George H. Jacoby

Aims. Distance measurements using the planetary nebula luminosity function (PNLF) rely on the bright-end cutoff magnitude ( M ^* ), which is defined by a number of the [O III ] λ 5007-brightest planetary nebulae (PNe). In early-type galaxies (ETGs), the formation of these PNe is enigmatic; the population is typically too old to form the expected M ^* PNe from single star evolution. We aim to provide a viable solution to this problem. Methods. We selected five ETGs with known MUSE-PNLF distances. The MUSE instrument allows us to calculate the PNLF and consistently investigate the underlying stellar populations. Using stellar population synthesis, we derived the population age, star formation history, metallicity, and alpha abundance. We compared these parameters to the PNLF variables: the absolute magnitude of the bright cutoff ( M ^* ) and luminosity-specific PN number at the top 0.5 mag of the PNLF ( α _0.5 ). We also compare our results with PNe In Cosmological Simulations (PICS) model applied to Magneticum Pathfinder analogue galaxies. Results. The average mass-weighted ages and metallicities of the stellar populations in our datasets are typically old (9 < Age < 13.5 Gyr) and rather metal rich (−0.4 < [M/H] < +0.2). We find the value of M ^* to be independent of age and metallicity in these ages and metallicity intervals. We observed a positive correlation between α _0.5 values and the mass fraction of stellar population ages of 2–10 Gyr, implying that most of the PNe originate from stars with intermediate ages. Similar trends are also found in the PICS analogue galaxies. Conclusions. We show that when ∼2% of the stellar mass present is younger than 10 Gyr, it is sufficient to form the M ^* PNe in ETGs. We also present observing requirements for an ideal PNLF distance determination in ETGs.

We examine the relationship between circumnebular extinction and core mass for sets of [O iii]-bright planetary nebulae (PNe) in the Large Magellanic Cloud and M31. We confirm that for PNe within 1 magnitude of the planetary nebula luminosity function’s (PNLF’s) bright-end cutoff magnitude (M ^*), higher core-mass PNe are disproportionally affected by greater circumnebular extinction. We show that this result can explain why the PNLF cutoff is so insensitive to population age. In younger populations, the higher-mass, higher-luminosity cores experience greater circumnebular extinction from the dust created by their asymptotic giant branch (AGB) progenitors compared to the lower-mass cores. We further show that when our core-mass–nebular extinction law is combined with post-AGB stellar evolutionary models, the result is a large range of population ages where the brightest PNe all have nearly identical [O iii] luminosities. Finally, we note that while there is some uncertainty about whether the oldest stellar populations can produce PNe as bright as M ^*, this issue is resolved if the initial–final mass relation (IFMR) for the lowest-mass stars results in slightly more massive cores, as observed in some clusters. Alternatively, introducing a small amount of intrinsic scatter (0.022 M _⊙) into the IFMR also addresses this uncertainty.

We examine the relationship between circumnebular extinction and core mass for sets of [O III]-bright planetary nebulae (PNe) in the Large Magellanic Cloud and M31. We confirm that for PNe within one magnitude of the Planetary Nebula Luminosity Function's (PNLF's) bright-end cutoff magnitude (M*), higher core-mass PNe are disproportionally affected by greater circumnebular extinction. We show that this result can explain why the PNLF cutoff is so insensitive to population age. In younger populations, the higher-mass, higher-luminosity cores experience greater circumnebular extinction from the dust created by their AGB progenitors compared to the lower-mass cores. We further show that when our core-mass-nebular extinction law is combined with post-AGB stellar evolutionary models, the result is a large range of population ages where the brightest PNe all have nearly identical [O III] luminosities. Finally, we note that while there is some uncertainty about whether the oldest stellar populations can produce planetary nebulae as bright as M*, this issue is resolved if the initial-final mass relation (IFMR) for the lowest-mass stars results in slightly more massive cores, as observed in some clusters. Alternatively, introducing a small amount of intrinsic scatter (0.022 Msun) into the IFMR also addresses this uncertainty.

Thanks to the MUSE integral field spectrograph on the VLT, extragalactic distance measurements with the [O III] 5007 A planetary nebula luminosity function (PNLF) are now possible out to approx. 40 Mpc. Here we analyze the VLT/MUSE data for 20 galaxies from the ESO public archive to identify the systems' planetary nebulae (PNe) and determine their PNLF distances. Three of the galaxies do not contain enough PNe for a robust measure of the PNLF, and the results for one other system are compromised by the galaxy's internal extinction. However, we obtain robust PNLF distances for the remaining 16 galaxies, two of which are isolated and beyond 30 Mpc in a relatively unperturbed Hubble flow. From these data, we derive a Hubble Constant of 74.2 +/- 7.2 (stat) +/-3.7 (sys) km/s/Mpc, a value that is very similar to that found from other quality indicators (e.g., Cepheids, the tip of the red giant branch, and surface brightness fluctuations). At present, the uncertainty is dominated by the small number of suitable galaxies in the ESO archival and their less than ideal observing conditions and calibrations. Based on our experience with these systems, we identify the observational requirements necessary for the PNLF to yield a competitive value for H0 that is independent of the SN Ia distance scale, and help resolve the current tension in the Hubble constant.

