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Zahid, H. Jabran,Geller, Margaret J.,Fabricant, Daniel G.,Hwang, Ho Seong American Astronomical Society 2016 The Astrophysical Journal Vol.832 No.2
<P>We examine the relation between stellar mass and central stellar velocity dispersion-the M*sigma relation-for massive quiescent galaxies at z < 0.7. We measure the local relation from the Sloan Digital Sky Survey and the intermediate redshift relation from the Smithsonian Hectospec Lensing Survey. Both samples are highly complete (>85%) and we consistently measure the stellar mass and velocity dispersion for the two samples. The M*sigma relation and its scatter are independent of redshift with sigma proportional to M*(0.3) for M* greater than or similar to 10(10.3) M-circle dot. The measured slope of the M*sigma relation is the same as the scaling between the total halo mass and the dark matter halo velocity dispersion obtained by N-body simulations. This consistency suggests that massive quiescent galaxies are virialized systems, where the central dark matter concentration is either a constant or negligible fraction of the stellar mass. The relation between the total galaxy mass (stellar + dark matter) and the central stellar velocity dispersion is consistent with the observed relation between the total mass of a galaxy cluster and the velocity dispersion of the cluster members. This result suggests that the central stellar velocity dispersion is directly proportional to the velocity dispersion of the dark matter halo. Thus, the central stellar velocity dispersion is a fundamental, directly observable property of galaxies, which may robustly connect galaxies to dark matter halos in N-body simulations. To interpret the results further in the context of Lambda CDM, it would be useful to analyze the relationship between the velocity dispersion of stellar particles and the velocity dispersion characterizing their dark matter halos in high-resolution cosmological hydrodynamic simulations.</P>
hCOSMOS: A Dense Spectroscopic Survey of <i>r</i> ≤ 21.3 Galaxies in the COSMOS field
Damjanov, Ivana,Zahid, H. Jabran,Geller, Margaret J.,Fabricant, Daniel G.,Hwang, Ho Seong American Astronomical Society 2018 The Astrophysical journal Supplement series Vol.234 No.2
<P>We describe the hCOSMOS redshift survey of the COSMOS field conducted with the Hectospec spectrograph on the MMT. In the central 1. deg(2), the hCOS20.6 subset of the survey is > 90% complete to a limiting magnitude r = 20.6. The hCOSMOS survey includes 1701 new redshifts in the COSMOS field. We also use the total of 4362 new and remeasured objects to derive the age-sensitive D(n)4000 index over the entire redshift interval 0.001 less than or similar to z less than or similar to 0.6. For 85% of the quiescent galaxies in hCOS20.6, we measure the central line-of-sight velocity dispersion. To explore potential uses of this survey, we combine previously measured galaxy sizes, profiles, and stellar masses with the spectroscopy. The comparison reveals the known relations among structural, kinematic, and stellar population properties. We also compare redshift and Dn4000 distributions of hCOS20.6 galaxies with SHELS; a complete spectroscopic survey of 4 deg(2) observed to the same depth. The redshift distributions in the two fields are very different, but the Dn4000 distribution is remarkably similar. The relation between velocity dispersion and stellar mass for massive hCOS20.6 galaxies is consistent with the local relation from the Sloan Digital Sky Survey. Using measured velocity dispersions, we test a photometric proxy calibrated to galaxies in the local universe. The systematic differences between the measured and photometric proxy velocity dispersions are correlated with galaxy dynamical and stellar population properties highlighting the importance of direct spectroscopic measurements.</P>
THE STELLAR MASS FUNDAMENTAL PLANE AND COMPACT QUIESCENT GALAXIES AT<i>z</i>< 0.6
Zahid, H. Jabran,Damjanov, Ivana,Geller, Margaret J.,Hwang, Ho Seong,Fabricant, Daniel G. American Astronomical Society 2016 The Astrophysical Journal Vol.821 No.2
