ABSTRACT
We use KiDS weak lensing data to measure variations in mean halo mass as a function of several key galaxy properties (namely stellar colour, specific star formation rate, Sérsic index, and ...effective radius) for a volume-limited sample of GAMA galaxies in a narrow stellar mass range M* ∼ (2–5) × 1010 M⊙. This mass range is particularly interesting, inasmuch as it is where bimodalities in galaxy properties are most pronounced, and near to the break in both the galaxy stellar mass function and the stellar-to-halo mass relation (SHMR). In this narrow mass range, we find that both size and Sérsic index are better predictors of halo mass than either colour or SSFR, with the data showing a slight preference for Sérsic index. In other words, we find that mean halo mass is more tightly correlated with galaxy structure than either past star formation history or current star formation rate. Our results lead to an approximate lower bound on the dispersion in halo masses among log M* ≈ 10.5 galaxies: We find that the dispersion is ≳0.3 dex. This would imply either that offsets from the mean SHMR are closely coupled to size/structure or that the dispersion in the SHMR is larger than what past results have suggested. Our results thus provide new empirical constraints on the relationship between stellar and halo mass assembly at this particularly interesting mass range.
We systematically measure the gas-phase metallicities and the mass-metallicity relation of a large sample of local active galaxies for the first time. Observed emission-line fluxes from the Sloan ...Digital Sky Survey are compared to a four-dimensional grid of photoionization models using the Bayesian parameter estimation code NebulaBayes. For the first time we take into account arbitrary mixing between H ii region and narrow-line region (NLR) emission, and the models are also varied with metallicity, ionization parameter in the NLR, and gas pressure. The active galactic nucleus oxygen abundance is found to increase by Δ O H ∼ 0.1 dex as a function of host galaxy stellar mass over the range 10.1 < log M * M < 11.3 . We also measure the metallicity and ionization parameter of 231,000 star-forming galaxies for comparison with the sample of 7670 Seyfert 2 galaxies. A systematic offset in oxygen abundance of 0.09 dex is observed between the mass-metallicity relations of the star-forming and active galaxies. We investigate potential causes of the offset, including sample selection and the treatment in the models of diffuse ionized gas, pressure, and ionization parameter. We cannot identify the major cause(s), but suspect contributions due to deficiencies in modeling the ionizing spectra and the treatment of dust physics. Optical diagnostic diagrams are presented with the star-forming and Seyfert data colored by the inferred oxygen abundance, ionization parameter, and gas pressure, clearly illustrating the trends in these quantities.
We demonstrate a novel technology that combines the power of the multi-object spectrograph with the spatial multiplex advantage of an integral field spectrograph (IFS). The Sydney-AAO (Australian ...Astronomical Observatory) Multi-object IFS (SAMI) is a prototype wide-field system at the Anglo-Australian Telescope (AAT) that allows 13 imaging fibre bundles ('hexabundles') to be deployed over a 1-degree diameter field of view. Each hexabundle comprises 61 lightly fused multi-mode fibres with reduced cladding and yields a 75 per cent filling factor. Each fibre core diameter subtends 1.6 arcsec on the sky and each hexabundle has a field of view of 15 arcsec diameter. The fibres are fed to the flexible AAOmega double-beam spectrograph, which can be used at a range of spectral resolutions (R=λ/δλ≈ 1700-13 000) over the optical spectrum (3700-9500 Å). We present the first spectroscopic results obtained with SAMI for a sample of galaxies at z≈ 0.05. We discuss the prospects of implementing hexabundles at a much higher multiplex over wider fields of view in order to carry out spatially resolved spectroscopic surveys of 104-105 galaxies.
