2,029 research outputs found
Response to Draft Recommendations for Health System Reform
The final report of the Maine Health Care Reform Commission (MHCRC) was submitted to Governor Angus King in November, 1995. Given the complexity of what we call the healthcare system as well as the moving targets of federal and state incentives for reform, the report accomplished a great deal in a short period of time. Commission members were mandated to offer a single payer universal coverage bill, a multiple payer universal coverage bill, and a bill to achieve reform through incremental changes to the existing system, emphasizing cost containment, managed care, and improved access. The commission was also mandated to cost out its recommendations Reactions to the MHCRC report were invited from individuals who represent constituencies which often have an influential role in healthcare. Five commentaries address pros and cons of particular elements of the commission’s report. Dale Gordon and Kim Boothby-Ballantyne offer a nursing perspective in this commentary
Star-Forming or Starbursting? The Ultraviolet Conundrum
Compared to starburst galaxies, normal star forming galaxies have been shown
to display a much larger dispersion of the dust attenuation at fixed reddening
through studies of the IRX-beta diagram (the IR/UV ratio "IRX" versus the UV
color "beta"). To investigate the causes of this larger dispersion and attempt
to isolate second parameters, we have used GALEX UV, ground-based optical, and
Spitzer infrared imaging of 8 nearby galaxies, and examined the properties of
individual UV and 24 micron selected star forming regions. We concentrated on
star-forming regions, in order to isolate simpler star formation histories than
those that characterize whole galaxies. We find that 1) the dispersion is not
correlated with the mean age of the stellar populations, 2) a range of dust
geometries and dust extinction curves are the most likely causes for the
observed dispersion in the IRX-beta diagram 3) together with some potential
dilution of the most recent star-forming population by older unrelated bursts,
at least in the case of star-forming regions within galaxies, 4) we also
recover some general characteristics of the regions, including a tight positive
correlation between the amount of dust attenuation and the metal content.
Although generalizing our results to whole galaxies may not be immediate, the
possibility of a range of dust extinction laws and geometries should be
accounted for in the latter systems as well.Comment: 18 pages, 17 figures, accepted for publication in Ap
The Spitzer Local Volume Legacy: Survey Description and Infrared Photometry
The survey description and the near-, mid-, and far-infrared flux properties
are presented for the 258 galaxies in the Local Volume Legacy (LVL). LVL is a
Spitzer Space Telescope legacy program that surveys the local universe out to
11 Mpc, built upon a foundation of ultraviolet, H-alpha, and HST imaging from
11HUGS (11 Mpc H-alpha and Ultraviolet Galaxy Survey) and ANGST (ACS Nearby
Galaxy Survey Treasury). LVL covers an unbiased, representative, and
statistically robust sample of nearby star-forming galaxies, exploiting the
highest extragalactic spatial resolution achievable with Spitzer. As a result
of its approximately volume-limited nature, LVL augments previous Spitzer
observations of present-day galaxies with improved sampling of the
low-luminosity galaxy population. The collection of LVL galaxies shows a large
spread in mid-infrared colors, likely due to the conspicuous deficiency of 8um
PAH emission from low-metallicity, low-luminosity galaxies. Conversely, the
far-infrared emission tightly tracks the total infrared emission, with a
dispersion in their flux ratio of only 0.1 dex. In terms of the relation
between infrared-to-ultraviolet ratio and ultraviolet spectral slope, the LVL
sample shows redder colors and/or lower infrared-to-ultraviolet ratios than
starburst galaxies, suggesting that reprocessing by dust is less important in
the lower mass systems that dominate the LVL sample. Comparisons with
theoretical models suggest that the amplitude of deviations from the relation
found for starburst galaxies correlates with the age of the stellar populations
that dominate the ultraviolet/optical luminosities.Comment: Accepted for publication in ApJ; Figures 1,8,9 provided as jpeg
Modeling Dust and Starlight in Galaxies Observed by Spitzer and Herschel: NGC 628 and NGC 6946
We characterize the dust in NGC628 and NGC6946, two nearby spiral galaxies in
the KINGFISH sample. With data from 3.6um to 500um, dust models are strongly
constrained. Using the Draine & Li (2007) dust model, (amorphous silicate and