<P>We examine the evolution of the relation between stellar mass surface density, velocity dispersion, and half-light radius-the stellar mass fundamental plane (MFP)-for quiescent galaxies at z < 0.6. We measure the local relation from galaxies in the Sloan Digital Sky Survey and the intermediate redshift relation from similar to 500 quiescent galaxies with stellar masses 10 less than or similar to log(M*/M-circle dot) less than or similar to 11.5. Nearly half of the quiescent galaxies in our intermediate redshift sample are compact. After accounting for important selection and systematic effects, the velocity dispersion distribution of galaxies at intermediate redshifts is similar to that of galaxies in the local universe. Galaxies at z < 0.6 appear to be smaller (less than or similar to 0.1 dex) than galaxies in the local sample. The orientation of the stellar MFP is independent of redshift for massive quiescent galaxies at z < 0.6 and the zero-point evolves by similar to 0.04 dex. Compact quiescent galaxies fall on the same relation as the extended objects. We confirm that compact quiescent galaxies are the tail of the size and mass distribution of the normal quiescent galaxy population.</P>
HECTOMAP AND HORIZON RUN 4: DENSE STRUCTURES AND VOIDS IN THE REAL AND SIMULATED UNIVERSE
Hwang, Ho Seong,Geller, Margaret J.,Park, Changbom,Fabricant, Daniel G.,Kurtz, Michael J.,Rines, Kenneth J.,Kim, Juhan,Diaferio, Antonaldo,Zahid, H. Jabran,Berlind, Perry,Calkins, Michael,Tokarz, Susa American Astronomical Society 2016 The Astrophysical journal Vol.818 No.2
<P>HectoMAP is a dense redshift survey of red galaxies covering a 53 deg(2) strip of the northern sky. HectoMAP is 97% complete for galaxies with r < 20.5, (g-r) > 1.0, and (r -i) > 0.5. The survey enables tests of the physical properties of large-scale structure at intermediate redshift against cosmological models. We use the Horizon Run 4, one of the densest and largest cosmological simulations based on the standard. Cold Dark Matter (Lambda CDM) model, to compare the physical properties of observed large-scale structures with simulated ones in a volume-limited sample covering 8 x 10(6) h(-3) Mpc(3) in the redshift range 0.22 < z < 0.44. We apply the same criteria to the observations and simulations to identify over-and under-dense large-scale features of the galaxy distribution. The richness and size distributions of observed over-dense structures agree well with the simulated ones. Observations and simulations also agree for the volume and size distributions of under-dense structures, voids. The properties of the largest over-dense structure and the largest void in HectoMAP are well within the distributions for the largest structures drawn from 300 Horizon Run 4 mock surveys. Overall the size, richness and volume distributions of observed large-scale structures in the redshift range 0.22 < z < 0.44 are remarkably consistent with predictions of the standard Lambda CDM model.</P>
SHELS: COMPLETE REDSHIFT SURVEYS OF TWO WIDELY SEPARATED FIELDS
Geller, Margaret J.,Hwang, Ho Seong,Dell’Antonio, Ian P.,Zahid, Harus Jabran,Kurtz, Michael J.,Fabricant, Daniel G. American Astronomical Society 2016 The Astrophysical journal, Supplement series Vol.224 No.1
<P>The Smithsonian Hectospec Lensing Survey (SHELS) is a complete redshift survey covering two well-separated fields (F1 and F2) of the Deep Lens Survey (DLS). Both fields are more than 94% complete to a Galactic extinction corrected R-0 = 20.2. Here, we describe the redshift survey of the F1 field centered at R.A.(2000) = 00(h)53(m)25(8).3 and decl.(2000) = 12 degrees 33'55'; like F2, the F1 field covers similar to 4 deg(2). The redshift survey of the F1 field includes 9426 new galaxy redshifts measured with Hectospec on the MMT (published here). As a guide to future uses of the combined survey, we compare the mass metallicity relation and the distributions of D(n)4000 as a function of stellar mass and redshift for the two fields. The mass-metallicity relations differ by an insignificant 1.6 sigma. For galaxies in the stellar mass range 10(10)-10(11) M-circle dot, the increase in the star-forming fraction with redshift is remarkably similar in the two fields. The seemingly surprising 31%-38% difference in the overall galaxy counts in F1 and F2 is probably consistent with the expected cosmic variance given the subtleties of the relative systematics in the two surveys. We also review the DLS cluster detections in the two fields: poorer photometric data for F1 precluded secure detection of the single massive cluster at z = 0.35 that we find in SHELS. Taken together, the two fields include 16,055 redshifts for galaxies with R-0 <= 20.2 and 20,754 redshifts for galaxies with R <= 20.6. These dense surveys in two well-separated fields provide a basis for future investigations of galaxy properties and large-scale structure.</P>
