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- ItemA Highly Magnified Gravitationally Lensed Red QSO at z = 2.5 with a Significant Flux Ratio Anomaly(London : Institute of Physics Publ., 2023) Glikman, Eilat; Rusu, Cristian E.; Chen, Geoff C.-F.; Chan, James Hung-Hsu; Spingola, Cristiana; Stacey, Hannah; McKean, John; Berghea, Ciprian T.; Djorgovski, S. G.; Graham, Matthew J.; Stern, Daniel; Urrutia, Tanya; Lacy, Mark; Secrest, Nathan J.; O’Meara, John M.We present the discovery of a gravitationally lensed dust-reddened QSO at z = 2.517, identified in a survey for QSOs by infrared selection. Hubble Space Telescope imaging reveals a quadruply lensed system in a cusp configuration, with a maximum image separation of ∼1.″8. We find that, compared to the central image of the cusp, the neighboring brightest image is anomalous by a factor of ∼7-10, which is the largest flux anomaly measured to date in a lensed QSO. Incorporating high-resolution Very Large Array radio imaging and submillimeter imaging with the Atacama Large Millimeter/submillimeter Array, we conclude that a low-mass perturber is the most likely explanation for the anomaly. The optical through near-infrared spectrum reveals that the QSO is moderately reddened with E(B − V) ≃ 0.7-0.9. We see an upturn in the ultraviolet spectrum due to ∼1% of the intrinsic emission being leaked back into the line of sight, which suggests that the reddening is intrinsic and not due to the lens. The QSO may have an Eddington ratio as high as L/L Edd ≈ 0.2. Consistent with previous red QSO samples, this source exhibits outflows in its spectrum, as well as morphological properties suggestive of it being in a merger-driven transitional phase. We find a host galaxy stellar mass of log M ⋆ / M ⊙ = 11.4 , which is higher than the local M BH versus M ⋆ relation but consistent with other high-redshift QSOs. When demagnified, this QSO is at the knee of the luminosity function, allowing for the detailed study of a more typical moderate-luminosity infrared-selected QSO at high redshift.
- ItemThe Bimodal Absorption System Imaging Campaign (BASIC). I. A Dual Population of Low-metallicity Absorbers at z < 1(London : Institute of Physics Publ., 2023) Berg, Michelle A.; Lehner, Nicolas; Howk, J. Christopher; O’Meara, John M.; Schaye, Joop; Straka, Lorrie A.; Cooksey, Kathy L.; Tripp, Todd M.; Prochaska, J. Xavier; Oppenheimer, Benjamin D.; Johnson, Sean D.; Muzahid, Sowgat; Bordoloi, Rongmon; Werk, Jessica K.; Fox, Andrew J.; Katz, Neal; Wendt, Martin; Peeples, Molly S.; Ribaudo, Joseph; Tumlinson, JasonThe bimodal absorption system imaging campaign (BASIC) aims to characterize the galaxy environments of a sample of 36 H i-selected partial Lyman limit systems (pLLSs) and Lyman limit systems (LLSs) in 23 QSO fields at z ≲ 1. These pLLSs/LLSs provide a unique sample of absorbers with unbiased and well-constrained metallicities, allowing us to explore the origins of metal-rich and low-metallicity circumgalactic medium (CGM) at z < 1. Here we present Keck/KCWI and Very Large Telescope/MUSE observations of 11 of these QSO fields (19 pLLSs) that we combine with Hubble Space Telescope/Advanced Camera for Surveys imaging to identify and characterize the absorber-associated galaxies at 0.16 ≲ z ≲ 0.84. We find 23 unique absorber-associated galaxies, with an average of one associated galaxy per absorber. For seven absorbers, all with <10% solar metallicities, we find no associated galaxies with log M ⋆ ≳ 9.0 within ρ/R vir and ∣Δv∣/v esc ≤ 1.5 with respect to the absorber. We do not find any strong correlations between the metallicities or H i column densities of the gas and most of the galaxy properties, except for the stellar mass of the galaxies: the low-metallicity ([X/H] ≤ −1.4) systems have a probability of 0.39 − 0.15 + 0.16 for having a host galaxy with log M ⋆ ≥ 9.0 within ρ/R vir ≤ 1.5, while the higher metallicity absorbers have a probability of 0.78 − 0.13 + 0.10 . This implies metal-enriched pLLSs/LLSs at z < 1 are typically associated with the CGM of galaxies with log M ⋆ > 9.0 , whereas low-metallicity pLLSs/LLSs are found in more diverse locations, with one population arising in the CGM of galaxies and another more broadly distributed in overdense regions of the universe. Using absorbers not associated with galaxies, we estimate the unweighted geometric mean metallicity of the intergalactic medium to be [X/H] ≲ −2.1 at z < 1, which is lower than previously estimated.