carbonaceous grains), for each pixel in each galaxy we estimate (1) dust mass
surface density, (2) dust mass fraction contributed by polycyclic aromatic
hydrocarbons (PAH)s, (3) distribution of starlight intensities heating the
dust, (4) total infrared (IR) luminosity emitted by the dust, and (5) IR
luminosity originating in regions with high starlight intensity. We obtain maps
for the dust properties, which trace the spiral structure of the galaxies. The
dust models successfully reproduce the observed global and resolved spectral
energy distributions (SEDs). The overall dust/H mass ratio is estimated to be
0.0082+/-0.0017 for NGC628, and 0.0063+/-0.0009 for NGC6946, consistent with
what is expected for galaxies of near-solar metallicity. Our derived dust
masses are larger (by up to a factor 3) than estimates based on
single-temperature modified blackbody fits. We show that the SED fits are
significantly improved if the starlight intensity distribution includes a
(single intensity) "delta function" component. We find no evidence for
significant masses of cold dust T<12K. Discrepancies between PACS and MIPS
photometry in both low and high surface brightness areas result in large
uncertainties when the modeling is done at PACS resolutions, in which case
SPIRE, MIPS70 and MIPS160 data cannot be used. We recommend against attempting
to model dust at the angular resolution of PACS.Comment: To be published in Apj, September 2012. See the full version at
http://www.astro.princeton.edu/~ganiano/Papers
Mid-Infrared Spectral Measures of Star-Formation and AGN Activity in Normal Galaxies
We investigate the use of MIR PAH bands, continuum and emission lines as
probes of star-formation and AGN activity in a sample of 100 'normal' and local
(z~0.1) emission-line galaxies. The MIR spectra were obtained with the Spitzer
Space Telescope Infrared Spectrograph (IRS) as part of the Spitzer-SDSS-GALEX
Spectroscopic Survey (SSGSS) which includes multi-wavelength photometry from
the UV to the FIR and optical spectroscopy. The continuum and features were
extracted using PAHFIT (Smith et al. 2007), a decomposition code which we find
to yield PAH equivalent widths up to ~30 times larger than the commonly used
spline methods. Despite the lack of extreme objects in our sample (such as
strong AGNs, low metallicity galaxies or ULIRGs), we find significant
variations in PAH, continuum and emission line properties and systematic trends
between these MIR properties and optically derived physical properties such as
age, metallicity and radiation field hardness. We revisit the diagnostic
diagram relating PAH equivalent widths and [Ne II]12.8micrometers/[O
IV]25.9micrometers line ratios and find it to be in much better agreement with
the standard optical star-formation/AGN classification than when spline
decompositions are used, while also potentially revealing obscured AGNs. The
luminosity of individual PAH components, of the continuum, and with poorer
statistics, of the neon emission lines and molecular hydrogen lines, are found
to be tightly correlated to the total IR luminosity, making individual MIR
components good gauges of the total dust emission in SF galaxies. Like the
total IR luminosity, these individual components can be used to estimate dust
attenuation in the UV and in Halpha lines based on energy balance arguments. We
also propose average scaling relations between these components and dust
corrected, Halpha derived star-formation rates.Comment: Accepted for publication in Ap
Dust Emission from Evolved and Unevolved HII Regions in the Large Magellanic Cloud
We present a study of the dust properties of 12 classical and superbubble HII
regions in the Large Magellanic Cloud. We use infrared photometry from Spitzer
(8, 24, 70, and 160 \mum bands), obtained as part of the Surveying the Agents
of a Galaxy's Evolution (SAGE) program, along with archival spectroscopic
classifications of the ionizing stars to examine the role of stellar sources on
dust heating and processing. Our infrared observations show surprisingly little
correlation between the emission properties of the dust and the effective
temperatures or bolometric magnitudes of stars in the HII regions, suggesting
that the HII region evolutionary timescale is not on the order of the dust
processing timescale. We find that the infrared emission of superbubbles and
classical HII regions shows little differentiation between the two classes,
despite the significant differences in age and morphology. We do detect a
correlation of the 24 \mum emission from hot dust with the ratio of 70 to 160
\mum flux. This correlation can be modeled as a trend in the temperature of a
minority hot dust component, while a majority of the dust remains significantly