A RISE IN THE IONIZING PHOTONS IN STAR-FORMING GALAXIES OVER THE PAST 8 BILLION YEARS
Kewley, Lisa J.,Zahid, H. Jabran,Geller, Margaret J.,Dopita, Michael A.,Hwang, Ho Seong,Fabricant, Dan IOP Publishing 2015 ASTROPHYSICAL JOURNAL LETTERS - Vol.812 No.2
<P>We investigate the change in ionizing photons in galaxies in the range 0.2 < z < 0.6 using the F2 field of the SHELS complete galaxy redshift survey. We show, for the first time, that while the [O III]/H beta and [O III]/[O II] ratios rise, the [N II]/H alpha and [S II]/H alpha ratios fall significantly over the 0.2 < z < 0.35 redshift range for stellar masses in the range 9.2 < log(M/M-circle dot) < 10.6. The [O III]/H beta and [O III]/[O II] ratios continue to rise across the full 0.2 < z < 0.6 redshift range for stellar masses in the range 9.8 < log(M/M-circle dot) < 10.0. We conclusively rule out active galactic nucleus contamination, a changing ISM pressure, and a change in the hardness of the EUV radiation field as the cause of the change in the line ratios in the range 0.2 < z < 0.35. We find that the ionization parameter rises significantly with redshift (by 0.1-0.25 dex depending on the stellar mass of the sample). We show that the ionization parameter is strongly correlated with the fraction of young-to-old stars, as traced by the H mu equivalent width. We discuss the implications of this result on higher redshift studies, and we consider the implications on the use of standard optical metallicity diagnostics at high redshift.</P>
Bending and free vibration analysis for FGM plates containing various distribution shape of porosity
Hadji, Lazreg,Bernard, Fabrice,Safa, Abdelkader,Tounsi, Abdelouahed Techno-Press 2021 Advances in materials research Vol.10 No.2
In this paper hyperbolic shear deformation plate theory is presented for bending and the free vibration of functionally graded plates with considering porosities that may possibly occur inside the functionally graded materials (FGMs) during their fabrication. Four different porosity types are used for functionally graded plates. Equations of motion are derived from Hamilton's principle. In the solution of the governing equations, the Navier procedure is implemented. In the numerical examples, the effects of the porosity parameters, porosity types and geometry parameters on the bending and free vibration of the functionally graded plates are investigated. It was found that the distribution form of porosity significantly influence the mechanical behavior of FG plates, in terms of deflection, normal, shear stress and frequency.
Lazreg Hadji,Nafissa Zouatnia,Fabrice Bernard 국제구조공학회 2019 Structural Engineering and Mechanics, An Int'l Jou Vol.69 No.2
In this paper, a new higher order shear deformation model is developed for static and free vibration analysis of functionally graded beams with considering porosities that may possibly occur inside the functionally graded materials (FGMs) during their fabrication. Different patterns of porosity distributions (including even and uneven distribution patterns, and the logarithmic-uneven pattern) are considered. In addition, the effect of different micromechanical models on the bending and free vibration response of these beams is studied. Various micromechanical models are used to evaluate the mechanical characteristics of the FG beams whose properties vary continuously across the thickness according to a simple power law. Based on the present higher-order shear deformation model, the equations of motion are derived from Hamilton’s principle. Navier type solution method was used to obtain displacement, stresses and frequencies, and the numerical results are compared with those available in the literature. A comprehensive parametric study is carried out to assess the effects of volume fraction index, porosity fraction index, micromechanical models, mode numbers, and geometry on the bending and natural frequencies of imperfect FG beams.