Galaxy Zoo: Mergers – Dynamical models of interacting galaxies

The dynamical history of most merging galaxies is not well understood. Correlations between galaxy interaction and star formation have been found in previous studies, but require the context of the physical history of merging systems for full insight into the processes that lead to enhanced star formation. We present the results of simulations that reconstruct the orbit trajectories and disturbed morphologies of pairs of interacting galaxies. With the use of a restricted three-body simulation code and the help of citizen scientists, we sample 105 points in parameter space for each system. We demonstrate a successful recreation of the morphologies of 62 pairs of interacting galaxies through the review of more than 3 million simulations. We examine the level of convergence and uniqueness of the dynamical properties of each system. These simulations represent the largest collection of models of interacting galaxies to date, providing a valuable resource for the investigation of mergers. This paper presents the simulation parameters generated by the project. They are now publicly available in electronic format at http://data.galaxyzoo.org/mergers.html. Though our best-fitting model parameters are not an exact match to previously published models, our method for determining uncertainty measurements will aid future comparisons between models. The dynamical clocks from our models agree with previous results of the time since the onset of star formation from starburst models in interacting systems and suggest that tidally induced star formation is triggered very soon after closest approach

Galaxy and Mass Assembly (GAMA): ugriz galaxy luminosity functions

Galaxy and Mass Assembly (GAMA) is a project to study galaxy formation and evolution, combining imaging data from ultraviolet to radio with spectroscopic data from the AAOmega spectrograph on the Anglo-Australian Telescope. Using data from Phase 1 of GAMA, taken over three observing seasons, and correcting for various minor sources of incompleteness, we calculate galaxy luminosity functions (LFs) and their evolution in the ugriz passbands. At low redshift, z < 0.1, we find that blue galaxies, defined according to a magnitude-dependent but non-evolving colour cut, are reasonably well fitted over a range of more than 10 magnitudes by simple Schechter functions in all bands. Red galaxies, and the combined blue plus red sample, require double power-law Schechter functions to fit a dip in their LF faintwards of the characteristic magnitude M* before a steepening faint end. This upturn is at least partly due to dust-reddened disc galaxies. We measure the evolution of the galaxy LF over the redshift range 0.002 < z < 0.5 both by using a parametric fit and by measuring binned LFs in redshift slices. The characteristic luminosity L* is found to increase with redshift in all bands, with red galaxies showing stronger luminosity evolution than blue galaxies. The comoving number density of blue galaxies increases with redshift, while that of red galaxies decreases, consistent with prevailing movement from blue cloud to red sequence. As well as being more numerous at higher redshift, blue galaxies also dominate the overall luminosity density beyond redshifts z≃ 0.2. At lower redshifts, the luminosity density is dominated by red galaxies in the riz bands, and by blue galaxies in u and g

Integrated Nebular Abundances of Disk Galaxies

We study whether integrated optical spectroscopy of a disk galaxy can be used to infer the mean, or characteristic gas-phase oxygen abundance in the presence of systematic effects such as spatial abundance variations, contributions to the integrated emission-line spectrum from diffuse-ionized gas, and dust attenuation. Our sample consists of 14 nearby disk galaxies with integrated spectrophotometry, and observations of more than 250 individual HII regions culled from the literature. We consider both theoretical and empirical strong-line abundance calibrations based on the R23=([OII]+[OIII])/H-beta parameter. We find that the integrated oxygen abundance correlates well with the gas-phase abundance measured at a fixed galactocentric radius, as determined by the HII-region abundance gradient. The typical scatter in the correlation is +/-0.1 dex, independent of the abundance calibration, or whether the observed integrated emission-line fluxes, the reddening-corrected fluxes, or the emission-line equivalent widths are used. Integrated abundances based on the observed fluxes or equivalent widths, however, are susceptible to additional systematic effects of order 0.05-0.1 dex, at least for the range of reddenings and stellar populations spanned by our sample. Unlike the integrated R23 parameter, we find that the integrated [NII]/H-alpha and [SII]/H-alpha ratios are enhanced with respect to line-ratios typical of HII regions, consistent with a modest contribution from diffuse-ionized gas emission. We conclude that the R23 parameter can be used to reliably measure the gas-phase abundances of distant star-forming galaxies.Comment: 12 pages, 7 figures, 4 tables, emulateapj style; ApJ, in press; replaced with accepted version (expanded analysis/discussion, main conclusions unchanged

Isosorbide Mononitrate and Cilostazol Treatment in Patients With Symptomatic Cerebral Small Vessel Disease: The Lacunar Intervention Trial-2 (LACI-2) Randomized Clinical Trial