- ItemErratum: "On the Use of Field RR Lyrae as Galactic Probes. V. Optical and Radial Velocity Curve Templates" (2021, ApJ, 919, 85)(London : Institute of Physics Publ., 2023) Braga, V.F.; Crestani, J.; Fabrizio, M.; Bono, G.; Sneden, C.; Preston, G.W.; Storm, J.; Kamann, S.; Latour, M.; Lala, H.; Lemasle, B.; Prudil, Z.; Altavilla, G.; Chaboyer, B.; Dall’Ora, M.; Ferraro, I.; Gilligan, C.K.; Fiorentino, G.; Iannicola, G.; Inno, L.; Kwak, S.; Marengo, M.; Marinoni, S.; Marrese, P.M.; Martínez-Vázquez, C.E.; Monelli, M.; Mullen, J.P.; Matsunaga, N.; Neeley, J.; Stetson, P.B.; Valenti, E.; Zoccali, M.[no abstract available]
- ItemPegasus IV: Discovery and Spectroscopic Confirmation of an Ultra-faint Dwarf Galaxy in the Constellation Pegasus(London : Institute of Physics Publ., 2023) Cerny, W.; Simon, J.D.; Li, T.S.; Drlica-Wagner, A.; Pace, A.B.; Martínez-Vázquez, C.E.; Riley, A.H.; Mutlu-Pakdil, B.; Mau, S.; Ferguson, P.S.; Erkal, D.; Munoz, R.R.; Bom, C.R.; Carlin, J.L.; Carollo, D.; Choi, Y.; Ji, A.P.; Manwadkar, V.; Martínez-Delgado, D.; Miller, A.E.; Noël, N.E.D.; Sakowska, J.D.; Sand, D.J.; Stringfellow, G.S.; Tollerud, E.J.; Vivas, A.K.; Carballo-Bello, J.A.; Hernandez-Lang, D.; James, D.J.; Nidever, D.L.; Nilo Castellon, J.L.; Olsen, K.A.G.; Zenteno, A.We report the discovery of Pegasus IV, an ultra-faint dwarf galaxy found in archival data from the Dark Energy Camera processed by the DECam Local Volume Exploration Survey. Pegasus IV is a compact, ultra-faint stellar system (r1 2 = 41-+68 pc; MV = −4.25 ± 0.2 mag) located at a heliocentric distance of 90-+64 kpc. Based on spectra of seven nonvariable member stars observed with Magellan/IMACS, we confidently resolve Pegasus IV’s velocity dispersion, measuring sv = 3.3-+1.11.7 km s−1 (after excluding three velocity outliers); this implies a mass-to-light ratio of M1 2 LV,1 2 = 167-+99224M☉ L☉ for the system. From the five stars with the highest signal-to-noise spectra, we also measure a systemic metallicity of [Fe/H] =-2.63-+0.300.26 dex, making Pegasus IV one of the most metal-poor ultra-faint dwarfs. We tentatively resolve a nonzero metallicity dispersion for the system. These measurements provide strong evidence that Pegasus IV is a dark-matter-dominated dwarf galaxy, rather than a star cluster. We measure Pegasus IV’s proper motion using data from Gaia Early Data Release 3, finding (μα*, μδ) = (0.33 ± 0.07, −0.21 ± 0.08) mas yr−1. When combined with our measured systemic velocity, this proper motion suggests that Pegasus IV is on an elliptical, retrograde orbit, and is currently near its orbital apocenter. Lastly, we identify three potential RR Lyrae variable stars within Pegasus IV, including one candidate member located more than 10 half-light radii away from the system’s centroid. The discovery of yet another ultra-faint dwarf galaxy strongly suggests that the census of Milky Way satellites is still incomplete, even within 100 kpc.
