A%20Survey%20of%20Local%20Group%20Galaxies%20Currently%20Forming%20Stars

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A Survey of Local Group GalaxiesCurrently
Forming Stars
Phil Massey Lowell Observatory AAS January 2003
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The Team

• Paul Hodge, Univ. of Washington
• Shadrian Holmes, Univ. of Texas
• George Jacoby, WIYN
• Nichole King, Lowell Observatory
• Phil Massey (PI), Lowell Observatory
• Knut Olsen, CTIO/NOAO
• Abi Saha, KPNO/NOAO
• Chris Smith, CTIO/NOAO

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Our Science

• The galaxies of the Local Group serve as our
  laboratories for studying stellar evolution and
  star formation as a function of metallicity, Z.
  (Z varies by a factor of 17 from WLM to M31.)
• For massive stars, this is particularly
  important, as mass-loss rates are roughly
  proportional to Z0.5, and mass-loss greatly
  affects the evolution of massive stars.

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Relative number of red supergiants (RSGs) and
Wolf-Rayet stars (W-Rs)
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Our Science (continued)
Along the way well find The most massive
supergiants. Luminous Blue Variables and other
luminous stars with H? emission. Star formation
rates for massive stars. Distribution and
numbers of evolved massive stars (RSGs, WRs).
HII regions, the extent of the diffuse emission,,
SNRs, and planetary nebulae.
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Your Science

• This survey will provide the source list
  (finding charts) for spectroscopy with 8-10-m
  telescopes for decades to come. Our data
  products include
• Stacked images (UBVRI, H?, OIII, SII)
• Individual dithered images (suitable for
  photometry).
• Calibration
• Catalog of UBVRI photometry of roughly 10 million
  stars

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What Were Doing!

• Imaging with Mosaic CCD camera on KPNO and CTIO
  4-m telescopes of all the Local Group galaxies
  currently forming stars
• M31 (10 fields) Pegasus Dwarf
• M33 (3 fields) Phoenix
• IC 10 IC 1613
• NGC 6822 Sextans A
• WLM Sextans B

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What Were Doing (continued)

• Aiming for a S/N of 10 at UBVRI25,
• in 1 seeing
• Also imaging in H?, OIII, SII
• Each field 5 ditherings, then stacked.

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Hasnt All This Been Done Before?

• Yes, but not with our depth, area, photometric
  accuracy and resolution!
• Photographic plates had the area coverage and
  resolution, but not the photometric accuracy or
  depth.
• CCD studies had the depth and accuracy but not
  always the resolution and certainly not the area
  coverage.

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Comparison of M31 CCD Surveys
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Basic Processing
Generally following the Valdes IRAF pipeline
but with some enhancements. Details, and
software, can be found at our web site
http//www.lowell.edu/massey/lgsurvey
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Photometry

• For the purposes of photometry, we treat the
• Mosaic camera as 8 separate instruments
• PSF variations within a single chip modest
  compared to chip-to-chip variations.
• Different DQE-wavelength dependence for each chip
  means different color terms and even different
  zero-points (despite flat-fielding efforts.

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How weve solved the calibration problem
Anderson Mesa
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External Calibration using Lowell s 1.2-m Hall
Telescope

• Can use only the most pristine, photometric
  nights.
• Select the best calibrated Landolt standards
  covering a complete range of colors
• Investigate gravity effects on the U-band filter

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Progress Report---How are We Doing?

• All images for M31 (10 fields), M33 (3 fields),
  NGC 6822, IC10, WLM, Phoenix, Sextans A, and
  Sextans B are now released, and sitting in the
  NOAO NSA archive.
• Poor weather in early September prevented us from
  completing the project still need IC1613 and the
  Pegasus dwarf.
• Calibration in progress and catalog should be
  complete on schedule, release Jan 2004.

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Did We Achieve our 1.0 seeing goal?

• Not really...

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1.3
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0.76
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1.3
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0.76
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Poor seeing matters!

• To redo the images with seeing gt 1.5 would
  require only a few additional nights.

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M31 in 10 fields
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M31 in 10 fields
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M31 Fields 2 3
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M33-North
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M33-Center
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NGC 6822
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Phoenix
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WLM
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Whats Next?

• Spectroscopy!

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M31
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N206 in M31
ob78-231
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HST/ FUV ob78-231

• Bianchi, Hutchings, Massey (1996, AJ, 111, 2303)

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To take high S/N optical spectra at B19 requires
a really big telescope...
The 6.5-m MMT
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Optical (blue) spectrum ob78-231
Spectrum in collaboration with Kathy Eastwood
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OB78-231 at H?
Spectrum in collaboration with Kathy Eastwood