Rubin-LSST

Abstract:

Abstract We investigate the clustering of Lyman-break galaxies at redshifts of 3 ≲ z ≲ 5 within the COSMOS field by measuring the angular two-point correlation function. Our robust sample of ~60,000 bright (mUV ≲ 27) Lyman-break galaxies was selected based on spectral energy distribution fitting across 14 photometric bands spanning optical and near-infrared wavelengths. We constrained both the 1- and 2-halo terms at separations up to 300 arcsec, finding an excess in the correlation function at scales corresponding to <20 kpc, consistent with enhancement due to clumps in the same galaxy or interactions on this scale. We then performed Bayesian model fits on the correlation functions to infer the Halo Occupation Distribution parameters, star formation duty cycle, and galaxy bias in three redshift bins. We examined several cases where different combinations of parameters were varied, showing that our data can constrain the slope of the satellite occupation function, which previous studies have fixed. For an MUV-limited sub-sample, we found galaxy bias values of $b_g=3.18^{+0.14}_{-0.14}$ at z ≃ 3, $b_g=3.58^{+0.27}_{-0.29}$ at z ≃ 4, $b_g=4.27^{+0.25}_{-0.26}$ at z ≃ 5. The duty cycle values are $0.62^{+0.25}_{-0.26}$, $0.40^{+0.34}_{-0.22}$, and $0.39^{+0.31}_{-0.20}$,respectively. These results suggest that, as the redshift increases, there is a slight decrease in the host halo masses and a shorter timescale for star formation in bright galaxies, at a fixed rest-frame UV luminosity threshold.

Abstract:

Abstract Using deep observations across three of the LOFAR Two-metre Sky Survey Deep Fields, this work measures the angular clustering of star forming galaxies (SFGs) and low-excitation radio galaxies (LERGs) to z ≲1.5 for faint sources, S144 MHz ≥200 μJy. We measure the angular auto-correlation of LOFAR sources in redshift bins and their cross-correlation with multi-wavelength sources to measure the evolving galaxy bias for SFGs and LERGs. Our work shows the bias of the radio-selected SFGs increases from $b=0.90^{+0.11}_{-0.10}$ at z ∼0.2 to $b=2.94^{+0.36}_{-0.36}$ at z ∼1.2; faster than the assumed b($z$)∝1/D($z$) models adopted in previous LOFAR cosmology studies (at sensitivities where AGN dominate), but in broad agreement with previous work. We further study the luminosity dependence of bias for SFGs and find little evidence for any luminosity dependence at fixed redshift, although uncertainties remain large for the sample sizes available. The LERG population instead shows a weaker redshift evolution with $b=2.33^{+0.28}_{-0.27}$ at z ∼0.7 to $b=2.65^{+0.57}_{-0.55}$ at z ∼1.2, though it is also consistent with the assumed bias evolution model (b($z$)∝1/D($z$)) within the measured uncertainties. For those LERGs which reside in quiescent galaxies (QLERGs), there is weak evidence that they are more biased than the general LERG population and evolve from b=$2.62^{+0.33}_{-0.33}$ at z ∼0.7 to $b=3.08^{+0.85}_{-0.84}$ at z ∼1.2. This suggests the halo environment of radio sources may be related to their properties. These measurements can help constrain models for the bias evolution of these source populations, and can help inform multi-tracer analyses.

Abstract:

Abstract Astrophysical jets signpost the most extreme phenomena in the Universe. Despite a century of study, connections between the physics of black holes and the processes underpinning the formation and launch of these jets remain elusive. Here we present a statistically significant sample of transient jet speeds from stellar-mass black holes and neutron stars. The fastest jets are exclusively from black holes and propagate along a fixed axis across several ejection phases. This provides strong evidence that the most relativistic jets propagate along the spin axis of the black hole that launches them. However, we find no correlation between reported spin estimates and the jet speeds, indicating that some issues remain in connecting the theories of jet formation with spin measurements. By contrast, slower jets can be launched by both black holes and neutron stars and can change in direction or precess, indicating that they are launched from the accretion flow.

Abstract:

Abstract Using the Dark Energy Survey 5-year sample, we determine the properties of type Ia supernova (SN Ia) host galaxies across a wide multi-wavelength range – from the optical to far-infrared – including data from the Herschel and Spitzer space telescopes. We categorise the SNe Ia into three distinct groups according to the distribution of their host galaxies on the star-formation rate (SFR) – stellar mass (M⋆) plane. Each region comprises host galaxies at distinct stages in their evolutionary pathways: Region 1 – low-mass hosts; Region 2 – high-mass, star-forming hosts and Region 3 – high-mass, passive hosts. We find SNe Ia in host galaxies located in Region 1 have the steepest slope (quantified by β) between their colours and luminosities, with $\beta _{\mathrm{R_1}} = 3.51 \pm 0.16$. This differs at the ∼6σ significance level to SNe Ia in Region 3, which have the shallowest colour–luminosity slope with $\beta _{\mathrm{R_3}} = 2.12 \pm 0.16$. After correcting SNe Ia in each subsample by their respective β, events in Region 3 (high-mass, passive hosts) are 0.07 − 0.12 mag (>3σ) brighter, post-standardisation. We conclude that future cosmological analyses should apply standardisation relations to SNe Ia based upon the region in which the SN host galaxy lies in the SFR–M⋆ plane. Alternatively, cosmological analyses should restrict the SN Ia sample to events whose host galaxies occupy a single region of this plane.

Abstract:

This Letter reports the first evidence of electroweak production of same-sign $W$ boson pairs where at least one of the $W$ bosons is longitudinally polarized and the most stringent constraint to date for the production of two longitudinally polarized same-sign $W$ bosons. The dataset used corresponds to an integrated luminosity of $140{\mathrm{fb}}^{-1}$ of proton-proton collisions at a center-of-mass energy of 13 TeV, collected with the ATLAS detector during run 2 of the Large Hadron Collider. The study is performed in final states including two same-sign leptons (electrons or muons), missing transverse momentum, and at least two jets with a large invariant mass and a large rapidity difference. Two independent fits are performed targeting the production of same-sign $W$ bosons with at least one, or two longitudinally polarized $W$ bosons. The observed (expected) significance of the production with at least one longitudinally polarized $W$ boson is 3.3 (4.0) standard deviations. An observed (expected) 95% confidence level upper limit of 0.45 (0.70) fb is reported on the fiducial production cross section of two longitudinally polarized same-sign $W$ bosons.