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1. The Hubble Constant from Infrared Surface Brightness Fluctuation Distances*

   https://doi.org/10.3847/1538-4357/abe86a  

   Blakeslee, John P. ; Jensen, Joseph B. ; Ma, Chung-Pei ; Milne, Peter A. ; Greene, Jenny E. ( April 2021 , The Astrophysical Journal)

   We present a measurement of the Hubble constantH₀from surface brightness fluctuation (SBF) distances for 63 bright, mainly early-type galaxies out to 100 Mpc observed with the WFC3/IR on the Hubble Space Telescope (HST). The sample is drawn from several independent HST imaging programs using the F110W bandpass, with the majority of the galaxies being selected from the MASSIVE survey. The distances reach the Hubble flow with a median statistical uncertainty per measurement of 4%. We construct the Hubble diagram with these IR SBF distances and constrainH₀using four different treatments of the galaxy velocities. For the SBF zero-point calibration, we use both the existing tie to Cepheid variables, updated for consistency with the latest determination of the distance to the Large Magellanic Cloud from detached eclipsing binaries, and a new tie to the tip of the red giant branch (TRGB) calibrated from the maser distance to NGC 4258. These two SBF calibrations are consistent with each other and with theoretical predictions from stellar population models. From a weighted average of the Cepheid and TRGB calibrations, we deriveH₀= 73.3 ± 0.7 ± 2.4 km s⁻¹Mpc⁻¹, where the error bars reflect the statistical and systematic uncertainties. This result accords well with recent measurements ofH₀from Type Ia supernovae, time delays in multiply lensed quasars, and water masers. The systematic uncertainty could be reduced to below 2% by calibrating the SBF method with precision TRGB distances for a statistical sample of massive early-type galaxies out to the Virgo cluster measured with the James Webb Space Telescope.

    

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2. A new measurement of the Hubble constant using Type Ia supernovae calibrated with surface brightness fluctuations

   https://doi.org/10.1051/0004-6361/202039196  

   Khetan, Nandita ; Izzo, Luca ; Branchesi, Marica ; Wojtak, Radosław ; Cantiello, Michele ; Murugeshan, Chandrashekar ; Agnello, Adriano ; Cappellaro, Enrico ; Della Valle, Massimo ; Gall, Christa ; et al ( March 2021 , Astronomy & Astrophysics)

   null (Ed.)

   We present a new calibration of the peak absolute magnitude of Type Ia supernovae (SNe Ia) based on the surface brightness fluctuations (SBF) method, aimed at measuring the value of the Hubble constant. We build a sample of calibrating anchors consisting of 24 SNe hosted in galaxies that have SBF distance measurements. Applying a hierarchical Bayesian approach, we calibrate the SN Ia peak luminosity and extend the Hubble diagram into the Hubble flow by using a sample of 96 SNe Ia in the redshift range 0.02 <  z  < 0.075, which was extracted from the Combined Pantheon Sample. We estimate a value of H 0  = 70.50 ± 2.37 (stat.) ± 3.38 (sys.) km s −1 Mpc −1 (i.e., 3.4% stat., 4.8% sys.), which is in agreement with the value obtained using the tip of the red giant branch calibration. It is also consistent, within errors, with the value obtained from SNe Ia calibrated with Cepheids or the value inferred from the analysis of the cosmic microwave background. We find that the SNe Ia distance moduli calibrated with SBF are on average larger by 0.07 mag than those calibrated with Cepheids. Our results point to possible differences among SNe in different types of galaxies, which could originate from different local environments and/or progenitor properties of SNe Ia. Sampling different host galaxy types, SBF offers a complementary approach to using Cepheids, which is important in addressing possible systematics. As the SBF method has the ability to reach larger distances than Cepheids, the impending entry of the Vera C. Rubin Observatory and JWST into operation will increase the number of SNe Ia hosted in galaxies where SBF distances can be measured, making SBF measurements attractive for improving the calibration of SNe Ia, as well as in the estimation of H 0 . 

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3. A Uniform Type Ia Supernova Distance Ladder with the Zwicky Transient Facility: Absolute Calibration Based on the Tip of the Red Giant Branch Method

   https://doi.org/10.3847/1538-4357/ac7ceb  

   Dhawan, Suhail ; Goobar, Ariel ; Johansson, Joel ; Jang, In Sung ; Rigault, Mickael ; Harvey, Luke ; Maguire, Kate ; Freedman, Wendy L. ; Madore, Barry F. ; Smith, Mathew ; et al ( August 2022 , The Astrophysical Journal)

