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1. SN 2018is: A low-luminosity Type IIP supernova with narrow hydrogen emission lines at early phases

   https://doi.org/10.1051/0004-6361/202452507  

   Dastidar, R; Misra, K; Valenti, S; Sand, D J; Pastorello, A; Reguitti, A; Pignata, G; Benetti, S; Bose, S; Gangopadhyay, A; et al (February 2025, Astronomy & Astrophysics)

   We present a comprehensive photometric and spectroscopic study of the Type IIP supernova (SN) 2018is. TheVband luminosity and the expansion velocity at 50 days post-explosion are −15.1 ± 0.2 mag (corrected for A_V= 1.34 mag) and 1400 km s⁻¹, classifying it as a low-luminosity SN II. The recombination phase in theVband is shorter, lasting around 110 days, and exhibits a steeper decline (1.0 mag per 100 days) compared to most other low-luminosity SNe II. Additionally, the optical and near-infrared spectra display hydrogen emission lines that are strikingly narrow, even for this class. The Fe IIand Sc IIline velocities are at the lower end of the typical range for low-luminosity SNe II. Semi-analytical modelling of the bolometric light curve suggests an ejecta mass of ∼8 M_⊙, corresponding to a pre-supernova mass of ∼9.5 M_⊙, and an explosion energy of ∼0.40 × 10⁵¹erg. Hydrodynamical modelling further indicates that the progenitor had a zero-age main sequence mass of 9 M_⊙, coupled with a low explosion energy of 0.19 × 10⁵¹erg. The nebular spectrum reveals weak [O I]λλ6300,6364 lines, consistent with a moderate-mass progenitor, while features typical of Fe core-collapse events, such as He I, [C I], and Fe I, are indiscernible. However, the redder colours and low ratio of Ni to Fe abundance do not support an electron-capture scenario either. As a low-luminosity SN II with an atypically steep decline during the photospheric phase and remarkably narrow emission lines, SN 2018is contributes to the diversity observed within this population. 

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2. Searching for C ii Emission from the First Sample of z ∼ 6 O i Absorption-associated Galaxies with the Atacama Large Millimeter/submillimeter Array

   https://doi.org/10.3847/1538-4357/ad00b8  

   Wu, Yunjing; Cai, Zheng; Li, Jianan; Finlator, Kristian; Neeleman, Marcel; Prochaska, J Xavier; Emonts, Bjorn_H C; Zhang, Shiwu; Wang, Feige; Yang, Jinyi; et al (November 2023, The Astrophysical Journal)

   Abstract We report the first statistical analyses of [Cii] and dust continuum observations in six strong Oiabsorber fields at the end of the reionization epoch obtained by the Atacama Large Millimeter/submillimeter Array (ALMA). Combined with one [Cii] emitter reported in Wu et al., we detect one Oi-associated [Cii] emitter in six fields. At redshifts of Oiabsorbers in nondetection fields, no emitters are brighter than our detection limit within impact parameters of 50 kpc and velocity offsets between ±200 km s⁻¹. The averaged [Cii]-detection upper limit is <0.06 Jy km s⁻¹(3σ), corresponding to the [Cii] luminosity ofL_[CII]< 5.8 × 10⁷L_⊙and the [Cii]-based star formation rate of SFR_[CII]<5.5M_⊙yr⁻¹. Cosmological simulations suggest that only ∼10^−2.5[Cii] emitters around Oiabsorbers have comparable SFR to our detection limit. Although the detection in one out of six fields is reported, an order of magnitude number excess of emitters obtained from our ALMA observations supports that the contribution of massive galaxies that caused the metal enrichment cannot be ignored. Further, we also found 14 tentative galaxy candidates with a signal-to-noise ratio of ≈4.3 at large impact parameters (>50 kpc) and having larger outflow velocities within ±600 km s⁻¹. If these detections are confirmed in the future, then the mechanism of pushing metals at larger distances with higher velocities needs to be further explored from the theoretical side. 

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3. SDSS-IV MaNGA: Understanding Ionized Gas Turbulence Using Integral Field Spectroscopy of 4500 Star-forming Disk Galaxies

   https://doi.org/10.3847/1538-4357/ac5620  

   Law, David R.; Belfiore, Francesco; Bershady, Matthew A.; Cappellari, Michele; Drory, Niv; Masters, Karen L.; Westfall, Kyle B.; Bizyaev, Dmitry; Bundy, Kevin; Pan, Kaike; et al (March 2022, The Astrophysical Journal)

