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Full-Text Articles in Physical Sciences and Mathematics
Galaxy And Mass Assembly (Gama): Accurate Number Densities And Environments Of Massive Ultra-Compact Galaxies At 0.02 < Z < 0.3, F. Buitrago, I. Ferreras, L. S. Kelvin, I. K. Baldry, L. Davies, J. Angthopo, S. Khochfar, A. M. Hopkins, S. P. Driver, S. Brough, J. Sabater, C. J. Conselice, J. Liske, Benne W. Holwerda, M. N. Bremer, S. Phillipps, A. R. López-Sánchez, A. W. Graham
Galaxy And Mass Assembly (Gama): Accurate Number Densities And Environments Of Massive Ultra-Compact Galaxies At 0.02 < Z < 0.3, F. Buitrago, I. Ferreras, L. S. Kelvin, I. K. Baldry, L. Davies, J. Angthopo, S. Khochfar, A. M. Hopkins, S. P. Driver, S. Brough, J. Sabater, C. J. Conselice, J. Liske, Benne W. Holwerda, M. N. Bremer, S. Phillipps, A. R. López-Sánchez, A. W. Graham
Faculty Scholarship
Context. Massive ultra-compact galaxies (MUGs) are common at z = 2-3, but very rare in the nearby Universe. Simulations predict that the few surviving MUGs should reside in galaxy clusters, whose large relative velocities prevent them from merging, thus maintaining their original properties (namely stellar populations, masses, sizes and dynamical state). Aims. Our goal is to obtain a complete census of the MUG population at 0.02 < z < 0.3, determining the number density, population properties and environment. Methods. We have taken advantage of the high-completeness, large-area spectroscopic GAMA survey, complementing it with deeper imaging from the KiDS and VIKING surveys. We find a set of 22 bona-fide MUGs, defined as having high stellar mass (> 8 × 1010 M™) and compact size (Re < 2 kpc). An additional set of seven lower-mass objects (6 × 1010 < Ma/M™ < 8 × 1010) are also potential candidates according to typical mass uncertainties. Results. The comoving number density of MUGs at low redshift (z < 0.3) is constrained at (1.0 ± 0.4)×10-6 Mpc-3, consistent with galaxy evolution models. However, we find a mixed distribution of old and young galaxies, with a quarter of the sample representing (old) relics. MUGs have a predominantly early or swollen disk morphology (Sérsic index 1 < n < 2.5) with high stellar surface densities (â Σea ∼1010 M™ Kpc-2). Interestingly, a large fraction feature close companions- A t least in projection-suggesting that many (but not all) reside in the central regions of groups. Halo masses show these galaxies inhabit average-mass groups. Conclusions. As MUGs are found to be almost equally distributed among environments of different masses, their relative fraction is higher in more massive overdensities, matching the expectations that some of these galaxies fell in these regions at early times. However, there must be another channel leading some of these galaxies to an abnormally low merger history because our sample shows a number of objects that do not inhabit particularly dense environments.
Galaxy And Mass Assembly (Gama): Gas Fuelling Of Spiral Galaxies In The Local Universe Ii. - Direct Measurement Of The Dependencies On Redshift And Host Halo Mass Of Stellar Mass Growth In Central Disc Galaxies, M. W. Grootes, A. Dvornik, R. J. Laureijs, R. J. Tuffs, C. C. Popescu, A. S.G. Robotham, J. Liske, M. J.I. Brown, Benne W. Holwerda, L. Wang
Galaxy And Mass Assembly (Gama): Gas Fuelling Of Spiral Galaxies In The Local Universe Ii. - Direct Measurement Of The Dependencies On Redshift And Host Halo Mass Of Stellar Mass Growth In Central Disc Galaxies, M. W. Grootes, A. Dvornik, R. J. Laureijs, R. J. Tuffs, C. C. Popescu, A. S.G. Robotham, J. Liske, M. J.I. Brown, Benne W. Holwerda, L. Wang
Faculty Scholarship
We present a detailed analysis of the specific star formation rate-stellar mass (sSFR-M*) of z ≤ 0.13 disc central galaxies using a morphologically selected mass-complete sample (M* ≥ 109.5M⊙). Considering samples of grouped and ungrouped galaxies, we find the sSFR-M* relations of disc-dominated central galaxies to have no detectable dependence on host dark-matter halo (DMH) mass, even where weak-lensing measurements indicate a difference in halo mass of a factor ≳ 5.We further detect a gradual evolution of the sSFR-M* relation of non-grouped (field) central disc galaxies with redshift, even over a Δz ≈ 0.04 (≈5 × 108 yr) interval, while …
Galaxy And Mass Assembly (Gama): Impact Of The Group Environment On Galaxy Star Formation, S. Barsanti, M. S. Owers, S. Brough, L. J.M. Davies, S. P. Driver, M. L.P. Gunawardhana, Benne W. Holwerda, J. Liske, J. Loveday, K. A. Pimbblet, A. S.G. Robotham, E. N. Taylor
Galaxy And Mass Assembly (Gama): Impact Of The Group Environment On Galaxy Star Formation, S. Barsanti, M. S. Owers, S. Brough, L. J.M. Davies, S. P. Driver, M. L.P. Gunawardhana, Benne W. Holwerda, J. Liske, J. Loveday, K. A. Pimbblet, A. S.G. Robotham, E. N. Taylor
Faculty Scholarship
We explore how the group environment may affect the evolution of star-forming galaxies. We select 1197 Galaxy And Mass Assembly groups at 0.05 ≤ z ≤ 0.2 and analyze the projected phase space (PPS) diagram, i.e., the galaxy velocity as a function of projected group-centric radius, as a local environmental metric in the low-mass halo regime 1012 ≤ (M 200/M o) < 1014. We study the properties of star-forming group galaxies, exploring the correlation of star formation rate (SFR) with radial distance and stellar mass. We find that the fraction of star-forming group members is higher in the PPS regions dominated by recently accreted galaxies, whereas passive galaxies dominate the virialized regions. We observe a small decline in specific SFR of star-forming galaxies toward the group center by a factor ∼1.2 with respect to field galaxies. Similar to cluster studies, we conclude for low-mass halos that star-forming group galaxies represent an infalling population from the field to the halo and show suppressed star formation.