cooler.Comment: 15 pages, 5 figures. Accepted to Ap
Spitzer Observations of Cold Dust Galaxies
We combine new Spitzer Space Telescope observations in the mid- and
far-infrared with SCUBA 850 micron observations to improve the measurement of
dust temperatures, masses and luminosities for 11 galaxies of the SCUBA Local
Universe Galaxy Survey (SLUGS). By fitting dust models we measure typical dust
masses of 10E7.9 M_sol and dust luminosities of ~ 10E10 L_sol, for galaxies
with modest star formation rates. The data presented in this paper combined
with previous observations show that cold dust is present in all types of
spiral galaxies and is a major contributor to their total luminosity. Because
of the lower dust temperature of the SCUBA sources measured in this paper, they
have flatter Far-IR nu F_nu(160um)/nu F_nu(850um) slopes than the larger
Spitzer Nearby Galaxies Survey (SINGS), the sample that provides the best
measurements of the dust properties of galaxies in the nearby universe. The new
data presented here added to SINGS extend the parameter space that is well
covered by local galaxies, providing a comprehensive set of templates that can
be used to interpret the observations of nearby and distant galaxies.Comment: Accepted by A.J. 16 pages, 10 figures, 7 tables. High resolution
version at http://mips.as.arizona.edu/~cnaw/slugs_hires.pd
A Multi-wavelength analysis of M81: insight on the nature of Arp's loop
Context: The optical ring like structure detected by Arp (1965) around M81
(commonly referenced as "Arp's loop") represents one of the most spectacular
feature observed in nearby galaxies. Arp's loop is commonly interpreted as a
tail resulting from the tidal interaction between M81 and M82. However, since
its discovery the nature of this feature has remained controversial. Aims: Our
primary purpose was to identify the sources of optical and infrared emission
observed in Arp's loop. Methods: The morphology of the Arp's loop has been
investigated with deep wide-field optical images. We also measured its colors
using IRAS and Spitzer-MIPS infrared images and compared them with those of the
disk of M81 and Galactic dust cirrus that fills the area where M81 is located.
Results: Optical images reveal that this peculiar object has a filamentary
structure characterized by many dust features overlapping M81's field. The
ratios of far-infrared fluxes and the estimated dust-to-gas ratios indicate the
infrared emission of Arp's loop is dominated by the contribution of cold dust
that is most likely from Galactic cirrus. Conclusions: The above results
suggest that the light observed at optical wavelengths is a combination of
emission from i) a few recent star forming regions located close to M81, where
both bright UV complexes and peaks in the HI distribution are found, ii) the
extended disk of M81 and iii) scattered light from the same Galactic cirrus
that is responsible for the bulk of the far infrared emission.Comment: 7 pages, 7 figures, accepted for publication by A&
The Spectral Energy Distribution of Dust Emission in the Edge-on spiral galaxy NGC 4631 as seen with Spitzer and the James Clerk Maxwell telescope
We explore variations in dust emission within the edge-on Sd spiral galaxy NGC 4631 using 3.6-160 μm Spitzer Space Telescope data and 450-850 μm JCMT data with the goals of understanding the relation between PAHs and dust emission, studying the variations in the colors of the dust emission, and searching for possible excess submillimeter emission compared to what is expected from dust models extrapolated from far-infrared wavelengths. The 8 μm PAH emission correlates best with 24 μm hot dust emission on 1.7 kpc scales, but the relation breaks down on 650 pc scales, possibly because of differences in the mean free paths between photons that excite the PAHs and photons that heat the dust and possibly because the PAHs are destroyed by the hard radiation fields within some star formation regions. The ratio of 8 μm PAH emission to 160 μm cool dust emission appears to vary as a function of radius. The 70 μm/160 μm and 160 μm/450 μm flux density ratios are remarkably constant even though the surface brightnesses vary by factors of 25, which suggests that the emission is from dust heated by a nearly uniform radiation field. Globally, we find an excess of 850-1230 μm emission relative to what would be predicted by dust models. The 850 μm excess is highest in regions with low 160 μm surface brightnesses, although the magnitude depends on the model fit to the data. We rule out variable emissivity functions or ~4 K dust as the possible origins of this 850 μm emission, but we do discuss the other possible mechanisms that could produce the emission
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