More Like this

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

   https://doi.org/10.1093/mnras/staa2786  

   Bell, Cameron P; Cioni, Maria-Rosa L; Wright, A H; Rubele, Stefano; Nidever, David L; Tatton, Ben L; van Loon, Jacco Th; Zaritsky, Dennis; Choi, Yumi; Choudhury, Samyaday; et al (October 2020, Monthly Notices of the Royal Astronomical Society)

   null (Ed.)

   ABSTRACT We present a map of the total intrinsic reddening across ≃34 deg2 of the Small Magellanic Cloud (SMC) derived using optical (ugriz) and near-infrared (IR; YJKs) spectral energy distributions (SEDs) of background galaxies. The reddening map is created using a subsample of 29 274 galaxies with low levels of intrinsic reddening based on the lephare χ2 minimization SED-fitting routine. We find statistically significant enhanced levels of reddening associated with the main body of the SMC compared with regions in the outskirts [ΔE(B − V) ≃ 0.3 mag]. A comparison with literature reddening maps of the SMC shows that, after correcting for differences in the volume of the SMC sampled, there is good agreement between our results and maps created using young stars. In contrast, we find significant discrepancies between our results and maps created using old stars or based on longer wavelength far-IR dust emission that could stem from biased samples in the former and uncertainties in the far-IR emissivity and the optical properties of the dust grains in the latter. This study represents one of the first large-scale categorizations of extragalactic sources behind the SMC and as such we provide the lephare outputs for our full sample of ∼500 000 sources. 

   more » « less
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. 

   more » « less
3. LMC+ : Large-scale mapping of [C II] and [O III] in the LMC molecular ridge: I. Dataset and line ratio analyses

   https://doi.org/10.1051/0004-6361/202555833  

   Fischer, C; Madden, S C; Krabbe, A; Polles, F L; Fadda, D; Tarantino, E; Galliano, F; Chen, C-H R; Abel, N; Beck, Á; et al (October 2025, Astronomy & Astrophysics)

   Context. The fundamental process of star formation in galaxies involves the intricate interplay between the fueling of star formation via molecular gas and the feedback from recently formed massive stars that can, in turn, hinder the conversion of gas into stars. This process, by which galaxies evolve, is also closely connected to the intrinsic properties of the interstellar medium (ISM), such as structure, density, pressure, and metallicity. Aims. To study the role that different molecular and atomic phases of the ISM play in star formation, and to characterize their physical conditions, we zoom into our nearest neighboring galaxy, the Large Magellanic Cloud (LMC; 50 kpc), the most convenient laboratory in which to study the effects of the lower metal abundance on the properties of the ISM. The LMC offers a view of the ISM and star formation conditions in a low-metallicity (Z~ 0.5 Z_⊙) environment similar, in that regard, to the epoch of the peak of star formation in the earlier Universe (z~ 1.5). Following up on studies carried out at galactic scales in low-Z galaxies, we present an unprecedentedly detailed analysis of well-known star-forming regions (SFRs) at a spatial resolution of a few parsecs. Methods. We mapped a 610pc× 260pc region in the LMC molecular ridge in [C II]λ158 µm and the [O III]λ88 µm using the FIFI-LS instrument on the SOFIA telescope. We compared the data with the distribution of the CO(2−1) emission from ALMA, the modeled total infrared luminosity, and the Spitzer/MIPS 24 µm continuum and Hα. Results. We present new large maps of [CII] and [OIII] and perform a first comparison with CO(2−1) line and LTIR emission. We also provide a detailed description of the observing strategy with SOFIA/FIFI-LS and the data reduction process. Conclusions. We find that [CII] and [OIII] emission is associated with the SFRs in the molecular ridge, but also extends throughout the mapped region, and is not obviously associated with ongoing star formation. The CO emission is clumpier than the [C II] emission and we find plentiful [C II] present where there is little CO emission, possibly holding important implications for “CO-dark” gas. We find a clear trend of the L_[C II]/L_TIRratio decreasing with increasing L_TIRin the full range. This suggests a strong link between the “[C II]-deficit” and the local physical conditions instead of global properties. 

