The survey of Planetary Nebulae in Andromeda (M31): I. Imaging the disk and halo with MegaCam@CFHT. (arXiv:1903.02597v1 [astro-ph.GA])

The survey of Planetary Nebulae in Andromeda (M31): I. Imaging the disk and halo with MegaCam@CFHT. (arXiv:1903.02597v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Bhattacharya_S/0/1/0/all/0/1">Souradeep Bhattacharya</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Arnaboldi_M/0/1/0/all/0/1">Magda Arnaboldi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hartke_J/0/1/0/all/0/1">Johanna Hartke</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gerhard_O/0/1/0/all/0/1">Ortwin Gerhard</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Comte_V/0/1/0/all/0/1">Valentin Comte</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+McConnachie_A/0/1/0/all/0/1">Alan McConnachie</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Harris_W/0/1/0/all/0/1">William E. Harris</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Caldwell_N/0/1/0/all/0/1">Nelson Caldwell</a>

The Andromeda (M31) galaxy subtends nearly 100 sq. deg. on the sky, with
severe contamination from the Milky Way halo stars whose surface density
displays a steep gradient across the entire M31 field-of-view. Planetary
Nebulae (PNe) are a population of stars firmly associated with M31, that are
excellent tracers of light, chemistry and motion in galaxies. We present a 16
sq. deg. survey of the disk and inner halo of M31 with MegaCam@CFHT to identify
PNe, characterize their luminosity-specific PN number and luminosity function
(PNLF). PNe were identified based on their bright OIII 5007 $unicode{x212B}$
emission and absence of a continuum. Subsamples of the faint PNe were
independently confirmed by matching with resolved Hubble Space Telescope
sources from the PHAT survey and spectroscopic follow-up observations with
HectoSpec@MMT. The current survey reaches 2 mag fainter than the previous
most-sensitive survey. We identify 4289 PNe, of which only 1099 were previously
known. By comparing the PN number density with the surface brightness profile
of M31 out to ~30 kpc along the minor-axis, we find that the stellar population
in the inner halo has a 7 times larger luminosity-specific PN number value than
that of the disk. It indicates that the stellar population at deprojected
minor-axis radii larger than ~10 kpc is different from that in the M31 disk. We
measure the PNLF and find a bright cut-off and a slope consistent with the
previous determination by Ciardullo et al. (1989). Interestingly, it shows a
significant rise at the faint end, present in all radial bins covered by the
survey, much steeper than that observed for the Magellanic clouds and Milky Way
bulge. M31 shows two major episodes of star formation and the rise in the faint
end of the PNLF is possibly associated with the older stellar population. It
may also be a result of varying opacity of the PNe.

The Andromeda (M31) galaxy subtends nearly 100 sq. deg. on the sky, with
severe contamination from the Milky Way halo stars whose surface density
displays a steep gradient across the entire M31 field-of-view. Planetary
Nebulae (PNe) are a population of stars firmly associated with M31, that are
excellent tracers of light, chemistry and motion in galaxies. We present a 16
sq. deg. survey of the disk and inner halo of M31 with MegaCam@CFHT to identify
PNe, characterize their luminosity-specific PN number and luminosity function
(PNLF). PNe were identified based on their bright OIII 5007 $unicode{x212B}$
emission and absence of a continuum. Subsamples of the faint PNe were
independently confirmed by matching with resolved Hubble Space Telescope
sources from the PHAT survey and spectroscopic follow-up observations with
HectoSpec@MMT. The current survey reaches 2 mag fainter than the previous
most-sensitive survey. We identify 4289 PNe, of which only 1099 were previously
known. By comparing the PN number density with the surface brightness profile
of M31 out to ~30 kpc along the minor-axis, we find that the stellar population
in the inner halo has a 7 times larger luminosity-specific PN number value than
that of the disk. It indicates that the stellar population at deprojected
minor-axis radii larger than ~10 kpc is different from that in the M31 disk. We
measure the PNLF and find a bright cut-off and a slope consistent with the
previous determination by Ciardullo et al. (1989). Interestingly, it shows a
significant rise at the faint end, present in all radial bins covered by the
survey, much steeper than that observed for the Magellanic clouds and Milky Way
bulge. M31 shows two major episodes of star formation and the rise in the faint
end of the PNLF is possibly associated with the older stellar population. It
may also be a result of varying opacity of the PNe.

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