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1. The intrinsic reddening of the Magellanic Clouds as traced by background galaxies – III. The Large Magellanic Cloud

   https://doi.org/10.1093/mnras/stac1545  

   Bell, Cameron P; Cioni, Maria-Rosa L; Wright, Angus H; Nidever, David L; Chiang, I-Da; Choudhury, Samyaday; Groenewegen, Martin A; Pennock, Clara M; Choi, Yumi; de Grijs, Richard; et al (June 2021, Monthly Notices of the Royal Astronomical Society)

   We present a map of the total intrinsic reddening across ≃ 90 deg2 of the Large Magellanic Cloud (LMC) derived using optical (ugriz) and near-infrared (IR; YJKs) spectral energy distributions (SEDs) of background galaxies. The reddening map is created from a sample of 222,752 early-type galaxies based on the lephare χ2 minimization SED-fitting routine. We find excellent agreement between the regions of enhanced intrinsic reddening across the central (4 × 4 deg2) region of the LMC and the morphology of the low-level pervasive dust emission as traced by far-IR emission. In addition, we are able to distinguish smaller, isolated enhancements that are coincident with known star-forming regions and the clustering of young stars observed in morphology maps. The level of reddening associated with the molecular ridge south of 30 Doradus is, however, smaller than in the literature reddening maps. The reduced number of galaxies detected in this region, due to high extinction and crowding, may bias our results towards lower reddening values. Our map is consistent with maps derived from red clump stars and from the analysis of the star formation history across the LMC. This study represents one of the first large-scale categorisations of extragalactic sources behind the LMC and as such we provide the lephare outputs for our full sample of ∼ 2.5 million sources. 

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2. Accretion history of AGN: Estimating the host galaxy properties in X-ray luminous AGN from z = 0–3

   https://doi.org/10.1093/mnras/stac1679  

   Coleman, Brandon; Kirkpatrick, Allison; Cooke, Kevin C.; Glikman, Eilat; La Massa, Stephanie; Marchesi, Stefano; Peca, Alessandro; Treister, Ezequiel; Auge, Connor; Urry, C. Megan; et al (June 2022, Monthly Notices of the Royal Astronomical Society)

   ABSTRACT We aim to determine the intrinsic far-Infrared (far-IR) emission of X-ray-luminous quasars over cosmic time. Using a 16 deg2 region of the Stripe 82 field surveyed by XMM-Newton and Herschel Space Observatory, we identify 2905 X-ray luminous (LX > 1042 erg/s) active galactic nuclei (AGN) in the range z ≈ 0–3. The IR is necessary to constrain host galaxy properties such as star formation rate (SFR) and gas mass. However, only 10 per cent of our AGN are detected both in the X-ray and IR. Because 90 per cent of the sample is undetected in the far-IR by Herschel, we explore the mean IR emission of these undetected sources by stacking their Herschel/SPIRE images in bins of X-ray luminosity and redshift. We create stacked spectral energy distributions from the optical to the far-IR, and estimate the median SFR, dust mass, stellar mass, and infrared luminosity using a fitting routine. We find that the stacked sources on average have similar SFR/Lbol ratios as IR detected sources. The majority of our sources fall on or above the main sequence line suggesting that X-ray selection alone does not predict the location of a galaxy on the main sequence. We also find that the gas depletion time scales of our AGN are similar to those of dusty star forming galaxies. This suggests that X-ray selected AGN host high star formation and that there are no signs of declining star formation. 

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3. Kinematical Analysis of Substructure in the Southern Periphery of the Large Magellanic Cloud

   https://doi.org/10.3847/1538-4357/ac5621  

   Cheng, Xinlun; Choi, Yumi; Olsen, Knut; Nidever, David L.; Majewski, Steven R.; Monachesi, Antonela; Besla, Gurtina; Muñoz Gonzalez, César; Anguiano, Borja; Almeida, Andres; et al (March 2022, The Astrophysical Journal)

