scholarly journals Discovery of an unusually compact lensed Lyman-break galaxy from the Hyper Suprime-Cam Survey

2020 ◽  
Vol 494 (3) ◽  
pp. 3156-3165 ◽  
Author(s):  
Anton T Jaelani ◽  
Anupreeta More ◽  
Alessandro Sonnenfeld ◽  
Masamune Oguri ◽  
Cristian E Rusu ◽  
...  
Keyword(s):  
Velocity Dispersion ◽  
High Redshift ◽  
Mass Model ◽  
Sharp Drop ◽  
Stellar Velocity ◽  
Absorption Features ◽  
Early Type Galaxy ◽  
Einstein Radius ◽  
Good Agreement

ABSTRACT We report the serendipitous discovery of HSC J0904–0102, a quadruply lensed Lyman-break galaxy (LBG) in the Survey of Gravitationally-lensed Objects in Hyper Suprime-Cam Imaging (SuGOHI). Owing to its point-like appearance, the source was thought to be a lensed active galactic nucleus. We obtained follow-up spectroscopic data with the Gemini Multi-Object Spectrographs on the Gemini South Telescope, which confirmed this to be a lens system. The deflecting foreground galaxy is a typical early-type galaxy at a high redshift of $z_{\ell}=0.957$ with stellar velocity dispersion $\sigma_v=259\pm56$ km s−1. The lensed source is identified as an LBG at $z_{\rm s}=3.403$, based on the sharp drop bluewards of Lyα and other absorption features. A simple lens mass model for the system, assuming a singular isothermal ellipsoid, yields an Einstein radius of $\theta_{\rm Ein}=1.23$ arcsec and a total mass within the Einstein radius of $M_{\rm Ein}=(5.55\pm0.24)\times10^{11}\rm M_{\odot}$ corresponding to a velocity dispersion of $\sigma_{\rm SIE}=283\pm3$ km s−1, which is in good agreement with the value derived spectroscopically. The most isolated lensed LBG image has a magnification of $\sim 6.5$. In comparison with other lensed LBGs and typical $z\sim4$ LBG populations, HSC J0904–0102 is unusually compact, an outlier at $>2\sigma$ confidence. Together with a previously discovered SuGOHI lens, HSC J1152+0047, which is similarly compact, we believe that the HSC survey is extending LBG studies down to smaller galaxy sizes.

scholarly journals STRIDES: Spectroscopic and photometric characterization of the environment and effects of mass along the line of sight to the gravitational lenses DES J0408–5354 and WGD 2038–4008

2020 ◽  
Vol 498 (3) ◽  
pp. 3241-3274 ◽  
Author(s):  
E J Buckley-Geer ◽  
H Lin ◽  
C E Rusu ◽  
J Poh ◽  
A Palmese ◽  
...  
Keyword(s):  
Time Delay ◽  
Velocity Dispersion ◽  
Line Of Sight ◽  
Wide Field ◽  
Gravitational Lenses ◽  
Mass Model ◽  
Stellar Velocity ◽  
Unit Density ◽  
Shift Criterion

ABSTRACT In time-delay cosmography, three of the key ingredients are (1) determining the velocity dispersion of the lensing galaxy, (2) identifying galaxies and groups along the line of sight with sufficient proximity and mass to be included in the mass model, and (3) estimating the external convergence κext from less massive structures that are not included in the mass model. We present results on all three of these ingredients for two time-delay lensed quad quasar systems, DES J0408–5354 and WGD 2038–4008 . We use the Gemini, Magellan, and VLT telescopes to obtain spectra to both measure the stellar velocity dispersions of the main lensing galaxies and to identify the line-of-sight galaxies in these systems. Next, we identify 10 groups in DES J0408–5354 and two groups in WGD 2038–4008 using a group-finding algorithm. We then identify the most significant galaxy and galaxy-group perturbers using the ‘flexion shift’ criterion. We determine the probability distribution function of the external convergence κext for both of these systems based on our spectroscopy and on the DES-only multiband wide-field observations. Using weighted galaxy counts, calibrated based on the Millennium Simulation, we find that DES J0408–5354 is located in a significantly underdense environment, leading to a tight (width $\sim 3{{\ \rm per\ cent}}$), negative-value κext distribution. On the other hand, WGD 2038–4008 is located in an environment of close to unit density, and its low source redshift results in a much tighter κext of $\sim 1{{\ \rm per\ cent}}$, as long as no external shear constraints are imposed.

