394 research outputs found
A Search for Ionized Gas in the Draco and Ursa Minor Dwarf Spheroidal Galaxies
The Wisconsin H Alpha Mapper has been used to set the first deep upper limits
on the intensity of diffuse H alpha emission from warm ionized gas in the Local
Group dwarf spheroidal galaxies (dSphs) Draco and Ursa Minor. Assuming a
velocity dispersion of 15 km/s for the ionized gas, we set limits for the H
alpha intensity of less or equal to 0.024 Rayleighs and less or equal to 0.021
Rayleighs for the Draco and Ursa Minor dSphs, respectively, averaged over our 1
degree circular beam. Adopting a simple model for the ionized interstellar
medium, these limits translate to upper bounds on the mass of ionized gas of
approximately less than 10% of the stellar mass, or approximately 10 times the
upper limits for the mass of neutral hydrogen. Note that the Draco and Ursa
Minor dSphs could contain substantial amounts of interstellar gas, equivalent
to all of the gas injected by dying stars since the end of their main star
forming episodes more than 8 Gyr in the past, without violating these limits on
the mass of ionized gas.Comment: 10 pages, 2 figures, AASTeX two-column format. Accepted for
publication in The Astrophysical Journa
Buoyant Venus station mission feasibility study for 1972 and 1973 launch opportunities. Volume 3 - Configuration definition. Part 2 - Appendixes Final report
Buoyant Venus station mission study for 1972 - 1973 launch period - backup data including atmospheric models, heat shield requirements, etc
The Star Clusters in the Starburst Irregular Galaxy NGC 1569
We examine star clusters in the irregular, starburst galaxy NGC 1569 from HST
images. In addition to the two known super star clusters, we identify 45 other
clusters that are compact but resolved. Integrated UVI colors of the clusters
span a large range, and suggest that ages range from 3 Myrs to 1 Gyr. However,
most of the clusters were formed at the tail end of the recent starburst.
Numerous clusters in addition to the know super star clusters are similar in
luminosity to a small globular cluster. We examined the radial surface
brightness of four of the clusters. Their half-light radii and core radii are
in the range observed in present-day globular clusters. Therefore, conditions
that produced the recent starburst have also been those necessary for producing
compact, bright star clusters.
We examine resolved stars in the outer parts of the two super star clusters.
Cluster A is dominated by bright blue stars with a small population of red
supergiants. Sub-components A1 and A2 have similar colors and a two-dimensional
color map does not offer evidence that one component is dominated by red
supergiants and the other not. The contradiction of the presence of red super-
giants with Wolf-Rayet stars may instead not be a contradiction at all since
there coexistence in a coeval population is not inconsistent with the evolution
of massive stars. Cluster B is dominated by red supergiants, and this is
confirmed by the presence of the stellar CO absorption feature in an integrated
spectrum. The various age indicators are consistent with a picture in which
cluster B is of order 10--20 Myrs old, and cluster A is >4-5 Myrs old.Comment: To be published in AJ, November 200
Blue Straggler Stars: Early Observations that Failed to Solve the Problem
In this chapter, I describe early ideas on blue stragglers, and various
observations (some published, some not) that promised but failed to resolve the
question of their origin. I review the data and ideas that were circulating
from Allan Sandage's original discovery in 1953 of "anomalous blue stars" in
the globular cluster M3, up until about 1992, when what seems to have been the
only previous meeting devoted to Blue Straggler Stars (BSSs) was held at the
Space Telescope Science Institute.Comment: Chapter 2, in Ecology of Blue Straggler Stars, H.M.J. Boffin, G.