   Abstract We report the first 3D kinematical measurements of 88 stars in the direction of several recently discovered substructures in the southern periphery of the Large Magellanic Cloud (LMC) using a combination of Gaia proper motions and radial velocities from the APOGEE-2 survey. More specifically, we explore stars in assorted APOGEE-2 pointings in a region of the LMC periphery where various overdensities of stars have previously been identified in maps of stars from Gaia and DECam. By using a model of the LMC disk rotation, we find that a sizable fraction of the APOGEE-2 stars have extreme space velocities that are distinct from, and not a simple extension of, the LMC disk. Using N -body hydrodynamical simulations of the past dynamical evolution and interaction of the LMC and Small Magellanic Cloud (SMC), we explore whether the extreme-velocity stars may be accounted for as tidal debris created in the course of that interaction. We conclude that the combination of LMC and SMC debris produced from their interaction is a promising explanation, although we cannot rule out other possible origins, and that these new data should be used to constrain future simulations of the LMC–SMC interaction. We also conclude that many of the stars in the southern periphery of the LMC lie outside of the LMC plane by several kiloparsecs. Given that the metallicity of these stars suggests that they are likely of Magellanic origin, our results suggest that a wider exploration of the past interaction history of the Magellanic Clouds is needed. 

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4. Revisiting the Classics: On the Optical Colours of Novae as Standard Crayons

   https://doi.org/10.1093/mnras/staf385  

   Craig, Peter; Aydi, Elias; Chomiuk, Laura; Strader, Jay; Stone, Ashley; Sokolovsky, Kirill V; Mukai, Koji; Kawash, Adam; Fló, Joan Guarro; Boussin, Christophe; et al (March 2025, Monthly Notices of the Royal Astronomical Society)

   Abstract We present a systematic study of the BVRI colours of novae over the course of their eruptions. Where possible, interstellar reddening was measured using the equivalent widths of Diffuse Interstellar Bands (DIBs). Some novae lack spectra with sufficient resolution and signal-to-noise ratios; therefore, we supplement as necessary with 3D and 2D dust maps. Utilising only novae with DIB- or 3D-map-based E(B − V), we find an average intrinsic (B − V)0 colour of novae at V-band light curve peak of 0.20 with a standard deviation of 0.31, based on 25 novae. When the light curve has declined by 2 magnitudes (t2), we find an average (B − V)0 = −0.03 with a standard deviation of 0.19. These average colours are consistent with previous findings, although the spreads are larger than previously found due to more accurate reddening estimates. We also examined the intrinsic (R − I)0 and (V − R)0 colours across our sample. These colours behave similarly to (B − V)0, except that the (V − R)0 colour gets redder after peak, likely due to the contributions of emission line flux. We searched for correlations between nova colours and t2, peak V-band absolute magnitude, and GeV γ-ray luminosity, but find no statistically significant correlations. Nova colours can therefore be used as standard “crayons” to estimate interstellar reddening from photometry alone, with 0.2–0.3 mag uncertainty. We present a novel Bayesian strategy for estimating distances to Galactic novae based on these E(B − V) measurements, independent of assumptions about luminosity, built using 3D dust maps and a stellar mass model of the Milky Way. 

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5. Using Very Large Array Data to Image the Ultra-Diffuse Galaxy AGC 749251

   Reiter, Kameron; Leisman, Lukas (January 2019, American Astronomical Society, AAS Meeting)

   Ultra-diffuse galaxies (UDGs) have generated significant interest in recent years, as their stars appear too spread out relative to typical galaxies, and because some UDGs appear to have more than typical amounts of dark matter. The ALFALFA Survey has detected a number of UDGs in the field that are rich with neutral hydrogen (HI). We use the Karl G. Jansky Very Large Array (VLA) to image one of these HI-rich UDG, AGC 749251. We manually remove radio frequency interference, and reduce it using standard procedures in CASA. From the resulting data cubes we created 2D maps (moment 0 maps) and maps of the radial velocities of the HI gas. We find that the HI in AGC 749251 shows reasonably ordered morphology and rotation, and extends beyond the already extended optical emission. We estimate the source's inclination and rotation velocity, constraining the source's dark matter content. We also compare our results to other, non-ultra diffuse galaxies, and suggest that the rotation velocity seems low compared with other sources of similar mass. This work has been supported by NSF grant AST-1637339. 

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