Rubin-LSST

Abstract:

Fast radio bursts (FRBs) probe baryons permeating the cosmic web through their dispersion measures (DMs), which encode the integrated electron density along cosmological sight lines. Using 3455 unique FRB sources from CHIME/FRB with ∼15′ localizations, we present an anthology of DM correlations with tracers of large-scale structure and baryonic matter at redshifts z ≲ 1.5. We measured correlations with a vector signal-to-noise ratio (SNR) of 2.4–5 with 10 probes, including galaxies (2.8), weak gravitational lensing (2.6), cosmic infrared background (4.0), cosmic microwave background (CMB) lensing (3.3), the thermal Sunyaev–Zel’dovich (tSZ) effect (3.8), X-ray emission tracing galaxy clusters (5.0) and superclusters (3.3), soft X-ray background (SXRB, 4.1), and radio continuum emission (3.0). These measurements reveal a consistent picture in which FRB sight lines intersecting overdense environments carry systematically larger DMs. Correlations with hot-gas tracers provide additional leverage on the strength of feedback, as they are strongly weighted toward the dense, bound gas. The measured amplitude of tSZ×DM and SXRB×DM correlations is consistent with theoretical predictions of baryon distribution from a DM–z relation-inferred model with moderate feedback at a ∼0.5σ level. A weaker feedback scenario is disfavored at ∼3.5σ by the SXRB×DM correlation under our adopted modeling assumptions. Taken together, these measurements constitute a quantitative multitracer foundation for a new era in which FRBs from next-generation facilities, such as BURSTT, CHORD, the Deep Synoptic Array, and the Square Kilometer Array, in harmony with other probes, will map the baryon content of the full extent of the cosmic web.

Abstract:

In the coming years, the Vera Rubin Observatory’s Legacy Survey of Space and Time (Rubin-LSST) and the Nancy Grace Roman Space Telescope’s (Roman) High Latitude Time Domain Survey (HLTDS) are expected to discover more than a million Type Ia supernovae (SNe Ia), several orders of magnitude more than current samples and with a tighter control on systematic uncertainties. One of the largest systematic uncertainties in cosmological analyses with SNe Ia is the accuracy of the spectrophotometric model for SNe Ia time series data, which depends on the photometric calibration of the surveys. To quantify the impact of this uncertainty, we analyze simulated Rubin-LSST and HLTDS data, perturb the photometric zero-points and filter mean wavelengths, and propagate these systematics to spectral model recovery, estimated distances, and dark energy Figure of Merit (FoM) based on the w0waCDM model. Zero-point shifts of 5 mmag and filter mean wavelength shifts of 5 Å lead to a ∼50% decrease in the FoM relative to a statistical-only case when calibration uncertainties are propagated only through light-curve fitting. The same calibration shifts applied only during model training produce a smaller ∼13% degradation. Contrary to previous analyses, calibration uncertainties in light-curve fitting dominate over those from model training. Their effect during light-curve fitting varies smoothly with redshift and is nearly degenerate with cosmology, preventing mitigation through self-calibration. Finally, we show that the FoM dependence on the size of the calibration uncertainties (in the range of expected sizes) is roughly linear.

Abstract:

Abstract Cosmic filaments have been recognised as influencing galaxy evolution, but their connection to galactic cold gas reservoirs is elusive, particularly at low redshifts. We investigate the influence of filaments on neutral hydrogen (H i) detections in galaxies at 0.02 < z < 0.09, using the MeerKAT International GHz Tiered Extragalactic Exploration (MIGHTEE) survey in the COSMOS and XMM-LSS fields. We measure the fraction of optical galaxies from the Dark Energy Spectroscopic Instrument (DESI) Survey detected in H i emission as a function of stellar mass, morphology, local density, and the distance to the nearest filament. We find that galaxies closer to filaments have higher stellar masses, higher local densities, and a larger early-type fraction, all of which affect the H i detection. After controlling for these dependencies, filaments have measurable effects on H i detection. Late-type galaxies in low-local density environments show reduced H i detection fractions close to filaments across all stellar mass ranges, suggesting potential gas depletion through ram pressure stripping and cosmic web detachment. Massive early-type galaxies show an enhanced H i detection fraction in filaments compared to the voids, suggesting possible gas replenishment through filamentary accretion or gas-rich mergers. Our results suggest that cosmic filaments influence galactic H i gas reservoirs through various competing processes, whose relative importance varies with stellar mass and local density.

Abstract:

This research note presents a new planet candidate orbiting the K-dwarf TIC 392664683, which was discovered by citizen scientists as part of the Planet Hunter TESS (PHT) project. Three transit-like events were observed in Sectors 38, 65 and 102; the available data imply that the orbital period must be either 23 or 46 days. The transit depth of 1964−212+433 ppm and duration of 5.4−0.2+0.4 hr are consistent across the three sectors spanning almost five years of TESS data. Using a stellar radius of 0.7740 ± 0.0168R⊙ we derive a planetary radius between 3.5 and 4.2 R⊕, approximately the same as Neptune. Comprehensive vetting mitigates the risk that this is a false positive and supports the candidate’s likely planetary nature.