Rubin-LSST

Abstract:

A measurement is presented of elliptic ( $v_2$ ) and triangular ( $v_3$ ) azimuthal anisotropy coefficients for charged particles produced in $\mathrm{Pb}+\mathrm{Pb}$ collisions at $\sqrt{s_{{}_{\text{NN}}}}=5.02 \text{TeV}$ using a dataset corresponding to an integrated luminosity of $0.44{\text{nb}}^{-1}$ collected with the ATLAS detector at the LHC in 2018. The values of $v_2$ and $v_3$ are measured for charged particles over a wide range of transverse momentum ( $p_{\text{T}}$ ), 1–400 $\text{GeV}$ , and $\mathrm{Pb}+\mathrm{Pb}$ collision centrality, 0–60%, using the scalar-product and multiparticle cumulant methods. These methods are sensitive to event-by-event fluctuations and nonflow effects in the measurements of azimuthal anisotropies. Positive values of $v_2$ are observed up to a $p_{\text{T}}$ of approximately 100 $\text{GeV}$ from both methods across all centrality intervals. Positive values of $v_3$ are observed up to approximately 25 $\text{GeV}$ using both methods, though the application of the three-subevent technique to the multiparticle cumulant method leads to significant changes at the highest $p_{\text{T}}$ . At high $p_{\text{T}}$ ( $p_{\text{T}}⪆10 \text{GeV}$ ), charged particles are dominantly from jet fragmentation. These jets, and hence the measurements presented here, are sensitive to the path-length dependence of parton energy loss in the quark-gluon plasma produced in $\mathrm{Pb}+\mathrm{Pb}$ collisions.

Abstract:

We present the photometric and spectroscopic analysis of five Type Ibn supernovae (SNe): SN 2020nxt, SN 2020taz, SN 2021bbv, SN 2023utc, and SN 2024aej. These events share key observational features and belong to a family of objects similar to the prototypical Type Ibn SN 2006jc. The SNe exhibit rise times of approximately 10 days and peak absolute magnitudes ranging from −16.5 to −19 mag. Notably, SN 2023utc is the faintest Type Ibn SN discovered to date, with an exceptionally low r -band absolute magnitude of −16.4 mag. The pseudo-bolometric light curves peak at (1 − 10)×10 42 erg s −1 , with total radiated energies on the order of (1 − 10)×10 48 erg. Spectroscopically, these SNe display a relatively slow spectral evolution. The early spectra are characterised by a hot blue continuum and prominent He  I emission lines. The early spectra also show blackbody temperatures exceeding 10 000 K, with a subsequent decline in temperature during later phases. Narrow He  I lines, which are indicative of unshocked circumstellar material (CSM), show velocities of approximately 1000 km s −1 . The spectra suggest that the progenitors of these SNe underwent significant mass loss prior to the explosion, resulting in a He-rich CSM. Our light curve modelling yielded estimates for the ejecta mass ( M ej ) in the range 1 − 3 M ⊙ with kinetic energies ( E Kin ) of (0.1 − 1)×10 50 erg. The inferred CSM mass ranges from 0.2 to 1 M ⊙ . These findings are consistent with expectations for core collapse events arising from relatively massive envelope-stripped progenitors.

Abstract:

We present new K -band spectroscopy for the giant elliptical galaxy M87 in the Virgo cluster, taken with the Large Binocular Telescope Utility Camera in the Infrared (LUCI) spectrograph at the Large Binocular Telescope (LBT). The new data are used to study line strengths of K -band absorption features from different chemical species, namely Fe, Mg, Ca, Na, and CO, as a function of galactocentric distance, out to ∼40″ from the center (about half of the galaxy effective radius). The radial trends of spectral indices are compared to those for the bulge of M31, observed with the same instrument. For M87, most K -band indices exhibit flat radial profiles, with the exception of NaI2.21, which decreases outward, with a negative radial gradient. Significant offsets are found between indices for M87 and those for the bulge of M31, the latter having weaker line strengths for almost all features, but Fe and Ca, for which we find similar trends in both systems. We find that the behavior of CO features – most prominent in giant stars – is difficult to explain, consistent with previous results for the central regions of massive galaxies. In particular, the CO indices are stronger in M87 than M31, and do not exhibit significant radial gradients in M87, despite its IMF being bottom heavier than M31 especially in its central region. Predictions of state-of-the-art stellar population models, based on results from the optical spectral range, are able to match only the Na and Ca indices of M87, while a significant mismatch is found for all other indices. This shows that state-of-the-art stellar population models should be improved significantly in order to provide reliable constraints on the stellar population content of galaxies in the near-infrared spectral range.