IMPORTANCE: Cerebral small vessel disease (cSVD) is a common cause of stroke (lacunar stroke), is the most common cause of vascular cognitive impairment, and impairs mobility and mood but has no specific treatment. OBJECTIVE: To test the feasibility, drug tolerability, safety, and effects of 1-year isosorbide mononitrate (ISMN) and cilostazol treatment on vascular, functional, and cognitive outcomes in patients with lacunar stroke. DESIGN, SETTING, AND PARTICIPANTS: The Lacunar Intervention Trial-2 (LACI-2) was an investigator-initiated, open-label, blinded end-point, randomized clinical trial with a 2 × 2 factorial design. The trial aimed to recruit 400 participants from 26 UK hospital stroke centers between February 5, 2018, and May 31, 2021, with 12-month follow-up. Included participants had clinical lacunar ischemic stroke, were independent, were aged older than 30 years, had compatible brain imaging findings, had capacity to consent, and had no contraindications to (or indications for) the study drugs. Data analysis was performed on August 12, 2022. INTERVENTIONS: All patients received guideline stroke prevention treatment and were randomized to ISMN (40-60 mg/d), cilostazol (200 mg/d), ISMN-cilostazol (40-60 and 200 mg/d, respectively), or no study drug. MAIN OUTCOMES: The primary outcome was recruitment feasibility, including retention at 12 months. Secondary outcomes were safety (death), efficacy (composite of vascular events, dependence, cognition, and death), drug adherence, tolerability, recurrent stroke, dependence, cognitive impairment, quality of life (QOL), and hemorrhage. RESULTS: Of the 400 participants planned for this trial, 363 (90.8%) were recruited. Their median age was 64 (IQR, 56.0-72.0) years; 251 (69.1%) were men. The median time between stroke and randomization was 79 (IQR, 27.0-244.0) days. A total of 358 patients (98.6%) were retained in the study at 12 months, with 257 of 272 (94.5%) taking 50% or more of the allocated drug. Compared with those participants not receiving that particular drug, neither ISMN (adjusted hazard ratio [aHR], 0.80 [95% CI, 0.59 to 1.09]; P = .16) nor cilostazol (aHR, 0.77 [95% CI, 0.57 to 1.05]; P = .10) alone reduced the composite outcome in 297 patients. Isosorbide mononitrate reduced recurrent stroke in 353 patients (adjusted odds ratio [aOR], 0.23 [95% CI, 0.07 to 0.74]; P = .01) and cognitive impairment in 308 patients (aOR, 0.55 [95% CI, 0.36 to 0.86]; P = .008). Cilostazol reduced dependence in 320 patients (aHR, 0.31 [95% CI, 0.14 to 0.72]; P = .006). Combination ISMN-cilostazol reduced the composite (aHR, 0.58 [95% CI, 0.36 to 0.92]; P = .02), dependence (aOR, 0.14 [95% CI, 0.03 to 0.59]; P = .008), and any cognitive impairment (aOR, 0.44 [95% CI, 0.23 to 0.85]; P = .02) and improved QOL (adjusted mean difference, 0.10 [95% CI, 0.03 to 0.17]; P = .005) in 153 patients. There were no safety concerns. CONCLUSIONS AND RELEVANCE: These results show that the LACI-2 trial was feasible and ISMN and cilostazol were well tolerated and safe. These agents may reduce recurrent stroke, dependence, and cognitive impairment after lacunar stroke, and they could prevent other adverse outcomes in cSVD. Therefore, both agents should be tested in large phase 3 trials. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT03451591

GAMA: towards a physical understanding of galaxy formation

The Galaxy And Mass Assembly (GAMA) project is the latest in a tradition of large galaxy redshift surveys, and is now underway on the 3.9m Anglo-Australian Telescope at Siding Spring Observatory. GAMA is designed to map extragalactic structures on scales of 1kpc - 1Mpc in complete detail to a redshift of z~0.2, and to trace the distribution of luminous galaxies out to z~0.5. The principal science aim is to test the standard hierarchical structure formation paradigm of Cold Dark Matter (CDM) on scales of galaxy groups, pairs, discs, bulges and bars. We will measure (1) the Dark Matter Halo Mass Function (as inferred from galaxy group velocity dispersions); (2) baryonic processes, such as star formation and galaxy formation efficiency (as derived from Galaxy Stellar Mass Functions); and (3) the evolution of galaxy merger rates (via galaxy close pairs and galaxy asymmetries). Additionally, GAMA will form the central part of a new galaxy database, which aims to contain 275,000 galaxies with multi-wavelength coverage from coordinated observations with the latest international ground- and space-based facilities: GALEX, VST, VISTA, WISE, HERSCHEL, GMRT and ASKAP. Together, these data will provide increased depth (over 2 magnitudes), doubled spatial resolution (0.7"), and significantly extended wavelength coverage (UV through Far-IR to radio) over the main SDSS spectroscopic survey for five regions, each of around 50 deg^2. This database will permit detailed investigations of the structural, chemical, and dynamical properties of all galaxy types, across all environments, and over a 5 billion year timeline.Comment: GAMA overview which appeared in the October 2009 issue of Astronomy & Geophysics, ref: Astron.Geophys. 50 (2009) 5.1