Thanks to the MUSE integral field spectrograph on board the Very Large Telescope (VLT), extragalactic distance measurements with the [O iii] λ5007 planetary nebula luminosity function (PNLF) are now possible out to ∼40 Mpc. Here we analyze the VLT/MUSE data for 20 galaxies from the ESO public archive to identify the systems’ planetary nebulae (PNe) and determine their PNLF distances. Three of the galaxies do not contain enough PNe for a robust measure of the PNLF, and the results for one other system are compromised of the galaxy’s internal extinction. However, we obtain robust PNLF distances for the remaining 16 galaxies, two of which are isolated and beyond 30 Mpc in a relatively unperturbed Hubble flow. From these data, we derive a Hubble constant of 74.2 ± 7.2 (stat) ±3.7 (sys) km s⁻¹ Mpc⁻¹, a value that is very similar to that found from other quality indicators (e.g., Cepheids, the tip of the red giant branch, and surface brightness fluctuations). At present, the uncertainty is dominated by the small number of suitable galaxies in the ESO archive and their less-than-ideal observing conditions and calibrations. Based on our experience with these systems, we identify the observational requirements necessary for the PNLF to yield a competitive value for H ₀ that is independent of the Type Ia supernova distance scale.

A quarter of a century has passed since the observing technique of integral field spectroscopy (IFS) was first applied to planetary nebulae (PNe). Progress after the early experiments was relatively slow, mainly because of the limited field-of-view (FoV) of first generation instruments. With the advent of MUSE at the ESO Very Large Telescope, this situation has changed. MUSE is a wide field-of-view, high angular resolution, one-octave spanning optical integral field spectrograph with high throughput. Its major science mission has enabled an unprecedented sensitive search for Lyα emitting galaxies at redshift up to z=6.5. This unique property can be utilized for faint objects at low redshift as well. It has been demonstrated that MUSE is an ideal instrument to detect and measure extragalactic PNe with high photometric accuracy down to very faint magnitudes out to distances of 30 Mpc, even within high surface brightness regions of their host galaxies. When coupled with a differential emission line filtering (DELF) technique, MUSE becomes far superior to conventional narrow-band imaging, and therefore MUSE is ideal for accurate Planetary Nebula Luminosity Function (PNLF) distance determinations. MUSE enables the PNLF to become a competitive tool for an independent measure of the Hubble constant, and stellar population studies of the host galaxies that present a sufficiently large number of PNe.

The Multi-Unit Spectroscopic Explorer (MUSE) has enabled a renaissance of the planetary nebula luminosity function (PNLF) as a standard candle. In the case of NGC 300, we learned that the precise spectrophotometry of MUSE was crucial to obtain an accurate PNLF distance. We present the advantage of the integral field spectrograph compared to the slit spectrograph in delivering precise spectrophotometry by simulating a slit observation on integral field spectroscopy data. We also discuss the possible systematic shift in measuring the PNLF distance using the least-square method, especially when the PNLF cutoff is affected by small number statistics.

We analyzed VLT/MUSE data for 20 galaxies in the ESO public archive to identify their systems’ planetary nebulae (PNe). Using the differential emission line filter (DELF) technique, we performed photometry of the galaxies’ PNe and determined their distances via the planetary nebula luminosity function (PNLF). Of the 16 galaxies for which a quality PNLF could be formed, two are isolated and more distant than 30 Mpc and therefore, relatively unaffected by Hubble Flow peculiar velocities. Using these data, we derived a Hubble Constant of 74.2 ± 7.2 (stat) ±3.7 (sys) km s⁻¹ Mpc⁻¹, a value that is similar to that found from other quality indicators (e.g., Cepheids, the tip of the red giant branch, and surface brightness fluctuations), but with a larger uncertainty due to the small number of galaxies. We describe how to improve PNLF measurements so that the precision of the technique is comparable to that of other quality distance indicators. We also describe a path forward in the era of ELTs that supersedes current techniques.

Planetary nebula (PN) surveys in systems beyond ∼10 Mpc often find high-excitation, point-like sources with [O iii] λ5007 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.