scholarly journals Gas and Stellar Kinematics in NGC 6240

2001 ◽  
Vol 205 ◽  
pp. 220-221
Author(s):  
Matthias Tecza ◽  
Linda Tacconi ◽  
Reinhard Genzel
Keyword(s):  
Near Infrared ◽  
Velocity Dispersion ◽  
Rotating Disk ◽  
Stellar Kinematics ◽  
Rapid Rotation ◽  
Integral Field Spectroscopy ◽  
Stellar Velocity ◽  
Nir Emission ◽  
Absorption Features ◽  
Integral Field

We present results from sub-arcsecond near infrared integral field spectroscopy and millimeter IRAM-interferometry of the interacting galaxy NGC 6240. Using stellar absorption features in the NIR we determined the stellar velocity field and dispersion in NGC 6240. The two NIR emission peaks show rapid rotation and indicate a prograde encounter of the two progenitor galaxies. From the velocity dispersion an excess mass between the two nuclei is detected. This mass can be attributed to a massive rotating disk of cold CO gas located between the nuclei.

scholarly journals Massive Black Holes in Galactic Halos?

1987 ◽  
Vol 117 ◽  
pp. 412-412
Author(s):  
C. G. Lacey ◽  
J. P. Ostriker
Keyword(s):  
Black Holes ◽  
Power Law ◽  
Velocity Dispersion ◽  
Solar Neighbourhood ◽  
Galactic Halos ◽  
Massive Black Holes ◽  
Galaxy Halos ◽  
Stellar Velocity ◽  
The Many ◽  
Good Agreement

We consider the idea that galaxy halos are composed of massive black holes, as a possible resolution of two problems: the composition of dark halos, and the heating of stellar disks. Scattering of disk stars by halo black holes with mass MH, velocity dispersion σH and number density nH causes the stellar velocity dispersion to increase with time t as σ≈(Dt)1/2 for t large, where D α nHM2H in Λ/σH, and in Λ is the Coulomb logarithm. This time-dependence is in good agreement with observations, as is the prediction for the axial ratios of the velocity ellipsoid σu: σv: σw. To account for the magnitude of the disk velocity dispersion in the solar neighbourhood, we require MH≈2 × 106M⊙. The stellar distribution function is predicted to be approximately isothermal at low epicyclic energies, in the Fokker-Planck regime in which the effect of the many distant, weak encounters dominates, but with a power-law tail at high energies produced by the relatively rare close encounters. This tail has the form N(E)αE−2, where E is the horizontal or vertical epicyclic energy, and N(E) is the number of stars per unit area of the disk, per unit E. The fraction of stars in this power-law tail depends only on the value of in Λ, and is about 1% for typical values. This provides a possible explanation for the high velocity A stars found in the solar neighbourhood. This disk heating mechanism can also account for the approximate constancy of the disk scaleheight with radius that is observed in other spiral galaxies, although this does not result as naturally as the other properties.

scholarly journals Velocity dispersion of brightest cluster galaxies in cosmological simulations

2021 ◽  
Vol 507 (4) ◽  
pp. 5780-5795
Author(s):  
I Marini ◽  
S Borgani ◽  
A Saro ◽  
G L Granato ◽  
C Ragone-Figueroa ◽  
...  
Keyword(s):  
Dark Matter ◽  
Velocity Dispersion ◽  
Stellar Envelope ◽  
Cluster Galaxies ◽  
Massive Galaxies ◽  
Brightest Cluster Galaxies ◽  
Stellar Velocity ◽  
Intracluster Light ◽  
The Universe ◽  
Good Agreement

