Each z = 0.5 source produces, on average, 5 × 10−7 images with magnification greater than 10; for z = 2, this increases to about 2 × 10−5. Our results imply that searches for strongly lensed optical transients, including the optical counterparts to strongly lensed gravitational waves, can be optimized by monitoring massive galaxies, groups, and clusters rather than concentrating on an individual population of lenses.

scholarly journals The nature of submillimetre and highly star-forming galaxies in the EAGLE simulation

2019 ◽  
Vol 488 (2) ◽  
pp. 2440-2454 ◽  
Author(s):  
Stuart McAlpine ◽  
Ian Smail ◽  
Richard G Bower ◽  
A M Swinbank ◽  
James W Trayford ◽  
...  
Keyword(s):  
Reasonable Agreement ◽  
Lower Mass ◽  
Redshift Distribution ◽  
Gas Reservoir ◽  
Massive Galaxies ◽  
Star Forming ◽  
Hydrodynamical Simulation ◽  
Galaxy Population ◽  
Gas Fractions ◽  
Selection Of

ABSTRACT We exploit EAGLE, a cosmological hydrodynamical simulation, to reproduce the selection of the observed submillimetre (submm) galaxy population by selecting the model galaxies at z ≥ 1 with mock submm fluxes $S_{850\, \mu \mathrm{m}}$ ≥ 1 mJy. We find a reasonable agreement between the model galaxies within this sample and the properties of the observed submm population, such as their star formation rates (SFRs) at z < 3, redshift distribution, and many integrated galaxy properties. We find that the median redshift of the $S_{850\, \mu \mathrm{m}}$ ≥ 1 mJy model population is z ≈ 2.5, and that they are massive galaxies (M* ∼ 1011 M⊙) with high dust masses (Mdust ∼ 108 M⊙), gas fractions (fgas ≈ 50 per cent), and SFRs ($\dot{M}_* \approx 100$ M⊙ yr−1). In addition, we find that they have major and minor merger fractions similar to the general population, suggesting that mergers are not the sole driver of the high SFRs in the model submm galaxies. Instead, the $S_{850\, \mu \mathrm{m}}$ ≥ 1 mJy model galaxies yield high SFRs primarily because they maintain a significant gas reservoir as a result of hosting an undermassive black hole relative to comparably massive galaxies. Not all ‘highly star-forming’ ($\dot{M}_* \ge 80$ M⊙ yr−1) eagle galaxies have submm fluxes $S_{850\, \mu \mathrm{m}}$ ≥ 1 mJy. We investigate the nature of these highly star-forming ‘Submm-Faint’ galaxies (i.e. $\dot{M}_* \ge 80$ M⊙ yr−1 but $S_{850\, \mu \mathrm{m}}$ < 1 mJy) and find that they are similar to the model submm galaxies, being gas rich and hosting undermassive black holes. However, they are also typically at higher redshifts (z > 4) and are lower mass (M* ∼ 1010 M⊙). These typically higher redshift galaxies show stronger evidence for having been triggered by major mergers, and critically, they are likely missed by most current submm surveys due to their higher dust temperatures and lower dust masses.

scholarly journals Quantized Redshifts - New Physics or Old Muddle?

1999 ◽  
Vol 194 ◽  
pp. 290-294
Author(s):  
W.M. Napier
Keyword(s):  
Energy Density ◽  
Gravitational Lensing ◽  
Confidence Level ◽  
Spiral Galaxies ◽  
New Physics ◽  
Frame Of Reference ◽  
High Confidence ◽  
Redshift Distribution ◽  
Massive Galaxies ◽  
High Confidence Level

The HI redshift distribution of nearby spiral galaxies has been studied to test long-running but generally ignored claims that extragalactic redshifts are periodic or ‘quantized’. The existence of the phenomenon is confirmed at an extremely high confidence level, the quantization appearing in the galactocentric frame of reference. It is proposed that the energy density of the vacuum is a local, oscillating quantity associated with large masses such as spiral galaxies. A variety of ‘anomalies’ should then be detectable in massive galaxies, associated with their redshifts, their ambient gravitational lensing and their dynamics.