   Abstract The current Cepheid-calibrated distance ladder measurement of H 0 is reported to be in tension with the values inferred from the cosmic microwave background (CMB), assuming standard cosmology. However, some tip of the red giant branch (TRGB) estimates report H 0 in better agreement with the CMB. Hence, it is critical to reduce systematic uncertainties in local measurements to understand the Hubble tension. In this paper, we propose a uniform distance ladder between the second and third rungs, combining Type Ia supernovae (SNe Ia) observed by the Zwicky Transient Facility (ZTF) with a TRGB calibration of their absolute luminosity. A large, volume-limited sample of both calibrator and Hubble flow SNe Ia from the same survey minimizes two of the largest sources of systematics: host-galaxy bias and nonuniform photometric calibration. We present results from a pilot study using the existing TRGB distance to the host galaxy of ZTF SN Ia SN 2021rhu (aka ZTF21abiuvdk) in NGC7814. Combining the ZTF calibrator with a volume-limited sample from the first data release of ZTF Hubble flow SNe Ia, we infer H 0 = 76.94 ± 6.4 km s −1 Mpc −1 , an 8.3% measurement. The error budget is dominated by the single object calibrating the SN Ia luminosity in this pilot study. However, the ZTF sample includes already five other SNe Ia within ∼20 Mpc for which TRGB distances can be obtained with the Hubble Space Telescope. Finally, we present the prospects of building this distance ladder out to 80 Mpc with James Webb Space Telescope observations of more than 100 ZTF SNe Ia. 

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4. Hubble Space Telescope Imaging of Isolated Local Volume Dwarfs GALFA Dw3 and Dw4

   https://doi.org/10.3847/1538-4357/ac356c  

   Bennet, P. ; Sand, D. J. ; Crnojević, D. ; Weisz, D. R. ; Caldwell, N. ; Guhathakurta, P. ; Hargis, J. R. ; Karunakaran, A. ; Mutlu-Pakdil, B. ; Olszewski, E. ; et al ( January 2022 , The Astrophysical Journal)

   We present observations of the dwarf galaxies GALFA Dw3 and GALFA Dw4 with the Advanced Camera for Surveys on the Hubble Space Telescope. These galaxies were initially discovered as optical counterparts to compact Hiclouds in the GALFA survey. Both objects resolve into stellar populations which display old red giant branch (RGB), younger helium-burning, and massive main sequence stars. We use the tip of the RGB method to determine the distance to each galaxy, finding distances of${7.61}_{-0.29}^{+0.28}$Mpc and${3.10}_{-0.17}^{+0.16}$Mpc, respectively. With these distances we show that both galaxies are extremely isolated, with no other confirmed objects within ∼1.5 Mpc of either dwarf. GALFA Dw4 is also found to be unusually compact for a galaxy of its luminosity. GALFA Dw3 and Dw4 contain Hiiregions with young star clusters and an overall irregular morphology; they show evidence of ongoing star formation through both ultraviolet and Hαobservations and are therefore classified as dwarf irregulars (dIrrs). The star formation histories of these two dwarfs show distinct differences: Dw3 shows signs of a recently ceased episode of active star formation across the entire dwarf, while Dw4 shows some evidence for current star formation in spatially limited Hiiregions. Compact Hisources offer a promising method for identifying isolated field dwarfs in the Local Volume, including GALFA Dw3 and Dw4, with the potential to shed light on the driving mechanisms of dwarf galaxy formation and evolution.

    

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5. Stellar masses of clumps in gas-rich, turbulent disc galaxies

   https://doi.org/10.1093/mnras/stac622  

   Ambachew, Liyualem ; Fisher, Deanne B ; Glazebrook, Karl ; Girard, Marianne ; Obreschkow, Danail ; Abraham, Roberto ; Bolatto, Alberto ; Lenkić, Laura ; Damjanov, Ivana ( March 2022 , Monthly Notices of the Royal Astronomical Society)

   ABSTRACT In this paper, we use Hubble Space Telescope/WFC3 observations of six galaxies from the DYnamics of Newly Assembled Massive Object (DYNAMO) survey, combined with stellar population modelling of the SED, to determine the stellar masses of DYNAMO clumps. The DYNAMO sample has been shown to have properties similar to z ≈ 1.5 turbulent, clumpy discs. DYNAMO sample clump masses offer a useful comparison for studies of z > 1 in that the galaxies have the same properties, yet the observational biases are significantly different. Using DYNAMO, we can more easily probe rest-frame near-IR wavelengths and also probe finer spatial scales. We find that the stellar mass of DYNAMO clumps is typically 107−108M⊙. We employ a technique that makes non-parametric corrections in removal of light from nearby clumps, and carries out a locally determined disc subtraction. The process of disc subtraction is the dominant effect, and can alter clump masses at the 0.3 dex level. Using these masses, we investigate the stellar mass function (MF) of clumps in DYNAMO galaxies. DYNAMO stellar MFs follow a declining power law with slope α ≈ −1.4, which is slightly shallower than, but similar to what is observed in z > 1 lensed galaxies. We compare DYNAMO clump masses to results of simulations. The masses and galactocentric position of clumps in DYNAMO galaxies are more similar to long-lived clumps in simulations. Similar to recent DYNAMO results on the stellar population gradients, these results are consistent with simulations that do not employ strong ‘early’ radiative feedback prescriptions. 

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