   Abstract The Sloan Digital Sky Survey MaNGA program has now obtained integral field spectroscopy for over 10,000 galaxies in the nearby universe. We use the final MaNGA data release DR17 to study the correlation between ionized gas velocity dispersion and galactic star formation rate, finding a tight correlation in whichσ_Hαfrom galactic Hiiregions increases significantly from ∼18–30 km s⁻¹, broadly in keeping with previous studies. In contrast,σ_Hαfrom diffuse ionized gas increases more rapidly from 20–60 km s⁻¹. Using the statistical power of MaNGA, we investigate these correlations in greater detail using multiple emission lines and determine that the observed correlation ofσ_Hαwith local star formation rate surface density is driven primarily by the global relation of increasing velocity dispersion at higher total star formation rate, as are apparent correlations with stellar mass. Assuming Hiiregion models consistent with our finding thatσ_[OIII]<σ_Hα<σ_{[O I]}, we estimate the velocity dispersion of the molecular gas in which the individual Hiiregions are embedded, finding valuesσ_Mol= 5–30 km s⁻¹consistent with ALMA observations in a similar mass range. Finally, we use variations in the relation with inclination and disk azimuthal angle to constrain the velocity dispersion ellipsoid of the ionized gasσ_z/σ_r= 0.84 ± 0.03 andσ_ϕ/σ_r= 0.91 ± 0.03, similar to that of young stars in the Galactic disk. Our results are most consistent with the theoretical models in which turbulence in modern galactic disks is driven primarily by star formation feedback. 

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4. The Outflowing [O ii] Nebulae of Compact Starburst Galaxies at z ∼ 0.5

   https://doi.org/10.3847/1538-4357/ad7b0c  

   Perrotta, Serena; Coil, Alison L; Rupke, David_S N; Ning, Wenmeng; Duong, Brendan; Diamond-Stanic, Aleksandar M; Fielding, Drummond B; Geach, James E; Hickox, Ryan C; Moustakas, John; et al (November 2024, The Astrophysical Journal)

   Abstract High-velocity outflows are ubiquitous in compact, massive (M_*∼ 10¹¹M_⊙),z∼ 0.5 galaxies with extreme star formation surface densities (Σ_SFR∼ 2000M_⊙yr⁻¹kpc⁻²). We have previously detected and characterized these outflows using Mgiiabsorption lines. To probe their full extent, we present Keck/KCWI integral field spectroscopy of the [Oii] and Mgiiemission nebulae surrounding all of the 12 galaxies in this study. We find that [Oii] is more effective than Mgiiin tracing low surface brightness, extended emission in these galaxies. The [Oii] nebulae are spatially extended beyond the stars, with radial extentR₉₀between 10 and 40 kpc. The nebulae exhibit nongravitational motions, indicating galactic outflows with maximum blueshifted velocities ranging from −335 to −1920 km s⁻¹. The outflow kinematics correlate with the bursty star formation histories of these galaxies. Galaxies with the most recent bursts of star formation (within the last <3 Myr) exhibit the highest central velocity dispersions (σ≳ 400 km s⁻¹), while the oldest bursts have the lowest-velocity outflows. Many galaxies exhibit both high-velocity cores and more extended, slower-moving gas indicative of multiple outflow episodes. The slower, larger outflows occurred earlier and have decelerated as they propagate into the circumgalactic medium and mix on timescales ≳50 Myr. 

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5. Braving the Storm: Quantifying Disk-wide Ionized Outflows in the Large Magellanic Cloud with ULLYSES

   https://doi.org/10.3847/1538-4357/ad64d2  

   Zheng_郑, Yong 永; Tchernyshyov, Kirill; Olsen, Knut; Choi, Yumi; Bustard, Chad; Roman-Duval, Julia; Zhu, Robert; Di_Teodoro, Enrico M; Werk, Jessica; Putman, Mary; et al (October 2024, The Astrophysical Journal)

   Abstract The Large Magellanic Cloud (LMC) is home to many Hiiregions, which may lead to significant outflows. We examine the LMC’s multiphase gas (T∼10^4-5K) in Hi, Sii, Siiv, and Civusing 110 stellar sight lines from the Hubble Space Telescope’s Ultraviolet Legacy Library of Young Stars as Essential Standards program. We develop a continuum fitting algorithm based on the concept of Gaussian process regression and identify reliable LMC interstellar absorption overv_helio= 175–375 km s⁻¹. Our analyses show disk-wide ionized outflows in Siivand Civacross the LMC with bulk velocities of ∣v_{out, bulk}∣ ∼ 20–60 km s⁻¹, which indicates that most of the outflowing mass is gravitationally bound. The outflows’ column densities correlate with the LMC’s star formation rate surface densities (Σ_SFR), and the outflows with higher Σ_SFRtend to be more ionized. Considering outflows from both sides of the LMC as traced by Civ, we conservatively estimate a total outflow rate of ${\dot{M}}_{\mathrm{out}}\gtrsim 0.03M_{\odot }{\mathrm{yr}}^{-1}$and a mass-loading factor ofη≳ 0.15. We compare the LMC’s outflows with those detected in starburst galaxies and simulation predictions, and find a universal scaling relation of $\mid v_{\mathrm{out},\mathrm{bulk}}\mid \propto {\mathrm{\Sigma }}_{\mathrm{SFR}}^{0.23}$over a wide range of star-forming conditions (Σ_SFR∼ 10^−4.5–10²M_⊙yr⁻¹kpc⁻²). Lastly, we find that the outflows are corotating with the LMC’s young stellar disk and the velocity field does not seem to be significantly impacted by external forces; we thus speculate on the existence of a bow shock leading the LMC, which may have shielded the outflows from ram pressure as the LMC orbits the Milky Way. 

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