Baryons and Their Halos

Galaxies are composed of baryonic stars and gas embedded in dark matter halos. Here I briefly review two aspects of the connection between baryons and their halos. (1) The observed baryon content of galaxies falls short of the cosmic baryon fraction by an amount that varies systematically with mass. Where these missing baryons now reside is unclear. (2) The characteristic acceleration in disk galaxies correlates strongly with their baryonic mass surface density. This implies a close coupling between the gravitational dynamics, which is presumably dominated by dark matter, and the purely baryonic components of galaxies.Comment: 4 pages. Invited contribution to "Hunting for the Dark: The Hidden Side of Galaxy Formation", Malta, 19-23 Oct. 2009, eds. V.P. Debattista & C.C. Popescu, AIP Conf. Ser., in pres

Tracking citations and altmetrics for research data: Challenges and opportunities

Methods for determining research quality have long been debated but with little lasting agreement on standards, leading to the emergence of alternative metrics. Altmetrics are a useful supplement to traditional citation metrics, reflecting a variety of measurement points that give different perspectives on how a dataset is used and by whom. A positive development is the integration of a number of research datasets into the ISI Data Citation Index, making datasets searchable and linking them to published articles. Yet access to data resources and tracking the resulting altmetrics depend on specific qualities of the datasets and the systems where they are archived. Though research on altmetrics use is growing, the lack of standardization across datasets and system architecture undermines its generalizability. Without some standards, stakeholders' adoption of altmetrics will be limited

Predictions for the sky-averaged depth of the 21cm absorption signal at high redshift in cosmologies with and without non-baryonic cold dark matter

We consider the 21cm absorption signal expected at high redshift in cosmologies with and without non-baryonic cold dark matter. The expansion of the early universe decelerates strongly with dark matter, but approximately coasts without it. This results in a different path length across the epochs when absorption is expected, with the consequence that the absorption is predicted to be a factor of $\sim 2$ greater without dark matter than with it. Observation of such a signal would motivate consideration of extended theories of gravity in lieu of dark matter.Comment: Accepted for publication in Phys. Rev. Letters. 9 pages (4 of which are bibliography), 1 figure. Model data available at http://astroweb.case.edu/ssm/models

Hulk Smash”™ Busting the OAA Silo!

This poster focuses on Lavery Library’s collaboration with the Office of Academic Affairs, OAA. At St. John Fisher College students with learning disabilities testing accommodations take their exams in the library instead of a testing center. This is unique because OAA is located in another building from the library and therefore they have to coordinate scheduling of a proctor and student in room they do not control. The library also balances the needs of the general student population and the needs of OAA by offering students other study locations in the library while testing is in progress. The library then holds the testing materials along with testing accessories behind the checkout desk until proctor and student arrive. Communication is crucial for this to all happen smoothly. Over the last 2 years the number of students needing accommodations has significantly increased so the relationship between the library and OAA has gotten stronger out of necessity. Access Services staff continues the strong communication within the department to coordinate exams which happen after hours or on the weekends when the OAA office is closed. Since the library is open for more than 100 hours a week, faculty are allowed to drop off testing materials any hour we are open. Four permanent part-time employees and 20 work study students are all trained on the testing process; this facilitates student success by accommodating testing outside of business hours. The library and OAA have recently created a focus group to determine the future of testing on the Fisher campus

Some Systematic Properties of Rotation Curves

The rotation curves of spiral galaxies obey strong scaling relations. These include the Tully-Fisher and baryonic Tully-Fisher relations, and the mass discrepancy--acceleration relation. These relations can be used to place constraints on the mass-to-light ratios of stars. Once the stellar mass is constrained, the distribution of dark matter follows. The shape of the dark matter distribution is consistent with the expectations of NFW halos exterior to 1 kpc, but the amplitude is wrong. This is presumably related to the long-standing problem of the normalization of the Tully-Fisher relation and may imply a downturn in the amplitude of the power spectrum at small scales. More fundamentally, the persistent success of MOND remains a troubling fact.Comment: 8 pages including 7 figures. Invited review for the 21st IAP Colloquium: Mass Profiles and Shapes of Cosmological Structures, eds. G. A. Mamon, F. Combes, C. Deffayet, B. For

Predictions and Outcomes for the Dynamics of Rotating Galaxies

A review is given of a priori predictions made for the dynamics of rotating galaxies. One theory - MOND - has had many predictions corroborated by subsequent observations. While it is sometimes possible to offer post hoc explanations for these observations in terms of dark matter, it is seldom possible to use dark matter to predict the same phenomena.Comment: 36 pages (10 are references), 9 figures. Invited review for the Galaxies special Issue "Debate on the Physics of Galactic Rotation and the Existence of Dark Matter." Provides test cases for the importance of prior predictions in the application of the scientific metho