Integral Field Spectroscopy: a disruptive innovation for observations of Planetary Nebulae and the PNLF

TL;DR

The paper reviews how integral field spectroscopy, led by MUSE, has transformed the spectrophotometry of planetary nebulae and the use of the PNLF as a distance indicator. It explains the limitations of early IFS due to small fields of view and introduces DELF as a technique that leverages MUSE’s data-cube capabilities to achieve precise, continuum-subtracted emission-line photometry. Benchmark tests demonstrate improved sensitivity and reliability for PN-based distance measurements, with implications for an independent determination of the Hubble constant. The work outlines a path forward for expanding PNLF applications to larger distances and crowded environments, and notes future prospects with upcoming facilities to push reach toward ~100 Mpc.

Abstract

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.

Figures (8)

• Figure 1: A reminiscence of IAU Symposium 131 from 1987 in Mexico City, organized by Silvia Torres-Peimbert and Manuel Peimbert, that publicly marked the birth of the PNLF as a standard candle.
• Figure 2: The pioneering fiber bundle integral field unit DensePak II for the KPNO 4m Telescope. The unit featured 49 fibers and subtended $16 \times19$ arcsec$^2$ on the sky (from 1988ASPC....3..113B.
• Figure 3: Left: PMAS instrument at the Cassegrain focus of the Calar Alto 3.5m Telescope (1). Right: square lens array IFU (2) with a standard FoV of $8\times8$ arcsec$^2$; fiber bundle IFU PPaK with hexagonal footprint and FoV of $74\times65$ arcsec$^2$, surrounded by 6 bundles to sample the sky background (3).
• Figure 4: PNe in M31 observed with IFS. Adapted from 2004ApJ...603..531R. Top: the bold outlined frames show reconstructed maps obtained from PMAS data cubes in [O III] $\lambda5007$Å for PN27, PN29, PN56, PN181, and PN276 from the sample of 1989ApJ...339...53C; Fabry Perot CCD images are shown on the left for comparison (see explanation in the text). Bottom: corresponding spectra obtained with PMAS, MPFS at the Selentchuk 6m telescope, and with INTEGRAL at the WHT. PN276 is clearly identifiable as a supernova remnant.
• Figure 5: MUSE at the ESO VLT. The complex arrangement of 24 spectrographs on the Nasmyth platform of UT4 is shown in (1), credit: Ghaouti Hansali (CRAL). The 24 spectrographs are fed by image slicers whose purpose is to map the input sky field into a staggered set of mini-slits. Each image slicer consists of an arrangement of an image dissector array (2) with a focusing mirror array (3), that sends an ordered set of sliced sky area to its associated spectrograph module. Credit: Florence Laurent, CRAL.