We investigate large-scale galactic winds driven by momentum deposition. Momentum injection is provided by (1) radiation pressure produced by the continuum absorption and scattering of photons on dust grains and (2) supernovae (momentum injection by supernovae is important even if the supernovae energy is radiated away). Radiation can be produced by a starburst or AGN activity.We argue that momentum-driven winds are an efficient mechanism for feedback during the formation of galaxies. We show that above a limiting luminosity, momentum deposition from star formation can expel a significant fraction of the gas in a galaxy. The limiting, Eddington-like luminosity is L M ≃ (4 f g c/G) σ 4 , where σ is the galaxy velocity dispersion and f g is the gas fraction; the subscript M refers to momentum driving. A starburst that attains L M moderates its star formation rate and its luminosity does not increase significantly further. We argue that ellipticals attain this limit during their growth at z 1 and that this is the origin of the Faber-Jackson relation. We show that Lyman break galaxies and ultra-luminous infrared galaxies have luminosities near L M . Since these starbursting galaxies account for a significant fraction of the star formation at z 1, this supports our hypothesis that much of the observed stellar mass in early type galaxies was formed during Eddington-limited star formation.Star formation is unlikely to efficiently remove gas from very small scales in galactic nuclei, i.e., scales much smaller than that of a nuclear starburst. This gas is available to fuel a central black hole (BH). We argue that a BH clears gas out of its galactic nucleus when the luminosity of the BH itself reaches ≈ L M . This shuts off the fuel supply to the BH and may also terminate star formation in the surrounding galaxy. As a result, the BH mass is fixed to be M BH ≃ ( f g κ es /πG 2 )σ 4 , where κ es is the electron scattering opacity. This limit is in accord with the observed M BH − σ relation.

We consider the structure of marginally Toomre-stable starburst disks under the assumption that radiation pressure on dust grains provides the dominant vertical support against gravity. This assumption is particularly appropriate when the disk is optically thick to its own infrared radiation, as in the central regions of Ultraluminous Infrared Galaxies (ULIRGs). We argue that because the disk radiates at its Eddington limit (for dust), the "Schmidt-law" for star formation changes in the optically-thick limit, with the star formation rate per unit area scaling asΣ ⋆ ∝ Σ g /κ, where Σ g is the gas surface density and κ is the mean opacity of the disk. Our calculations further show that optically thick starburst disks have a characteristic flux, star formation rate per unit area, and dust effective temperature of F ∼ 10 13 L ⊙ kpc −2 ,Σ ⋆ ∼ 10 3 M ⊙ yr −1 kpc −2 , and T eff ∼ 90 K, respectively. We compare our model predictions with observations of ULIRGs and find good agreement.We extend our model of starburst disks from many-hundred parsec scales to sub-parsec scales and address the problem of fueling active galactic nuclei (AGN). We assume that angular momentum transport proceeds via global torques (e.g., spiral waves, winds, or a central bar) rather than a local viscosity. We consistently account for the radial depletion of gas due to star formation and find a strong bifurcation between two classes of disk models: (1) solutions with a starburst on large scales that consumes all of the gas with little or no fueling of a central AGN and (2) models with an outer large-scale starburst accompanied by a more compact starburst on 1 − 10 pc scales and a bright central AGN. The luminosity of the latter models is in many cases dominated by the AGN, although these disk solutions exhibit a broad mid-to far-infrared peak from star formation. We show that the vertical thickness of the starburst disk on parsec scales can approach h ∼ r, perhaps accounting for the nuclear obscuration in some Type 2 AGN. We also argue that the disk of young stars in the Galactic Center may be the remnant of such a compact nuclear starburst.

The All-Sky Automated Survey for Supernovae (ASAS-SN) is working towards imaging the entire visible sky every night to a depth of V ∼ 17 mag. The present data covers the sky and spans ∼ 2-5 years with ∼ 100-400 epochs of observation. The data should contain some ∼ 1 million variable sources, and the ultimate goal is to have a database of these observations publicly accessible. We describe here a first step, a simple but unprecedented web interface https://asas-sn.osu.edu/ that provides an up to date aperture photometry light curve for any user-selected sky coordinate. Because the light curves are produced in real time, this web tool is relatively slow and can only be used for small samples of objects. However, it also imposes no selection bias on the part of the ASAS-SN team, allowing the user to obtain a light curve for any point on the celestial sphere. We present the tool, describe its capabilities, limitations, and known issues, and provide a few illustrative examples.