ABSTRACT Using the DIANOGA hydrodynamical zoom-in simulation set of galaxy clusters, we analyse the dynamics traced by stars belonging to the brightest cluster galaxies (BCGs) and their surrounding diffuse component, forming the intracluster light (ICL), and compare it to the dynamics traced by dark matter and galaxies identified in the simulations. We compute scaling relations between the BCG and cluster velocity dispersions and their corresponding masses (i.e. $M_\mathrm{BCG}^{\star }$–$\sigma _\mathrm{BCG}^{\star }$, M200–σ200, $M_\mathrm{BCG}^{\star }$–M200, and $\sigma _\mathrm{BCG}^{\star }$–σ200), we find in general a good agreement with observational results. Our simulations also predict $\sigma _\mathrm{BCG}^{\star }$–σ200 relation to not change significantly up to redshift z = 1, in line with a relatively slow accretion of the BCG stellar mass at late times. We analyse the main features of the velocity dispersion profiles, as traced by stars, dark matter, and galaxies. As a result, we discuss that observed stellar velocity dispersion profiles in the inner cluster regions are in excellent agreement with simulations. We also report that the slopes of the BCG velocity dispersion profile from simulations agree with what is measured in observations, confirming the existence of a robust correlation between the stellar velocity dispersion slope and the cluster velocity dispersion (thus, cluster mass) when the former is computed within 0.1R500. Our results demonstrate that simulations can correctly describe the dynamics of BCGs and their surrounding stellar envelope, as determined by the past star formation and assembly histories of the most massive galaxies of the Universe.

scholarly journals Dynamical masses of early-type galaxies at z ~ 2

2012 ◽  
Vol 8 (S295) ◽  
pp. 37-44
Author(s):  
Michele Cappellari
Keyword(s):  
Galaxy Formation ◽  
Velocity Dispersion ◽  
High Redshift ◽  
Early Type ◽  
Imaging Data ◽  
Galaxy Dynamics ◽  
Stellar Velocity ◽  
Multi Band ◽  
The Imf

AbstractThe evolution of masses and sizes of passive (early-type) galaxies with redshift provides ideal constraints to galaxy formation models. These parameters can in principle be obtained for large galaxy samples from multi-band photometry alone. However the accuracy of photometric masses is limited by the non-universality of the IMF. Galaxy sizes can be biased at high redshift due to the inferior quality of the imaging data. Both problems can be avoided using galaxy dynamics, and in particular by measuring the galaxies stellar velocity dispersion. Here we provide an overview of the efforts in this direction.

scholarly journals Spectroscopic confirmation and modelling of two lensed quadruple quasars in the Dark Energy Survey public footprint

2019 ◽  
Vol 485 (4) ◽  
pp. 5086-5095
Author(s):  
C Spiniello ◽  
A V Sergeyev ◽  
L Marchetti ◽  
C Tortora ◽  
N R Napolitano ◽  
...  
Keyword(s):  
Dark Energy ◽  
Velocity Dispersion ◽  
Gravitational Lenses ◽  
Intrinsic Variability ◽  
Apparent Brightness ◽  
Dark Energy Survey ◽  
Stellar Velocity ◽  
Energy Survey

ABSTRACT Quadruply lensed quasars are extremely rare objects, but incredibly powerful cosmological tools. Only few dozen are known in the whole sky. Here we present the spectroscopic confirmation of two new quadruplets WG0214-2105 and WG2100-4452 discovered by Agnello & Spiniello (2018) within the Dark Energy Survey public footprints. We have conducted spectroscopic follow-up of these systems with the Southern African Large Telescope as part of a program that aims at confirming the largest possible number of strong gravitational lenses in the equatorial and Southern hemisphere. For both systems, we present the sources spectra that allowed us to estimate their redshifts and unambiguously confirm their lensing nature. For the brighter deflector (WG2100-4452) we measure the spectroscopic redshift and the stellar velocity dispersion from optical absorption lines in the spectrum. For the other system we infer the lens redshift from photometry, being the quality of the spectra not good enough. We obtain photometry for both lenses, directly from multiband images, isolating the lenses from the quasars. One of the quadruplets, WG0214-2105, was also observed by Pan-STARRS, allowing us to estimate the apparent brightness of each quasar image at two different epochs, and thus to find evidence for flux variability. This result could suggest a microlensing event for the faintest components, although intrinsic variability cannot be excluded with only two epochs. Finally, we present simple lens models for both quadruplets, obtaining Einstein radii, singular isothermal ellipsoid velocity dispersions, ellipticities, and position angles of the lenses, as well as time-delay predictions assuming a concordance cosmological model.

