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Abstract
Aims. As a new approach to the study of resolved stellar populations in nearby galaxies, our goal is to demonstrate with a pilot study in NGC 300 that integral field spectroscopy with high spatial resolution and excellent seeing conditions reaches an unprecedented depth in severely crowded fields. Methods. Observations by MUSE with seven pointings in NGC 300 have resulted in data cubes that are analyzed in four ways: (1) Point spread function-fitting 3D spectroscopy with PampelMUSE, as already successfully pioneered in globular clusters, yields de-blended spectra of individually distinguishable stars, thus providing a complete inventory of blue and red supergiants, and asymptotic giant branch (AGB) stars of type M and C. The technique is also applicable to emission line point sources and provides samples of planetary nebulae (PNe) that are complete down to m5007 = 28. (2) Pseudo-monochromatic images, created at the wavelengths of the most important emission lines and corrected for continuum light with the P3D visualization tool, provide maps of H II regions, supernova remnants (SNR), and the diffuse interstellar medium (ISM) at a high level of sensitivity, where also faint point sources stand out and allow for the discovery of PNe, Wolf–Rayet (WR) stars, etc. (3) The use of the P3D line-fitting tool yields emission line fluxes, surface brightness, and kinematic information for gaseous objects, corrected for absorption line profiles of the underlying stellar population in the case of Hα. (4) Visual inspection of the data cubes by browsing through the row-stacked spectra image in P3D is demonstrated to be efficient for data mining and the discovery of background galaxies and unusual objects. Results. We present a catalog of luminous stars, rare stars such as WR, and other emission line stars, carbon stars, symbiotic star candidates, PNe, H II regions, SNR, giant shells, peculiar diffuse and filamentary emission line objects, and background galaxies, along with their spectra. Conclusions. The technique of crowded-field 3D spectroscopy, using the PampelMUSE code, is capable of deblending individual bright stars, the unresolved background of faint stars, gaseous nebulae, and the diffuse component of the ISM, resulting in unprecedented legacy value for observations of nearby galaxies with MUSE.
Highlights
The quest to understand the formation and evolution of galaxies has provided us with a wealth of data from imaging and spectroscopic surveys, most notably the Sloan Digital Sky Survey (SDSS), to quote just one prominent example (York et al 2000; Alam et al 2015)
In order to reduce the number of poor quality spectra that would not allow conversion of the fitting procedure, we set a threshold of S /N = 3 for the estimate computed by PampelMUSE and forwarded only spectra above the threshold to the ULySS code
The multi unit spectroscopic explorer instrument (MUSE) data obtained at the Very Large Telescope (VLT) show much finer detail and go significantly deeper than the WFI image, which can be appreciated well, for example, from the giant H ii region, denoted De100, that is cut between WFI and MUSE at the eastern edge of field (a), or the variety of giant shells and filaments in fields (a) . . . (j), which cannot be found at this level of detail in the WFI image
Summary
The quest to understand the formation and evolution of galaxies has provided us with a wealth of data from imaging and spectroscopic surveys, most notably the Sloan Digital Sky Survey (SDSS), to quote just one prominent example (York et al 2000; Alam et al 2015). During the extensive use of the P3D visualization tool, we incidentally noticed emission line signatures in the display of color-coded stacked spectra that did not seem to match any familiar pattern. As it turned out, we discovered several background galaxies in each of our fields that have redshifts of z = 0.13 . We discovered several background galaxies in each of our fields that have redshifts of z = 0.13 . 1.33, and even two candidates for Lyα emitting galaxies at redshifts z > 4
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