We present measurements of the radial gravitational acceleration around isolated galaxies, comparing the expected gravitational acceleration given the baryonic matter (
g
bar
) with the observed ...gravitational acceleration (
g
obs
), using weak lensing measurements from the fourth data release of the Kilo-Degree Survey (KiDS-1000). These measurements extend the radial acceleration relation (RAR), traditionally measured using galaxy rotation curves, by 2 decades in
g
obs
into the low-acceleration regime beyond the outskirts of the observable galaxy. We compare our RAR measurements to the predictions of two modified gravity (MG) theories: modified Newtonian dynamics and Verlinde’s emergent gravity (EG). We find that the measured relation between
g
obs
and
g
bar
agrees well with the MG predictions. In addition, we find a difference of at least 6
σ
between the RARs of early- and late-type galaxies (split by Sérsic index and
u
−
r
colour) with the same stellar mass. Current MG theories involve a gravity modification that is independent of other galaxy properties, which would be unable to explain this behaviour, although the EG theory is still limited to spherically symmetric static mass models. The difference might be explained if only the early-type galaxies have significant (
M
gas
≈
M
⋆
) circumgalactic gaseous haloes. The observed behaviour is also expected in Λ-cold dark matter (ΛCDM) models where the galaxy-to-halo mass relation depends on the galaxy formation history. We find that MICE, a ΛCDM simulation with hybrid halo occupation distribution modelling and abundance matching, reproduces the observed RAR but significantly differs from BAHAMAS, a hydrodynamical cosmological galaxy formation simulation. Our results are sensitive to the amount of circumgalactic gas; current observational constraints indicate that the resulting corrections are likely moderate. Measurements of the lensing RAR with future cosmological surveys (such as Euclid) will be able to further distinguish between MG and ΛCDM models if systematic uncertainties in the baryonic mass distribution around galaxies are reduced.
We simultaneously present constraints on the stellar-to-halo mass relation for central and satellite galaxies through a weak lensing analysis of spectroscopically classified galaxies. Using ...overlapping data from the fourth data release of the Kilo-Degree Survey (KiDS), and the Galaxy And Mass Assembly survey (GAMA), we find that satellite galaxies are hosted by halo masses that are 0.53 ± 0.39 dex (68% confidence, 3
σ
detection) smaller than those of central galaxies of the same stellar mass (for a stellar mass of log(
M
⋆
/
M
⊙
) = 10.6). This is consistent with galaxy formation models, whereby infalling satellite galaxies are preferentially stripped of their dark matter. We find consistent results with similar uncertainties when comparing constraints from a standard azimuthally averaged galaxy-galaxy lensing analysis and a two-dimensional likelihood analysis of the full shear field. As the latter approach is somewhat biased due to the lens incompleteness and as it does not provide any improvement to the precision when applied to actual data, we conclude that stacked tangential shear measurements are best-suited for studies of the galaxy-halo connection.
Based on data from the Galaxy and Mass Assembly (GAMA) survey, we report on the discovery of structures that we refer to as 'tendrils' of galaxies: coherent, thin chains of galaxies that are rooted ...in filaments and terminate in neighbouring filaments or voids. On average, tendrils contain six galaxies and span 10 h
−1 Mpc. We use the so-called line correlation function to prove that tendrils represent real structures rather than accidental alignments. We show that voids found in the Sloan Digital Sky Survey, 7th data release survey that overlap with GAMA regions contain a large number of galaxies, primarily belonging to tendrils. This implies that void sizes are strongly dependent on the number density and sensitivity limits of a survey. We caution that galaxies in low-density regions, which may be defined as 'void galaxies,' will have local galaxy number densities that depend on such observational limits and are likely higher than those can be directly measured.
We use the Galaxy And Mass Assembly (GAMA) survey to measure the local Universe mass-dependent merger fraction and merger rate using galaxy pairs and the CAS (concentration, asymmetry, and ...smoothness) structural method, which identifies highly asymmetric merger candidate galaxies. Our goals are to determine which types of mergers produce highly asymmetrical galaxies and to provide a new measurement of the local galaxy major merger rate. We examine galaxy pairs at stellar mass limits down to M* = 10... M... with mass ratios of <100:1 and line-of-sight velocity differences of ... < 500 km s... We find a significant increase in mean asymmetries for projected separations less than the sum of the individual galaxy's Petrosian 90 radii. For systems in major merger pairs with mass ratios of <4:1, both galaxies in the pair show a strong increase in asymmetry, while in minor merger systems (with mass ratios of >4:1) the lower mass companion becomes highly asymmetric, whereas the larger galaxy is much less affected. The fraction of highly asymmetric paired galaxies which have a major merger companion is highest for the most massive galaxies and drops progressively with decreasing mass. We calculate that the mass-dependent major merger fraction is fairly constant at ~1.3-2 per cent within 109.5 < M* < 10... M..., and increases to ~4 per cent at lower masses. When the observability time-scales are taken into consideration, the major merger rate is found to approximately triple over the mass range we consider. The total comoving volume major merger rate over the range 108.0 < M* < 10... M... is (1.2 plus or minus 0.5) x 10... h... Mpc-3 Gyr... (ProQuest: ... denotes formulae/symbols omitted.)