- ItemThe Active Galactic Nuclei in the Hobby-Eberly Telescope Dark Energy Experiment Survey (HETDEX). III. A Red Quasar with Extremely High Equivalent Widths Showing Powerful Outflows(London : Institute of Physics Publ., 2022) Liu, Chenxu; Gebhardt, Karl; Kollatschny, Wolfram; Ciardullo, Robin; Mentuch Cooper, Erin; Davis, Dustin; Farrow, Daniel J.; Finkelstein, Steven L.; Gawiser, Eric; Gronwall, Caryl; Hill, Gary J.; House, Lindsay; Schneider, Donald P.; Urrutia, Tanya; Zeimann, Gregory R.We report an active galactic nucleus (AGN) with an extremely high equivalent width (EW), EWLyα+N V,rest ≳921 Å, in the rest frame, at z ∼ 2.24 in the Hobby-Eberly Telescope Dark Energy Experiment Survey (HETDEX), as a representative case of the high-EW AGN population. The continuum level is a nondetection in the HETDEX spectrum; thus the measured EW is a lower limit. The source is detected with significant emission lines (>7σ) at Lyα + N v λ1241, C iv λ1549, and a moderate emission line (∼4σ) at He ii λ1640 within the wavelength coverage of HETDEX (3500-5500 Å). The r-band magnitude is 24.57 from the Hyper Suprime-Cam-HETDEX joint survey with a detection limit of r = 25.12 at 5σ. The Lyα emission line spans a clearly resolved region of ∼10″ (85 kpc) in diameter. The Lyα line profile is strongly double peaked. The spectral decomposed blue gas and red gas Lyα emission are separated by ∼1.″2 (10.1 kpc) with a line-of-sight velocity offset of ∼1100 km s−1. This source is probably an obscured AGN with powerful winds.
- ItemStellar Energetic Particle Transport in the Turbulent and CME-disrupted Stellar Wind of AU Microscopii(London : Institute of Physics Publ., 2022) Fraschetti, Federico; Alvarado-Gómez, Julián D.; Drake, Jeremy J.; Cohen, Ofer; Garraffo, CeciliaEnergetic particles emitted by active stars are likely to propagate in astrospheric magnetized plasma and disrupted by the prior passage of energetic coronal mass ejections (CMEs). We carried out test-particle simulations of ∼GeV protons produced at a variety of distances from the M1Ve star AU Microscopii by coronal flares or traveling shocks. Particles are propagated within a large-scale quiescent three-dimensional magnetic field and stellar wind reconstructed from measured magnetograms, and within the same stellar environment following the passage of a 1036 erg kinetic energy CME. In both cases, magnetic fluctuations with an isotropic power spectrum are overlayed onto the large-scale stellar magnetic field and particle propagation out to the two innnermost confirmed planets is examined. In the quiescent case, the magnetic field concentrates the particles into two regions near the ecliptic plane. After the passage of the CME, the closed field lines remain inflated and the reshuffled magnetic field remains highly compressed, shrinking the scattering mean free path of the particles. In the direction of propagation of the CME lobes the subsequent energetic particle (EP) flux is suppressed. Even for a CME front propagating out of the ecliptic plane, the EP flux along the planetary orbits highly fluctuates and peaks at ∼2-3 orders of magnitude higher than the average solar value at Earth, both in the quiescent and the post-CME cases.