Carraro & G. Beccari (Eds), Astrophysics and Space Science Library, Springe
Owyhee Russet: AVariety with High Yields of U.S. No. 1 Tubers, Excellent Processing Quality, and Moderate Resistance to Fusarium Dry Rot (\u3ci\u3eFusarium solani var. coeruleum\u3c/i\u3e)
Owyhee Russet (AO96160-3) originated from a cross between A89384-10 and A89512-3 in 1996. Owyhee Russet was released in 2009 by Oregon State University, in cooperation with the USDA-ARS and the Agricultural Experiment Stations of Idaho and Washington and is a product of the Northwest Potato Variety (Tri-State) Development Program. Owyhee Russet has semi-erect medium sized vines with medium to late maturity. The tubers are long, with a tan skin, medium russeting, and attractive tuber appearance for fresh market. Owyhee Russet was evaluated in several locations across the Northwest for more than 15 years. Total yield of Owyhee Russet is similar to that of Russet Burbank and Ranger Russet but significantly higher than Russet Norkotah. U.S. No.1 tuber yield of Owyhee Russet is significantly higher than Russet Burbank and Russet Norkotah, resulting in substantially higher marketable yield. Owyhee Russet tubers have significantly higher specific gravity than Russet Burbank and Russet Norkotah. Fry color following tuber storage at 4°C and 9°C is significantly lighter for Owyhee Russet than the comparison varieties. Relative strengths include high yield with a very high proportion of U.S. No.1 tubers, good tuber appearance and excellent processing quality, resistance to cold sweetening, common scab and Fusarium dry rot. Weaknesses include susceptibility to foliar and tuber late blight and susceptibility to metribuzin herbicide injury. Allelic patterns of five SSR markers have shown that Owyhee Russet has a distinctive DNA genetic fingerprint from its russet type reference varieties which are Ranger Russet, Russet Burbank, and Russet Norkotah
The Dynamical Equilibrium of Galaxy Clusters
If a galaxy cluster is effectively in dynamical equilibrium then all galaxy
populations within the cluster must have distributions in velocity and position
that individually reflect the same underlying mass distribution, although the
derived virial masses can be quite different. Specifically, within the CNOC
cluster sample the virial radius of the red galaxy population is, on the
average, a factor of smaller than that of the blue population.
The red galaxies also have a smaller RMS velocity dispersion, a factor of within our sample. Consequently, the virial mass calculated from the
blue galaxies is times larger than from the red galaxies.
However, applying the Jeans equation of stellar-hydrodynamical equilibrium to
the red and blue subsamples separately give statistically identical cluster
mass profiles. This is strong evidence that these clusters are effectively
equilibrium systems, and therefore empirically demonstrates that the masses in
the virialized region are reliably estimated using dynamical techniques.Comment: Submitted for publication in ApJLetts. 12 pages as a uufile, also
available at http://manaslu.astro.utoronto.ca/~carlberg/cnoc/br/br.ps.g
Exploring Spirituality in Teaching Within a Christian School Context Through Collaborative Action Research
This article reports on a collaborative action research project conducted in New Zealand, during 2012, exploring spirituality in teaching within a Christian school context. The experienced primary school teacher participant chose to take action around the issue of personal fear and insecurity which were believed to be hindering professional growth and relationships. Through self-directed inquiry, critical reflective journaling, Bible study, fellowship and prayer with trusted friends, the teacher experienced a renewed sense of peace and freedom in Christ. This personal transformation was believed to be influential on subsequent professional practice, assisting the teacher to become more relational, responsive and compassionate. The findings provide a rich description of the participantâs spirituality, the lived reality of a personâs spiritual life. This report will be of interest to teachers, teacher-leaders and teacher-educators who desire to explore Christian spirituality through practitioner-led inquiry
SMC in space and time: a project to study the evolution of the prototype interacting late-type dwarf galaxy
We introduce the SMC in space and time, a large coordinated space and ground-based program to study star formation processes and history, as well as variable stars, structure, kinematics and chemical evolution of the whole SMC. Here, we present the Colour-Magnitude Diagrams (CMDs) resulting from HST/ACS photometry, aimed at deriving the star formation history (SFH) in six fields of the SMC. The fields are located in the central regions, in the stellar halo, and in the wing toward the LMC. The CMDs are very deep, well beyond the oldest Main Sequence Turn-Off, and will allow us to derive the SFH over the entire Hubble tim
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