Long duration gamma‐ray bursts (GRBs) originate from the core collapse of massive stars, but the identity of the central engine remains elusive. Previous work has shown that rapidly spinning, strongly magnetized protoneutron stars (‘millisecond protomagnetars’) produce outflows with energies, time‐scales and magnetizations σ0 (maximum Lorentz factor) that are consistent with those required to produce long duration GRBs. Here we extend this work in order to construct a self‐consistent model that directly connects the properties of the central engine to the observed prompt emission. Just after the launch of the supernova shock, a wind heated by neutrinos is driven from the protomagnetar. The outflow is collimated into a bipolar jet by its interaction with the progenitor star. As the magnetar cools, the wind becomes ultrarelativistic and Poynting flux dominated (σ0≫ 1) on a time‐scale comparable to that required for the jet to clear a cavity through the star. Although the site and mechanism of the prompt emission are debated, we calculate the emission predicted by two models: magnetic dissipation and shocks. Magnetic reconnection may occur near the photosphere if the outflow develops an alternating field structure due to e.g. magnetic instabilities or a misalignment between the magnetic and rotation axes. Shocks may occur at larger radii because the Lorentz factor of the wind increases with time, such that the faster jet at late times collides with slower material released earlier. Our results favour magnetic dissipation as the prompt emission mechanism, in part because it predicts a relatively constant ‘Band’ spectral peak energy Epeak with time during the GRB. The baryon loading of the jet decreases abruptly when the neutron star becomes transparent to neutrinos at s. Jets with ultrahigh magnetization cannot effectively accelerate and dissipate their energy, which suggests this transition ends the prompt emission. This correspondence may explain both the typical durations of long GRBs and the steep decay phase that follows. Residual rotational or magnetic energy may continue to power late time flaring or afterglow emission, such as the X‐ray plateau. We quantify the emission predicted from protomagnetars with a wide range of physical properties (initial rotation period, surface dipole field strength and magnetic obliquity) and assess a variety of phenomena potentially related to magnetar birth, including low‐luminosity GRBs, very luminous GRBs, thermal‐rich GRBs/X‐ray flashes, very luminous supernovae and short‐duration GRBs with extended emission.

Star formation is slow, in the sense that the gas consumption time is much longer than the dynamical time. It is also inefficient; essentially all star formation in local galaxies takes place in giant molecular clouds (GMCs), but the fraction of a GMC converted to stars is very small, ∼ 5%. While there is some disagreement over the lifespan of GMCs, there is a consensus that it is no more than a few cloud dynamical times. In the most luminous starbursts, the GMC lifetime is shorter than the main sequence lifetime of even the most massive stars, so that supernovae can play no role in GMC disruption; another feedback mechanism must dominate. We investigate the disruption of GMCs across a wide range of galaxies, from normal spirals to the densest starbursts; we take into account the effects of HII gas pressure, shocked stellar winds, protostellar jets, and radiation pressure produced by the absorption and scattering of starlight on dust grains. In the Milky Way, we find that a combination of three mechanisms -jets, HII gas pressure, and radiation pressure -disrupts the clouds. In more rapidly star forming galaxies such as "clump" galaxies at high-redshift, ultra-luminous infrared galaxies (ULIRGs) and submillimeter galaxies, radiation pressure dominates natal cloud distribution. We predict the presence of ∼ 10 − 20 clusters with masses ∼ 10 7 M ⊙ in local ULIRGs such as Arp 220 and a similar number of clusters with M * ∼ 10 8 M ⊙ in high redshift clump galaxies; submillimeter galaxies will have even more massive clusters. We find that the mass fraction of a GMC that ends up in stars is an increasing function of the gas surface density of a galaxy, reaching ∼ 35% in the most luminous starbursts. Furthermore, the disruption of bubbles by radiation pressure stirs the interstellar medium to velocities of ∼ 10 km s −1 in normal galaxies and to ∼ 100 km s −1 in ULIRGs like Arp 220, consistent with observations. Thus, radiation pressure may play a dominant role in the ISM of star-forming galaxies.Remarkably, equation (1) holds for galaxies like the Milky Way, with rather modest star formation rates of order a solar mass per year, for starburst galaxies with star formation