- ItemA Deep View into the Nucleus of the Sagittarius Dwarf Spheroidal Galaxy with MUSE. III. Discrete Multicomponent Population-dynamical Models Based on the Jeans Equations(London : Institute of Physics Publ., 2022) Kacharov, Nikolay; Alfaro-Cuello, Mayte; Neumayer, Nadine; Lützgendorf, Nora; Watkins, Laura L.; Mastrobuono-Battisti, Alessandra; Kamann, Sebastian; van de Ven, Glenn; Seth, Anil C.; Voggel, Karina T.; Georgiev, Iskren Y.; Leaman, Ryan; Bianchini, Paolo; Böker, Torsten; Mieske, SteffenWe present comprehensive multicomponent dynamical models of M54 (NGC 6715), the nuclear star cluster of the Sagittarius (Sgr) dwarf galaxy, which is undergoing a tidal disruption in the Milky Way halo. Previous papers in this series used a large MUSE mosaic data set to identify multiple stellar populations in the system and study their kinematic differences. Here, we use Jeans-based dynamical models that fit the population properties (mean age and metallicity), spatial distributions, and kinematics simultaneously. They provide a solid physical explanation for our previous findings. Population-dynamical models deliver a comprehensive view of the whole system, and allow us to disentangle the different stellar populations. We explore their dynamical interplay and confirm our previous findings about the build-up of Sgr’s nuclear cluster via contributions from globular cluster stars, Sgr inner field stars, and in situ star formation. We explore various parameterizations of the gravitational potential and show the importance of a radially varying mass-to-light ratio for the proper treatment of the mass profile. We find a total dynamical mass within M54's tidal radius (∼75 pc) of 1.60 ± 0.07 × 106 M ⊙ in excellent agreement with N-body simulations. Metal-poor globular cluster stars contribute about 65% of the total mass or 1.04 ± 0.05 × 106 M ⊙. Metal-rich stars can be further divided into young and intermediate-age populations, which contribute 0.32 ± 0.02 × 106 M ⊙ (20%) and 0.24 ± 0.02 × 106 M ⊙ (15%), respectively. Our population-dynamical models successfully distinguish the different stellar populations in Sgr’s nucleus because of their different spatial distributions, ages, metallicities, and kinematic features.
- ItemHETDEX Public Source Catalog 1: 220 K Sources Including Over 50 K Lyα Emitters from an Untargeted Wide-area Spectroscopic Survey(London : Institute of Physics Publ., 2023) Mentuch Cooper, Erin; Gebhardt, Karl; Davis, Dustin; Farrow, Daniel J.; Liu, Chenxu; Zeimann, Gregory; Ciardullo, Robin; Feldmeier, John J.; Drory, Niv; Jeong, Donghui; Benda, Barbara; Bowman, William P.; Boylan-Kolchin, Michael; Chávez Ortiz, Óscar A.; Debski, Maya H.; Dentler, Mona; Fabricius, Maximilian; Farooq, Rameen; Finkelstein, Steven L.; Gawiser, Eric; Gronwall, Caryl; Hill, Gary J.; Hopp, Ulrich; House, Lindsay R.; Janowiecki, Steven; Khoraminezhad, Hasti; Kollatschny, Wolfram; Komatsu, Eiichiro; Landriau, Martin; Niemeyer, Maja Lujan; Lee, Hanshin; MacQueen, Phillip; Mawatari, Ken; McKay, Brianna; Ouchi, Masami; Poppe, Jennifer; Saito, Shun; Schneider, Donald P.; Snigula, Jan; Thomas, Benjamin P.; Tuttle, Sarah; Urrutia, Tanya; Weiss, Laurel; Wisotzki, Lutz; Zhang, YechiWe present the first publicly released catalog of sources obtained from the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX). HETDEX is an integral field spectroscopic survey designed to measure the Hubble expansion parameter and angular diameter distance at 1.88 < z < 3.52 by using the spatial distribution of more than a million Lyα-emitting galaxies over a total target area of 540 deg2. The catalog comes from contiguous fiber spectra coverage of 25 deg2 of sky from 2017 January through 2020 June, where object detection is performed through two complementary detection methods: one designed to search for line emission and the other a search for continuum emission. The HETDEX public release catalog is dominated by emission-line galaxies and includes 51,863 Lyα-emitting galaxy (LAE) identifications and 123,891 [O ii]-emitting galaxies at z < 0.5. Also included in the catalog are 37,916 stars, 5274 low-redshift (z < 0.5) galaxies without emission lines, and 4976 active galactic nuclei. The catalog provides sky coordinates, redshifts, line identifications, classification information, line fluxes, [O ii] and Lyα line luminosities where applicable, and spectra for all identified sources processed by the HETDEX detection pipeline. Extensive testing demonstrates that HETDEX redshifts agree to within Δz < 0.02, 96.1% of the time to those in external spectroscopic catalogs. We measure the photometric counterpart fraction in deep ancillary Hyper Suprime-Cam imaging and find that only 55.5% of the LAE sample has an r-band continuum counterpart down to a limiting magnitude of r ∼ 26.2 mag (AB) indicating that an LAE search of similar sensitivity to HETDEX with photometric preselection would miss nearly half of the HETDEX LAE catalog sample. Data access and details about the catalog can be found online at http://hetdex.org/. A copy of the catalogs presented in this work (Version 3.2) is available to download at Zenodo doi:10.5281/zenodo.7448504.
