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1. MUSE crowded field 3D spectroscopy in NGC 300: IV. Planetary nebula luminosity function

   https://doi.org/10.1051/0004-6361/202244597  

   Soemitro, Azlizan A; Roth, Martin M; Weilbacher, Peter M; Ciardullo, Robin; Jacoby, George H; Monreal-Ibero, Ana; Castro, Norberto; Micheva, Genoveva (March 2023, Astronomy & Astrophysics)

   Aims.We perform a deep survey of planetary nebulae (PNe) in the spiral galaxy NGC 300 to construct its planetary nebula luminosity function (PNLF). We aim to derive the distance using the PNLF and to probe the characteristics of the most luminous PNe. Methods.We analysed 44 fields observed with MUSE at the VLT, covering a total area of ∼11 kpc². We find [O III]λ5007 sources using the differential emission line filter (DELF) technique. We identified PNe through spectral classification with the aid of the BPT diagram. The PNLF distance was derived using the maximum likelihood estimation technique. For the more luminous PNe, we also measured their extinction using the Balmer decrement. We estimated the luminosity and effective temperature of the central stars of the luminous PNe based on estimates of the excitation class and the assumption of optically thick nebulae. Results.We identify 107 PNe and derive a most-likely distance modulus $$ (m-M)_0 = 26.48^{+0.11}_{-0.26} $$ ($$ d = 1.98^{+0.10}_{-0.23} $$ Mpc). We find that the PNe at the PNLF cutoff exhibit relatively low extinction, with some high-extinction cases caused by local dust lanes. We present the lower limit luminosities and effective temperatures of the central stars for some of the brighter PNe. We also identify a few Type I PNe that come from a young population with progenitor masses > 2.5 M_⊙but do not populate the PNLF cutoff. Conclusions.The spatial resolution and spectral information of MUSE allow precise PN classification and photometry. These capabilities also enable us to resolve possible contamination by diffuse gas and dust, improving the accuracy of the PNLF distance to NGC 300. 

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2. The Effect of Superpositions on the Planetary Nebula Luminosity Function

   https://doi.org/10.3847/1538-4357/acc9bd  

   Chase, Owen; Ciardullo, Robin; Roth, Martin M.; Jacoby, George H. (June 2023, The Astrophysical Journal)

   Abstract Planetary nebula (PN) surveys in systems beyond ∼10 Mpc often find high-excitation, point-like sources with [O iii ] λ 5007 fluxes greater than the apparent bright-end cutoff of the planetary nebula luminosity function (PNLF). Here we identify PN superpositions as one likely cause for the phenomenon and describe the proper procedures for deriving PNLF distances when object blends are a possibility. We apply our technique to two objects: a model Virgo-distance elliptical galaxy observed through a narrowband interference filter, and the Fornax lenticular galaxy NGC 1380 surveyed with the MUSE integral-field unit spectrograph. Our analyses show that even when the most likely distance to a galaxy is unaffected by the possible presence of PN superpositions, the resultant value will still be biased toward too small a distance due to the asymmetrical nature of the error bars. We discuss the future of the PNLF in an era where current ground-based instrumentation can push the technique to distances beyond ∼35 Mpc. 

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3. The Hubble Tension in Our Own Backyard: DESI and the Nearness of the Coma Cluster

   https://doi.org/10.3847/2041-8213/ada0bd  

   Scolnic, Daniel; Riess, Adam G; Murakami, Yukei S; Peterson, Erik R; Brout, Dillon; Acevedo, Maria; Carreres, Bastien; Jones, David O; Said, Khaled; Howlett, Cullan; et al (January 2025, The Astrophysical Journal Letters)