The ASKAP-EMU survey is a deep wide-field radio continuum survey designed to cover the entire southern sky and a significant fraction of the northern sky up to +30°. Here, we report a discovery of a ...radio relic in the merging cluster SPT-CL J2023-5535 at z = 0.23 from the ASKAP-EMU pilot 300 square degree survey (800-1088 MHz). The deep high-resolution data reveal a ∼2 Mpc scale radio halo elongated in the east-west direction, coincident with the intracluster gas. The radio relic is located at the western edge of this radio halo stretched ∼0.5 Mpc in the north-south orientation. The integrated spectral index of the radio relic within the narrow bandwidth is . Our weak-lensing analysis shows that the system is massive ( ) and composed of at least three subclusters. We suggest a scenario, wherein the radio features arise from the collision between the eastern and middle subclusters. Our discovery illustrates the effectiveness of the ASKAP-EMU survey in detecting diffuse emissions in galaxy clusters and when completed, the survey will greatly increase the number of merging cluster detections with diffuse radio emissions.
VL-2397 is an antifungal drug with a novel mechanism of action, rapid fungicidal
activity, and potent
activity against
, including azole-resistant strains. VL2397-101, a phase 1 first-in-human, ...randomized, double-blind, placebo-controlled dose-escalation study, was conducted in healthy adults to determine the safety, tolerability, and pharmacokinetics (PK) of single and multiple ascending intravenous (i.v.) doses of VL-2397. All dosing cohorts were fully enrolled; all subjects completed the safety follow-up. A safety committee reviewed the safety data for each dosing cohort prior to recommending the initiation of each subsequent cohort. No serious adverse events (SAEs) occurred; the majority of treatment-emergent adverse events (TEAEs) were mild and self-limited. The most common drug-related TEAEs were infusion site reactions. No clinically concerning trends were noted in vital signs, electrocardiograms, physical examinations, or safety laboratory results. Following single infusions of VL-2397, the overall and maximum exposures rose less than proportionally with increasing doses from 3 mg to 1,200 mg as indicated by area under the concentration-time curve over 24 h (AUC
) and maximum concentration (
). No signs of VL-2397 accumulation were observed following i.v. infusions of 300, 600, and 1,200 mg every 24 h (q24h) for 7 days. Renal elimination played a major role in total body clearance, with up to 47% of unmetabolized drug in urine 24 h after administration at single doses of >30 mg. Overall, VL-2397 dosing in the study appeared to be safe and well tolerated in the healthy subjects. The safety profile, consistent PK, and lack of drug accumulation support further development of VL-2397 in patients with invasive aspergillosis.
We report the morphological classification of 3727 galaxies from the Galaxy and Mass Assembly survey with M
r
< −17.4 mag and in the redshift range 0.025 < z < 0.06 (2.1 × 105 Mpc3) into E, S0-Sa, ...SB0-SBa, Sab-Scd, SBab-SBcd, Sd-Irr and little blue spheroid classes. Approximately 70 per cent of galaxies in our sample are disc-dominated systems, with the remaining ∼30 per cent spheroid dominated. We establish the robustness of our classifications, and use them to derive morphological-type luminosity functions and luminosity densities in the ugrizYJHK passbands, improving on prior studies that split by global colour or light profile shape alone. We find that the total galaxy luminosity function is best described by a double-Schechter function while the constituent morphological-type luminosity functions are well described by a single-Schechter function. These data are also used to derive the star formation rate densities for each Hubble class, and the attenuated and unattenuated (corrected for dust) cosmic spectral energy distributions, i.e. the instantaneous energy production budget. While the observed optical/near-IR energy budget is dominated 58:42 by galaxies with a significant spheroidal component, the actual energy production rate is reversed, i.e. the combined disc-dominated populations generate ∼1.3 times as much energy as the spheroid-dominated populations. On the grandest scale, this implies that chemical evolution in the local Universe is currently largely confined to mid-type spiral classes like our Milky Way.
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