scholarly journals High accuracy analytical solutions for the projected mass (counts) & surface density (brightness) of Einasto profiles

2021 ◽  
Author(s):  
Barun K Dhar
Keyword(s):  
Dark Matter ◽  
Gravitational Lensing ◽  
Surface Density ◽  
Surface Brightness ◽  
Analytical Approximation ◽  
High Accuracy ◽  
Density Profiles ◽  
Massive Galaxies ◽  
Multiple Components ◽  
Number Counts

Abstract The Einasto profile has been successful in describing the density profiles of dark matter haloes in ΛCDM N-body simulations. It has also been able to describe multiple components in the surface brightness profiles of galaxies. However, analytically projecting it to calculate quantities under projection is challenging. In this paper, we will see the development of a highly accurate analytical approximation for the mass (or counts) enclosed in an infinitely long cylindrical column for Einasto profiles—also known as the projected mass (or counts)—using a novel methodology. We will then develop a self-consistent high accuracy model for the surface density from the expression for the projected mass. Both models are quite accurate for a broad family of functions, with a shape parameter α varying by a factor of 100 in the range 0.05 ≲ α ≲ 5.0, with fractional errors ∼10−6 for α ≲ 0.4. Profiles with α ≲ 0.4 have been shown to fit the density profiles of dark matter haloes in N-body simulations as well as the luminosity profiles of the outer components of massive galaxies. Since the projected mass and the surface density are used in gravitational lensing, I will illustrate how these models facilitate (for the first time) analytical computation of several quantities of interest in lensing due to Einasto profiles. The models, however, are not limited to lensing and apply to similar quantities under projection, such as the projected luminosity, the projected (columnar) number counts and the projected density or the surface brightness.

scholarly journals QSO Strong Gravitational Lensing and the Detection of Dark Halos

2007 ◽  
Vol 3 (S244) ◽  
pp. 186-195
Author(s):  
Andrea V. Macciò
Keyword(s):  
Dark Matter ◽  
Galaxy Formation ◽  
Gravitational Lensing ◽  
Massive Particle ◽  
Flux Ratio ◽  
Dark Matter Halo ◽  
Microwave Background ◽  
Strong Gravitational Lensing ◽  
Hydrodynamical Simulations ◽  
Good Agreement

AbstractWe present recent results concerning the possibility to detect dark satellites around galaxies using QSO strong gravitational lensing. Combining high resolution hydrodynamical simulations of galaxy formation and analytic studies we show that current QSO observations data do not present any evidence for the existence of such satellites. The amount of substructures predicted by CDM within a galaxy size dark matter halo is too low to explain the observed anomalies in the QSO images flux ratio.Nevertheless the fluxes of QSO multiple images can be used to constrain the CDM power spectrum on small scales and test different dark matter candidates. We show that a warm dark matter scenario, with an insufficiently massive particle, fails to reproduce the observational data. Our results suggest a lower limit of few keV (~ 10) for the mass of warm dark matter candidates in the form of a sterile neutrino, in good agreement with previous results coming from Lyman-α forest and Cosmic Microwave Background analysis.

scholarly journals Using strong gravitational lensing to probe the post-reionization H i power spectrum

2020 ◽  
Vol 498 (3) ◽  
pp. 3275-3282
Author(s):  
Urvashi Arora ◽  
Prasun Dutta
Keyword(s):  
Power Spectrum ◽  
Gravitational Lensing ◽  
Neutral Hydrogen ◽  
Point Sources ◽  
Dark Matter Halo ◽  
Strong Gravitational Lensing ◽  
The Galaxy ◽  
Formation And Evolution ◽  
The Universe ◽  
Expected Signal