   Abstract The Dark Energy Spectroscopic Instrument (DESI) collaboration measured a tight relation between the Hubble constant (H₀) and the distance to the Coma cluster using the fundamental plane (FP) relation of the deepest, most homogeneous sample of early-type galaxies. To determineH₀, we measure the distance to Coma by several independent routes, each with its own geometric reference. We measure the most precise distance to Coma from 13 Type Ia supernovae (SNe Ia) in the cluster with a mean standardized brightness of $m_B^0=15.710\pm 0.040$mag. Calibrating the absolute magnitude of SNe Ia with the Hubble Space Telescope (HST) distance ladder yieldsD_Coma = 98.5 ± 2.2 Mpc, consistent with its canonical value of 95–100 Mpc. This distance results inH₀ = 76.5 ± 2.2 km s⁻¹Mpc⁻¹from the DESI FP relation. Inverting the DESI relation by calibrating it instead to the Planck+ΛCDM value ofH₀ = 67.4 km s⁻¹Mpc⁻¹implies a much greater distance to Coma,D_Coma = 111.8 ± 1.8 Mpc, 4.6σbeyond a joint, direct measure. Independent of SNe Ia, the HST Key Project FP relation as calibrated by Cepheids, the tip of the red giant branch from JWST, or HST near-infrared surface brightness fluctuations all yieldD_Coma < 100 Mpc, in joint tension themselves with the Planck-calibrated route at >3σ. From a broad array of distance estimates compiled back to 1990, it is hard to see how Coma could be located as far as the Planck+ΛCDM expectation of >110 Mpc. By extending the Hubble diagram to Coma, a well-studied location in our own backyard whose distance was in good accord well before the Hubble tension, DESI indicates a more pervasive conflict between our knowledge of local distances and cosmological expectations. We expect future programs to refine the distance to Coma and nearer clusters to help illuminate this new local window on the Hubble tension. 

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4. The Planetary Nebula Luminosity Function in the Era of Precision Cosmology

   https://doi.org/10.3389/fspas.2022.896326  

   Ciardullo, Robin (May 2022, Frontiers in Astronomy and Space Sciences)

   One of the great surprises of the late 1980s was the discovery that the [O III] λ 5007 planetary nebula luminosity function (PNLF) could be used as a precision extragalactic standard candle. Despite the lack of any robust theory for the phenomenon, the technique passed a myriad of internal and external tests, and became an extremely reliable tool for obtaining distances to large galaxies within ∼ 20 Mpc. But in more recent years, the use of the technique has declined, due in part to the changing landscape of cosmology. Here we review the history of the PNLF, the experiments that confirmed its utility, and the reasons why interest in the method faded at the turn of the millennium. We also describe how and why the PNLF is making a comeback, and present some of the method’s recent results. Finally, we discuss how the PNLF must be analyzed in the era of precision cosmology, and detail the issues that must be overcome in order to address the current tension between local measures of the Hubble constant and values derived from the microwave background. If these issues can be understood, then the PNLF can provide a useful cross-check on distance measurements out to ∼ 40  Mpc. 

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5. The TRGB−SBF Project. III. Refining the HST Surface Brightness Fluctuation Distance Scale Calibration with JWST

   https://doi.org/10.3847/1538-4357/addfd6  

   Jensen, Joseph B; Blakeslee, John P; Cantiello, Michele; Cowles, Mikaela; Anand, Gagandeep S; Tully, R Brent; Kourkchi, Ehsan; Raimondo, Gabriella (July 2025, The Astrophysical Journal)

   Abstract The TRGB−SBF Project team is developing an independent distance ladder using a geometrical calibration of the tip of the red giant branch (TRGB) method in elliptical galaxies that can, in turn, be used to set the surface brightness fluctuation (SBF) distance scale independent of Cepheid variables and Type Ia supernovae. The purpose of this project is to measure the local expansion rate of the Universe independently of the methods that are most at odds with the theoretically predicted value of the Hubble–Lemaître constantH₀, and therefore isolate the influence of potential systematic observational errors. In this paper, we use JWST TRGB distances calibrated using the megamaser galaxy NGC 4258 to determine a new Cepheid-independent SBF zero-point with the Hubble Space Telescope. This new calibration, along with improved optical color measurements from Pan-STARRS and DECam, gives an updated value ofH₀= 73.8 ± 0.7 (statistical) ±2.3 (systematic) km s⁻¹Mpc⁻¹that is virtually identical to the SBF Hubble–Lemaître constant measured by J. P. Blakeslee et al. 

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