   more » « less
4. The Stellar Content of NGC 3603 Revisited: Is the IMF Top Heavy? ^∗

   https://doi.org/10.3847/1538-4357/ae0e21  

   Massey, Philip; Morrell, Nidia I; Neugent, Kathryn F; Herzog, Monica; Drout, Maria R; O’Brien, Caitlin (November 2025, The Astrophysical Journal)

   Abstract Studies of the resolved stellar populations of young massive clusters have shown that the slope of the initial mass function (IMF) appears to be the same everywhere, with no dependence on stellar density or metallicity. At the same time, studies of integrated properties of galaxies usually conclude that the IMF does vary and must be top-heavy in starburst regions. In order to investigate this, we have carried out a long-term project to characterize the massive-star content of NGC 3603, the nearest giant Hiiregion, known to have a rich population of massive stars. We used both ground-based and Hubble Space Telescope (HST) imaging to obtain photometry, and we employed Gaia to establish membership. We obtained spectra of 128 stars using the Magellan 6.5 m telescope and HST, and we combine these data to produce a reddening map. After analyzing the data in the same way as we have for 25 other star-forming regions in the Milky Way and the Magellanic Clouds, we find that the IMF slope of NGC 3603 is quite normal compared to other clusters, with Γ = −0.9 ± 0.1. If anything, there are fewer very high mass (>65M_⊙) stars than one would expect by extrapolation from lower masses. This slope is also indistinguishable from what several studies have shown for R136 in the LMC, an even richer region. We speculate that the depreciation of the highest-mass bins in NGC 3603, but not in R136, may indicate that it is harder to form extremely massive stars at the higher metallicity of the Milky Way compared to that of the LMC. 

   more » « less
5. The MOSDEF survey: probing resolved stellar populations at z  ∼ 2 Using a new bayesian-defined morphology metric called patchiness

   https://doi.org/10.1093/mnras/stac3362  

   Fetherolf, Tara; Reddy, Naveen A; Shapley, Alice E; Kriek, Mariska; Siana, Brian; Coil, Alison L; Mobasher, Bahram; Freeman, William R; Price, Sedona H; Sanders, Ryan L; et al (December 2022, Monthly Notices of the Royal Astronomical Society)

   ABSTRACT We define a new morphology metric called ‘patchiness’ (P) that is sensitive to deviations from the average of a resolved distribution, does not require the galaxy centre to be defined, and can be used on the spatially resolved distribution of any galaxy property. While the patchiness metric has a broad range of applications, we demonstrate its utility by investigating the distribution of dust in the interstellar medium (ISM) of 310 star-forming galaxies at spectroscopic redshifts 1.36 < z < 2.66 observed by the MOSFIRE Deep Evolution Field survey. The stellar continuum reddening distribution, derived from high-resolution multiwaveband CANDELS/3D-HST imaging, is quantified using the patchiness, Gini, and M20 coefficients. We find that the reddening maps of high-mass galaxies, which are dustier and more metal-rich on average, tend to exhibit patchier distributions (high P) with the reddest components concentrated within a single region (low M20). Our results support a picture where dust is uniformly distributed in low-mass galaxies (≲1010 M⊙), implying efficient mixing of dust throughout the ISM. On the other hand, the dust distribution is patchier in high-mass galaxies (≳1010 M⊙). Dust is concentrated near regions of active star formation and dust mixing time-scales are expected to be longer in high-mass galaxies, such that the outskirt regions of these physically larger galaxies remain relatively unenriched. This study presents direct evidence for patchy dust distributions on scales of a few kpc in high-redshift galaxies, which previously has only been suggested as a possible explanation for the observed differences between nebular and stellar continuum reddening, star formation rate indicators, and dust attenuation curves. 

   more » « less