ABSTRACT Probing statistical distribution of the neutral hydrogen (H i) using the redshifted 21-cm hyperfine-transition spectral line holds the key to understand the formation and evolution of the matter density in the Universe. The two-point statistics of the H i distribution can be estimated by measuring the power spectrum of the redshifted 21-cm signal using visibility correlation. A major challenge in this regard is that the expected signal is weak compared to the foreground contribution from the Galactic synchrotron emission and extragalactic point sources in the observing frequencies. In this work, we investigate the possibility of detecting the power spectrum of the redshifted 21-cm signal by using strong gravitational lensing of the galaxy clusters. This method has the advantage that it only enhances the H i signal and not the diffuse Galactic foreground. Based on four simple models of the cluster potentials, we show that the strong lenses at relatively lower redshifts with more than one dark matter halo significantly enhance the 21-cm signal from the post-reionization era. We discuss the merits and demerits of the method and the future studies required for further investigations.

scholarly journals PROBING THE INNER KILOPARSEC OF MASSIVE GALAXIES WITH STRONG GRAVITATIONAL LENSING

2015 ◽  
Vol 799 (2) ◽  
pp. L22 ◽  
Author(s):  
Yashar D. Hezaveh ◽  
Philip J. Marshall ◽  
Roger D. Blandford
Keyword(s):  
Gravitational Lensing ◽  
Massive Galaxies ◽  
Strong Gravitational Lensing

scholarly journals An ALMA survey of the SCUBA-2 Cosmology Legacy Survey UKIDSS/UDS field: Halo Masses for Submillimetre Galaxies

2021 ◽  
Author(s):  
S M Stach ◽  
I Smail ◽  
A Amvrosiadis ◽  
A M Swinbank ◽  
U Dudzevičiūtė ◽  
...  
Keyword(s):  
Spatial Clustering ◽  
Distribution Functions ◽  
Gas Reservoirs ◽  
Redshift Distribution ◽  
Massive Galaxies ◽  
Deep Survey ◽  
Gas Cooling ◽  
Cool Gas ◽  
Halo Masses ◽  
Full Probability

Abstract We present an analysis of the spatial clustering of a large sample of high-resolution, interferometically identified, submillimetre galaxies (SMGs). We measure the projected cross-correlation function of ∼ 350 SMGs in the UKIDSS Ultra Deep-Survey Field across a redshift range of z = 1.5–3 utilising a method that incorporates the uncertainties in the redshift measurements for both the SMGs and cross-correlated galaxies through sampling their full probability distribution functions. By measuring the absolute linear bias of the SMGs we derive halo masses of $\log _{10}(M_{\rm halo}[{h^{-1}\, \rm M_{\odot }}])$ ∼ 12.8 with no evidence of evolution in the halo masses with redshift, contrary to some previous work. From considering models of halo mass growth rates we predict that the SMGs will reside in haloes of mass $\log _{10}(M_{\rm halo}[{h^{-1}\, \rm M_{\odot }}])$ ∼ 13.2 at z = 0, consistent with the expectation that the majority of z = 1.5–3 SMGs will evolve into present-day spheroidal galaxies. Finally, comparing to models of stellar-to-halo mass ratios, we show that SMGs may correspond to systems that are maximally efficient at converting their gas reservoirs into stars. We compare them to a simple model for gas cooling in halos that suggests that the unique properties of the SMG population, including their high levels of star-formation and their redshift distribution, are a result of the SMGs being the most massive galaxies that are still able to accrete cool gas from their surrounding intragalactic medium.

scholarly journals Constraints on Galaxy Density Profiles from Strong Gravitational Lensing: The Case of B1933+503

2001 ◽  
Vol 554 (2) ◽  
pp. 1216-1226 ◽  
Author(s):  
J. D. Cohn ◽  
C. S. Kochanek ◽  
B. A. McLeod ◽  
C. R. Keeton
Keyword(s):  
Gravitational Lensing ◽  
Density Profiles ◽  
Strong Gravitational Lensing
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