Magnetars are a sizable subclass of the neutron star census. Their very high
magnetic field strengths are thought to be a consequence of rapid (millisecond)
rotation at birth in a successful ...core-collapse supernova. In their first tens
of seconds of existence, magnetars transition from hot, extended
``proto-''magnetars to the cooled and magnetically-dominated objects we
identify $\sim10^4$ years later as Soft Gamma-ray Repeaters (SGRs) and
Anamolous X-ray Pulsars (AXPs). Millisecond proto-magnetar winds during this
cooling phase likewise transition from non-relativistic and thermally-driven to
magneto-centrifugally-driven, and finally to relativistic and Poynting-flux
dominated. Here we review the basic considerations associated with that
transition. In particular, we discuss the spindown of millisecond
proto-magnetars throughout the Kelvin-Helmholtz cooling epoch. Because of their
large reservoir of rotational energy, their association with supernovae, and
the fact that their winds are expected to become highly relativistic in the
seconds after their birth, proto-magnetars have been suggested as the central
engine of long-duration gamma ray bursts. We discuss some of the issues and
outstanding questions in assessing them as such.
We evaluate radiation pressure from starlight on dust as a feedback mechanism in star-forming galaxies by comparing the luminosity and flux of star-forming systems to the dust Eddington limit. The ...linear LFIR--L'HCN correlation provides evidence that galaxies may be regulated by radiation pressure feedback. We show that star-forming galaxies approach but do not dramatically exceed Eddington, but many systems are significantly below Eddington, perhaps due to the "intermittency" of star formation. Better constraints on the dust-to-gas ratio and the CO- and HCN-to-H2 conversion factors are needed to make a definitive assessment of radiation pressure as a feedback mechanism.
The All-Sky Automated Survey for Supernovae (ASAS-SN) is the first optical survey to routinely monitor the whole sky with a cadence of \(\sim2-3\) days down to V\(\lesssim17\) mag. ASAS-SN has ...monitored the whole sky since 2014, collecting \(\sim100-500\) epochs of observations per field. The V-band light curves for candidate variables identified during the search for supernovae are classified using a random forest classifier and visually verified. We present a catalog of 66,179 bright, new variable stars discovered during our search for supernovae, including 27,479 periodic variables and 38,700 irregular variables. V-band light curves for the ASAS-SN variables are available through the ASAS-SN variable stars database (https://asas-sn.osu.edu/variables). The database will begin to include the light curves of known variable stars in the near future along with the results for a systematic, all-sky variability survey.
I discuss neutrino production in supernovae (SNe) and the detection of both
Galactic core collapse events and the diffuse extra-galactic MeV neutrino
background expected from the integrated history ...of star formation. In
particular, I consider what processes might affect our expectations for both. I
focus on ``rapid'' rotation, defined as leading to millisecond initial neutron
star spin periods. Rotation affects the neutrino luminosity, the average
neutrino energy, the duration of the Kelvin-Helmholtz cooling epoch, and the
ratios of luminosities and average energies between neutrino species; it can
strongly suppresses the anti-electron as well as mu, anti-mu, tau, and anti-tau
neutrino fluxes relative to those for the electron neutrinos. As a result,
depending on the prevalence of rapid rotation in SN progenitors through cosmic
time, this may affect predictions for the MeV neutrino background and the
history of nucleosynthetic enrichment. I emphasize connections between the MeV
neutrino background and tracers of the star formation rate density at high
redshift in other neutrino and photon wavebands.
DNA variants underlying the inheritance of risk for common diseases are expected to have a wide range of population allele frequencies. The detection and scoring of the rare alleles (at frequencies ...of <0.01) presents significant practical problems, including the requirement for large sample sizes and the limitations inherent in current methodologies for allele discrimination. In the present report, we have applied mutational spectrometry based on constant denaturing capillary electrophoresis (CDCE) to DNA pools from large populations in order to improve the prospects of testing the role of rare variants in common diseases on a large scale. We conducted a pilot study of the cytotoxic T lymphocyte-associated antigen-4 gene (CTLA4) in type 1 diabetes (T1D). A total of 1228 bp, comprising 98% of the CTLA4 coding sequence, all adjacent intronic mRNA splice sites, and a 3' UTR sequence were scanned for unknown point mutations in pools of genomic DNA from a control population of 10,464 young American adults and two T1D populations, one American (1799 individuals) and one from the United Kingdom (2102 individuals). The data suggest that it is unlikely that rare variants in the scanned regions of CTLA4 represent a significant proportion of T1D risk and illustrate that CDCE-based mutational spectrometry of DNA pools offers a feasible and cost-effective means of testing the role of rare variants in susceptibility to common diseases.