Simulated synchrotron emission for the Tycho’s supernova remnants: an asymmetric initial mass model

2020 ◽  
Vol 494 (2) ◽  
pp. 1531-1538
Author(s):  
A Moranchel-Basurto ◽  
P F Velázquez ◽  
G Ares de Parga ◽  
E M Reynoso ◽  
E M Schneiter ◽  
...  
Keyword(s):  
Supernova Remnants ◽  
Brightness Distribution ◽  
Radio Continuum ◽  
Initial Mass ◽  
Continuum Emission ◽  
Synchrotron Emission ◽  
Mass Model ◽  
Mhd Simulations ◽  
Tycho’S Snr ◽  
Good Agreement

ABSTRACT We have performed 3D magnetohydrodynamics (MHD) numerical simulations with the aim of exploring the scenario in which the initial mass distribution of a supernova (SN) explosion is anisotropic. The purpose is to analyse if this scenario can also explain the radio-continuum emission and the expansion observed in young supernova remnants (SNRs). To study the expansion, synthetic polarized synchrotron emission maps were computed from the MHD simulations. We found a good agreement (under a number of assumptions) between this expansion study and previous observational results applied to Tycho’s SNR, which represents a good example of asymmetric young SNRs. Additionally, both the observed morphology and the brightness distribution are qualitatively reproduced.

scholarly journals Survey of Gravitationally Lensed Objects in HSC Imaging (SuGOHI) – VII. Discovery and confirmation of three strongly lensed quasars†

2021 ◽  
Vol 502 (1) ◽  
pp. 1487-1493
Author(s):  
Anton T Jaelani ◽  
Cristian E Rusu ◽  
Issha Kayo ◽  
Anupreeta More ◽  
Alessandro Sonnenfeld ◽  
...  
Keyword(s):  
Spectroscopic Data ◽  
Point Sources ◽  
Sloan Digital Sky Survey ◽  
Early Type ◽  
Blue Point ◽  
X Ray ◽  
Quasar Spectra ◽  
Strategic Program ◽  
Early Type Galaxy

ABSTRACT We present spectroscopic confirmation of three new two-image gravitationally lensed quasars, compiled from existing strong lens and X-ray catalogues. Images of HSC J091843.27–022007.5 show a red galaxy with two blue point sources at either side, separated by 2.26 arcsec. This system has a source and a lens redshifts zs = 0.804 and zℓ = 0.459, respectively, as obtained by our follow-up spectroscopic data. CXCO J100201.50+020330.0 shows two point sources separated by 0.85 arcsec on either side of an early-type galaxy. The follow-up spectroscopic data confirm the fainter quasar has the same redshift with the brighter quasar from the Sloan Digital Sky Survey (SDSS) fiber spectrum at zs = 2.016. The deflecting foreground galaxy is a typical early-type galaxy at a redshift of zℓ = 0.439. SDSS J135944.21+012809.8 has two point sources with quasar spectra at the same redshift zs = 1.096, separated by 1.05 arcsec, and fits to the HSC images confirm the presence of a galaxy between these. These discoveries demonstrate the power of the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP)’s deep imaging and wide sky coverage. Combined with existing X-ray source catalogues and follow-up spectroscopy, the HSC-SSP provides us unique opportunities to find multiple-image quasars lensed by a foreground galaxy.

Emission of molecular nitrogen at tight focusing of femtosecond laser pulses in air

2021 ◽  
pp. 42-48
Author(s):  
A.A. Ilyin ◽  
◽  
K.A. Shmirko ◽  
S.S. Golik ◽  
D.Yu. Proschenko ◽  
...  
Keyword(s):  
Particle Density ◽  
Molecular Nitrogen ◽  
Laser Pulses ◽  
Femtosecond Laser Pulses ◽  
Plasma Particle ◽  
Sharp Drop ◽  
Radiation Level ◽  
Femtosecond Radiation ◽  
Tight Focusing ◽  
Good Agreement

A numerical model describing the dynamics of plasma particle density upon filamentation of femtosecond radiation in the air is presented. The simulation results are in good agreement with the experimental data. The pumping processes of the N2 and N2+ radiative levels are investigated. The model predicts a sharp drop in electron temperature and density within 1 ns. For the first positive nitrogen system, an excess of the population of the upper radiation level over the population of the lower one is observed for 550 ps.

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