Rubin-LSST

Abstract:

Over the past decade, several works have used the ratio between total (rest 8−1000 μm) infrared and radio (rest 1.4 GHz) luminosity in star-forming galaxies (qIR), often referred to as the infrared-radio correlation (IRRC), to calibrate the radio emission as a star formation rate (SFR) indicator. Previous studies constrained the evolution of qIR with redshift, finding a mild but significant decline that is yet to be understood. Here, for the first time, we calibrate qIR as a function of both stellar mass (M⋆) and redshift, starting from an M⋆-selected sample of > 400 000 star-forming galaxies in the COSMOS field, identified via (NUV − r)/(r − J) colours, at redshifts of 0.1 < z < 4.5. Within each (M⋆,z) bin, we stacked the deepest available infrared/sub-mm and radio images. We fit the stacked IR spectral energy distributions with typical star-forming galaxy and IR-AGN templates. We then carefully removed the radio AGN candidates via a recursive approach. We find that the IRRC evolves primarily with M⋆, with more massive galaxies displaying a systematically lower qIR. A secondary, weaker dependence on redshift is also observed. The best-fit analytical expression is the following: qIR(M⋆, z) = (2.646 ± 0.024) × (1 + z)( − 0.023 ± 0.008)–(0.148 ± 0.013) × (log M⋆/M⊙ − 10). Adding the UV dust-uncorrected contribution to the IR as a proxy for the total SFR would further steepen the qIR dependence on M⋆. We interpret the apparent redshift decline reported in previous works as due to low-M⋆ galaxies being progressively under-represented at high redshift, as a consequence of binning only in redshift and using either infrared or radio-detected samples. The lower IR/radio ratios seen in more massive galaxies are well described by their higher observed SFR surface densities. Our findings highlight the fact that using radio-synchrotron emission as a proxy for SFR requires novel M⋆-dependent recipes that will enable us to convert detections from future ultra-deep radio surveys into accurate SFR measurements down to low-M⋆ galaxies with low SFR.

Abstract:

The next core-collapse supernova in the Milky Way or its satellites will represent a once-in-a-generation opportunity to obtain detailed information about the explosion of a star and provide significant scientific insight for a variety of fields because of the extreme conditions found within. Supernovae in our galaxy are not only rare on a human timescale but also happen at unscheduled times, so it is crucial to be ready and use all available instruments to capture all possible information from the event. The first indication of a potential stellar explosion will be the arrival of a bright burst of neutrinos. Its observation by multiple detectors worldwide can provide an early warning for the subsequent electromagnetic fireworks, as well as signal to other detectors with significant backgrounds so they can store their recent data. The supernova early warning system (SNEWS) has been operating as a simple coincidence between neutrino experiments in automated mode since 2005. In the current era of multi-messenger astronomy there are new opportunities for SNEWS to optimize sensitivity to science from the next galactic supernova beyond the simple early alert. This document is the product of a workshop in June 2019 towards design of SNEWS 2.0, an upgraded SNEWS with enhanced capabilities exploiting the unique advantages of prompt neutrino detection to maximize the science gained from such a valuable event.