Radiation pressure from the absorption and scattering of starlight by dust grains may be an important feedback mechanism in regulating star-forming galaxies. We compile data from the literature on ...star clusters, star-forming subregions, normal star-forming galaxies, and starbursts to assess the importance of radiation pressure on dust as a feedback mechanism, by comparing the luminosity and flux of these systems to their dust Eddington limit. This exercise motivates a novel interpretation of the Schmidt Law, the LIR-L'CO correlation, and the LIR-L'HCN correlation. In particular, the linear LIR-L'HCN correlation is a natural prediction of radiation pressure regulated star formation. Overall, we find that the Eddington limit sets a hard upper bound to the luminosity of any star-forming region. Importantly, however, many normal star-forming galaxies have luminosities significantly below the Eddington limit. We explore several explanations for this discrepancy, especially the role of "intermittency" in normal spirals - the tendency for only a small number of subregions within a galaxy to be actively forming stars at any moment because of the time-dependence of the feedback process and the luminosity evolution of the stellar population. If radiation pressure regulates star formation in dense gas, then the gas depletion timescale is 6 Myr, in good agreement with observations of the densest starbursts. Finally, we highlight the importance of observational uncertainties - namely, the dust-to-gas ratio and the CO-H2 and HCN-H2 conversion factors - that must be understood before a definitive assessment of radiation pressure as a feedback mechanism in star-forming galaxies.
We present a K-band spectroscopic study of the stellar and gas kinematics, mass distribution, and stellar populations of the archetypical starburst galaxy M82. Our results are based on a single ...spectrum at a position angle of 67.5 degrees through the K-band nucleus. We used the CO stellar absorption band head at 2.29 {\mu}m (CO_2.29) to measure the rotation curve out to nearly 4 kpc radius on both the eastern and western sides of the galaxy. Our data show that the rotation curve is flat from 1 - 4 kpc. This stands in sharp contrast to some previous studies, which have interpreted H I and CO emission-line position-velocity diagrams as evidence for a declining rotation curve. The kinematics of the Br\gamma, H_2, and He I emission lines are consistent with, although characterized by slightly higher velocities than, the stellar kinematics. We derived M82's mass distribution from our stellar kinematic measurements and estimate its total dynamical mass is ~10^10 Msun. We measured the equivalent width of CO_2.29 (W_2.29) as a function of distance from the center of the galaxy to investigate the spatial extent of the red supergiant (RSG) population. The variation in W_2.29 with radius clearly shows that RSGs dominate the light inside 500 pc radius. M82's superwind is likely launched from this region, where we estimate the enclosed mass is <= 2 x 10^9 Msun.
We construct one-zone steady-state models of cosmic ray (CR) injection, cooling, and escape over the entire dynamic range of the FIR-radio correlation (FRC), from normal galaxies to starbursts, over ...the redshift interval 0 <= z <= 10. Normal galaxies with low star-formation rates become radio-faint at high z, because Inverse Compton (IC) losses off the CMB cool CR electrons and positrons rapidly, suppressing their nonthermal radio emission. However, we find that this effect occurs at higher redshifts than previously expected, because escape, bremsstrahlung, ionization, and starlight IC losses act to counter this effect and preserve the radio luminosity of galaxies. The radio dimming of star-forming galaxies at high z is not just a simple competition between magnetic field energy density and the CMB energy density; the CMB must also compete with every other loss process. We predict relations for the critical redshift when radio emission is significantly suppressed compared to the z ~ 0 FRC as a function of star-formation rate per unit area. Additionally, we provide a quantitative explanation for the relative radio brightness of some high-z submillimeter galaxies. We show that at fixed star formation rate surface density, galaxies with larger CR scale heights are radio bright with respect to the FRC, because of weaker bremsstrahlung and ionization losses compared to compact starbursts. We predict that these "puffy starbursts" should have steeper radio spectra than compact galaxies with the same star-formation rate surface density. We find that radio bright submillimeter galaxies alone cannot explain the excess radio emission reported by ARCADE2, but they may significantly enhance the diffuse radio background with respect to a naive application of the z ~ 0 FRC.
Galactic outflows of low ionization, cool gas are ubiquitous in local starburst galaxies, and in the majority of galaxies at high redshift. How these cool outflows arise is still in question. Hot gas ...from supernovae has long been suspected as the primary driver, but this mechanism suffers from its tendency to destroy the cool gas as the latter is accelerated. We propose a modification of the supernova scenario that overcomes this difficulty. Star formation is observed to take place in clusters; in a given galaxy, the bulk of the star formation is found in the ~20 most massive clusters. We show that, for L* galaxies, the radiation pressure from clusters with M>10^6 M_sun is able to expel the surrounding gas at velocities in excess of the circular velocity of the disk galaxy. This cool gas can travel above the galactic disk in less than 2 Myr, well before any supernovae erupt in the driving cluster. Once above the disk, the cool outflowing gas is exposed to radiation, and supernovae induced hot gas outflows, from other clusters in the disk, which drive it to distances of several tens to hundreds of kpc. Because the radiatively driven clouds grow in size as they travel, and because the hot gas is more dilute at large distance, the clouds are less subject to destruction if they do eventually encounter hot gas. Therefore, unlike wind driven clouds, radiatively driven clouds can survive to distances ~50 kpc. We identify these cluster-driven winds with large-scale galactic outflows. Another implication of our model is that only starburst galaxies, where massive clusters reside, are able to drive winds cold outflows on galactic scales via this mechanism. We find that the critical star formation rates above which large scale cool outflows will be launched to be ~0.1 M_sun/yr/kpc^2, which is in good agreement with observations.
