``ISO Observations of the Giant H II Regions in M 101''

   H. Dinerstein et al., in preparation



The following abstract is more for planning and internal (team)
purposes than for the actual paper. (I'll rewrite the abstract
when I finish the calculations and paper draft!) 



ABSTRACT:  We report observations with the ISO Long Wavelength
Spectrometer (LWS) of 3 giant H II regions (NGC 5447, NGC 5461,
and NGC 5471) in the spiral arms of the nearby Sc galaxy M 101,  
as well as the galaxy center and a number of inter-arm positions.
These H II region complexes are extraordinarily luminous,
some 10 times more luminous than the largest H II regions in
the Milky Way and M 33; they contain about 10^7 M_solar of 
ionized gas, and ionizing luminosities coresponding to several
hundreds of early type O stars. Using the LWS, we have measured
the [C II] 158 and [O I] 63 micron atomic cooling lines from
all four regions, and compare them them to the H alpha,
far-infrared continuum, CO, and radio continuum fluxes of
these complexes. M 101 is famous for having a particularly
strong radial abundance gradient, established from optical
spectroscopy of these very H II regions. Despite a difference
of about a factor of 5 in metallicity, the H II regions 
NGC 5461 and 5471 have similar dust temperatures and PDR
parameters as measured by ratios among the far-infrared lines
and thermal continuum, indicating that metallicity alone does
not dominate the energetics of H II region/PDR complexes.

We also observed the [N II] 122 and [O III] 88 micron
lines, arising from the ionized gas, in NGC 5447, NGC 5461,
and at the center.  We compare these to optical results; as
for NGC 604 in M33 (Dinerstein et al. 1987), they are consistent
with gas in the low-density limit.  We also address the 
properties of diffuse emission from ionized gas in the 
extended inner disk, using [C II] maps extending to several
arc minutes from the center. The radial fall-off of the [C II]
flux as seen by ISO is compared to other indicators of diffuse
ionized and atomic gas across the disk.


PRELIMINARY OUTLINE: 

1. Introduction: The Giant H II Regions of M 101 -  historical role
	and significance (distance scale calibrators, linchpins 
	for metallicity studies of extragalactic H II regions)

2. Observations
	2.1. LWS Targeted Observations (Key Project Data):
               motivation for selection of beam positions 
        2.2. LWS Auxiliary Data (public domain [C II] and
               [N II] spatial cuts): description of what
               was available and observing parameters 
        2.3. Observations at other wavelengths: Sangeeta's
               H-alpha images?; data at various wavelengths
               compiled from the literature

3. Reductions
        3.1. Considerations for the KP Data: special problem
               with dark current variations, how we handled it;
               >> IR continuum values are lost, but line fluxes robust
        3.2. Reductions of the archival data: monochromatic mapping
               or ``photometric'' mode, reduced by Jim B.
        3.3. Comparison to IRAS HiRes maps: beam matching;
               correction for flux outside (40-120 micron band),
               from George's dust emission models

4. Analysis and Results for the Giant H II Regions
        4.1. PDR Line Diagnostics: 158/63, (158+63)/FIR, ratios
                vs. 60/100 color etc. - compare to Kaufman & Hollenbach
                models, compare to distant sample overall trends
        4.2. Comparisons to CO data, radio data
        4.3. Comparisons to H+ Emission (H-alpha, IR lines?)

5. Global Issues
        5.1. Results in the context of the Metallicity Gradient
        5.2. Properties of the Extended Inner Disk of M 101:
                previous picture from radio continuum, CO, H-alpha
                results in the literature; ISO Observations and
                what they tell us
	5.3. Comparison to other, well-studied Galaxies (by ISO,
                KAO, e.g. M 51, M 33, etc.

6. Summary


							

Contributions (so far) from KP Team Members:
-----------------------------------
  Collection and reduction of archival (non-KP) LWS data: Jim Brauher

  Examination of IRAS Hi-Res maps for continuum fluxes: Danny Dale

  Original planning of mapping strategy: Steve Lord

  H-alpha imaging at Palomar: Sangeeta 

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