Galaxy Zoo Green Peas: discovery of a class of compact extremely star-forming galaxies

We investigate a class of rapidly growing emission line galaxies, known as ‘Green Peas’, first noted by volunteers in the Galaxy Zoo project because of their peculiar bright green colour and small size, unresolved in Sloan Digital Sky Survey imaging. Their appearance is due to very strong optical emission lines, namely [O iii]λ5007 Å, with an unusually large equivalent width of up to ∼1000 Å. We discuss a well-defined sample of 251 colour-selected objects, most of which are strongly star forming, although there are some active galactic nuclei interlopers including eight newly discovered narrow-line Seyfert 1 galaxies. The star-forming Peas are low-mass galaxies (M∼ 108.5–1010 M⊙) with high star formation rates (∼10 M⊙ yr−1), low metallicities (log[O/H]+ 12 ∼ 8.7) and low reddening [E(B−V) ≤ 0.25] and they reside in low-density environments. They have some of the highest specific star formation rates (up to ∼10−8 yr−1) seen in the local Universe, yielding doubling times for their stellar mass of hundreds of Myr. The few star-forming Peas with Hubble Space Telescope imaging appear to have several clumps of bright star-forming regions and low surface density features that may indicate recent or ongoing mergers. The Peas are similar in size, mass, luminosity and metallicity to luminous blue compact galaxies. They are also similar to high-redshift ultraviolet-luminous galaxies, e.g. Lyman-break galaxies and Lyα emitters, and therefore provide a local laboratory with which to study the extreme star formation processes that occur in high-redshift galaxies. Studying starbursting galaxies as a function of redshift is essential to understanding the build up of stellar mass in the Universe

The SOS Pilot Study: a RCT of routine oxygen supplementation early after acute stroke—effect on recovery of neurological function at one week

Mild hypoxia is common after stroke and associated with poor long-term outcome. Oxygen supplementation could prevent hypoxia and improve recovery. A previous study of routine oxygen supplementation showed no significant benefit at 7 and 12 months. This pilot study reports the effects of routine oxygen supplementation for 72 hours on oxygen saturation and neurological outcomes at 1 week after a stroke

Dysfunctional play and dopamine physiology in the Fischer 344 rat

Juvenile Fischer 344 rats are known to be less playful than other inbred strains, although the neurobiological substrate(s) responsible for this phenotype is uncertain. In the present study, Fischer 344 rats were compared to the commonly used outbred Sprague-Dawley strain on several behavioral and physiological parameters in order to ascertain whether the lack of play may be related to compromised activity of brain dopamine (DA) systems. As expected, Fischer 344 rats were far less playful than Sprague-Dawley rats, with Fischer 344 rats less likely to initiate playful contacts with a playful partner and less likely to respond playfully to these contacts. We also found that Fischer 344 rats showed less of a startle response and greater pre-pulse inhibition (PPI), especially at higher prepulse intensities. The increase in PPI seen in the Fischer 344 rat could be due to reduced DA modulation of sensorimotor gating and neurochemical measures were consistent with Fischer 344 rats releasing less DA than Sprague-Dawley rats. Fast scan cyclic voltammetry (FSCV) revealed Fischer 344 rats had less evoked DA release in dorsal and ventral striatal brain slices and high-performance liquid chromatography revealed Fischer 344 rats to have less DA turnover in the striatum and prefrontal cortex. We also found DA-dependent forms of cortical plasticity were deficient in the striatum and prefrontal cortex of the Fischer 344 rat. Taken together, these data indicate that deficits in play and enhanced PPI of Fischer 344 rats may be due to reduced DA modulation of corticostriatal and mesolimbic/mesocortical circuits critical to the execution of these behaviors

Interferon lambda 4 impacts the genetic diversity of hepatitis C virus

Hepatitis C virus (HCV) is a highly variable pathogen that frequently establishes chronic infection. This genetic variability is affected by the adaptive immune response but the contribution of other host factors is unclear. Here, we examined the role played by interferon lambda-4 (IFN-λ4) on HCV diversity; IFN-λ4 plays a crucial role in spontaneous clearance or establishment of chronicity following acute infection. We performed viral genome-wide association studies using human and viral data from 485 patients of white ancestry infected with HCV genotype 3a. We demonstrate that combinations of host genetic variants, which determine IFN-λ4 protein production and activity, influence amino acid variation across the viral polyprotein - not restricted to specific viral proteins or HLA restricted epitopes - and modulate viral load. We also observed an association with viral di-nucleotide proportions. These results support a direct role for IFN-λ4 in exerting selective pressure across the viral genome, possibly by a novel mechanism