- ItemThe Longest Delay: A 14.5 yr Campaign to Determine the Third Time Delay in the Lensing Cluster SDSS J1004+4112(London : Institute of Physics Publ., 2022) Muñoz, J.A.; Kochanek, C.S.; Fohlmeister, J.; Wambsganss, J.; Falco, E.; Forés-Toribio, R.We present new light curves for the four bright images of the five image cluster-lensed quasar gravitational lens system SDSS J1004+4112. The light curves span 14.5 yr and allow the measurement of the time delay between the trailing bright quasar image D and the leading image C. When we fit all four light curves simultaneously and combine the models using the Bayesian information criterion, we find a time delay of Δt DC = 2458.47 ± 1.02 days (6.73 yr), the longest ever measured for a gravitational lens. For the other two independent time delays we obtain Δt BC = 782.20 ± 0.43 days (2.14 yr) and Δt AC = 825.23 ± 0.46 days (2.26 yr), in agreement with previous results. The information criterion is needed to weight the results for light curve models with different polynomial orders for the intrinsic variability and the effects of differential microlensing. The results using the Akaike information criterion are slightly different, but, in practice, the absolute delay errors are all dominated by the ∼4% cosmic variance in the delays rather than the statistical or systematic measurement uncertainties. Despite the lens being a cluster, the quasar images show slow differential variability due to microlensing at the level of a few tenths of a magnitude.
- ItemUntangling the Sources of Abundance Dispersion in Low-metallicity Stars(London : Institute of Physics Publ., 2023) Griffith, Emily J.; Johnson, Jennifer A.; Weinberg, David H.; Ilyin, Ilya; Johnson, James W.; Rodriguez-Martinez, Romy; Strassmeier, Klaus G.We measure abundances of 12 elements (Na, Mg, Si, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni) in a sample of 86 metal-poor (−2 ≲ [Fe/H] ≲ −1) subgiant stars in the solar neighborhood. Abundances are derived from high-resolution spectra taken with the Potsdam Echelle Polarimetric and Spectroscopic Instrument on the Large Binocular Telescope, modeled using iSpec and MOOG. By carefully quantifying the impact of photon-noise (<0.05 dex for all elements), we robustly measure the intrinsic scatter of abundance ratios. At fixed [Fe/H], the rms intrinsic scatter in [X/Fe] ranges from 0.04 (Cr) to 0.16 dex (Na), with a median of 0.08 dex. Scatter in [X/Mg] is similar, and accounting for [α/Fe] only reduces the overall scatter moderately. We consider several possible origins of the intrinsic scatter with particular attention to fluctuations in the relative enrichment by core-collapse supernovae (CCSN) and Type Ia supernovae and stochastic sampling of the CCSN progenitor mass distribution. The stochastic sampling scenario provides a good quantitative explanation of our data if the effective number of CCSN contributing to the enrichment of a typical sample star is N ∼ 50. At the median metallicity of our sample, this interpretation implies that the CCSN ejecta are mixed over a gas mass ∼6 × 104 M ⊙ before forming stars. The scatter of elemental abundance ratios is a powerful diagnostic test for simulations of star formation, feedback, and gas mixing in the early phases of the Galaxy.