970 research outputs found
The Revealing Dust: Mid-Infrared Activity in Hickson Compact Group Galaxy Nuclei
We present a sample of 46 galaxy nuclei from 12 nearby (z<4500 km/s) Hickson
Compact Groups (HCGs) with a complete suite of 1-24 micron 2MASS+Spitzer
nuclear photometry. For all objects in the sample, blue emission from stellar
photospheres dominates in the near-IR through the 3.6 micron IRAC band.
Twenty-five of 46 (54%) galaxy nuclei show red, mid-IR continua characteristic
of hot dust powered by ongoing star formation and/or accretion onto a central
black hole. We introduce alpha_{IRAC}, the spectral index of a power-law fit to
the 4.5-8.0 micron IRAC data, and demonstrate that it cleanly separates the
mid-IR active and non-active HCG nuclei. This parameter is more powerful for
identifying low to moderate-luminosity mid-IR activity than other measures
which include data at rest-frame lambda<3.6 micron that may be dominated by
stellar photospheric emission. While the HCG galaxies clearly have a bimodal
distribution in this parameter space, a comparison sample from the Spitzer
Nearby Galaxy Survey (SINGS) matched in J-band total galaxy luminosity is
continuously distributed. A second diagnostic, the fraction of 24 micron
emission in excess of that expected from quiescent galaxies, f_{24D}, reveals
an additional 3 nuclei to be active at 24 micron. Comparing these two mid-IR
diagnostics of nuclear activity to optical spectroscopic identifications from
the literature reveals some discrepancies, and we discuss the challenges of
distinguishing the source of ionizing radiation in these and other lower
luminosity systems. We find a significant correlation between the fraction of
mid-IR active galaxies and the total HI mass in a group, and investigate
possible interpretations of these results in light of galaxy evolution in the
highly interactive system of a compact group environment.Comment: 20 pages, 17 figures (1 color), uses emulateapj. Accepted for
publication by Ap
Star Clusters in the Tidal Tails of Interacting Galaxies: Cluster Populations Across a Variety of Tail Environments
We have searched for compact stellar structures within 17 tidal tails in 13
different interacting galaxies using F606W- and F814W- band images from the
Wide Field Planetary Camera 2 (WFPC2) on the Hubble Space Telescope (HST). The
sample of tidal tails includes a diverse population of optical properties,
merging galaxy mass ratios, HI content, and ages. Combining our tail sample
with Knierman et al. (2003), we find evidence of star clusters formed in situ
with Mv < -8.5 and V-I < 2.0 in 10 of 23 tidal tails; we are able to identify
cluster candidates to Mv = -6.5 in the closest tails. Three tails offer clear
examples of "beads on a string" star formation morphology in V-I color maps.
Two tails present both tidal dwarf galaxy (TDG) candidates and cluster
candidates. Statistical diagnostics indicate that clusters in tidal tails may
be drawn from the same power-law luminosity functions (with logarithmic slopes
~ -2 - -2.5) found in quiescent spiral galaxies and the interiors of
interacting systems. We find that the tail regions with the largest number of
observable clusters are relatively young (< 250 Myr old) and bright (V < 24 mag
arcsec^(-2)), probably attributed to the strong bursts of star formation in
interacting systems soon after periapse. Otherwise, we find no statistical
difference between cluster-rich and cluster-poor tails in terms of many
observable characteristics, though this analysis suffers from complex,
unresolved gas dynamics and projection effects.Comment: Accepted for publication in the Astrophysical Journal. 27 pages, 8
figure
New Evidence of the Lower Miocene Age of the Blacktail Deer Creek Formation in Montana
193-204http://deepblue.lib.umich.edu/bitstream/2027.42/48250/2/ID089.pd
Principles And Practices Fostering Inclusive Excellence: Lessons From The Howard Hughes Medical Institute’s Capstone Institutions
Best-practices pedagogy in science, technology, engineering, and mathematics (STEM) aims for inclusive excellence that fosters student persistence. This paper describes principles of inclusivity across 11 primarily undergraduate institutions designated as Capstone Awardees in Howard Hughes Medical Institute’s (HHMI) 2012 competition. The Capstones represent a range of institutional missions, student profiles, and geographical locations. Each successfully directed activities toward persistence of STEM students, especially those from traditionally underrepresented groups, through a set of common elements: mentoring programs to build community; research experiences to strengthen scientific skill/identity; attention to quantitative skills; and outreach/bridge programs to broaden the student pool. This paper grounds these program elements in learning theory, emphasizing their essential principles with examples of how they were implemented within institutional contexts. We also describe common assessment approaches that in many cases informed programming and created traction for stakeholder buy-in. The lessons learned from our shared experiences in pursuit of inclusive excellence, including the resources housed on our companion website, can inform others’ efforts to increase access to and persistence in STEM in higher education
Older adults place lower value on choice relative to young adults
Choice is highly valued in modern society, from the supermarket to the hospital; however, it remains unknown
whether older and younger adults place the same value on increased choice. The current investigation tested
whether 53 older ( M age = 75.44 years) versus 53 younger adults ( M age = 19.58 years) placed lower value on increased
choice by examining the monetary amounts they were willing to pay for increased prescription drug coverage
options — important given the recently implemented Medicare prescription drug program. Results indicate
that older adults placed lower value on increasing choice sets relative to younger adults, who placed progressively
higher value on increasingly larger choice sets. These results are discussed regarding their implications for theory
and policy
U.S. GLOBAL CHANGE RESEARCH PROGRAM CLIMATE SCIENCE SPECIAL REPORT (CSSR)
Fifth-Order Draft
Table of Contents
Front Matter
About This Report........................................................................................ 1
Guide to the Report......................................................................................4
Executive Summary ................................................................................... 12
Chapters
1. Our Globally Changing Climate .......................................................... 38
2. Physical Drivers of Climate Change ................................................... 98
3. Detection and Attribution of Climate Change .................................... 160
4. Climate Models, Scenarios, and Projections .................................... 186
5. Large-Scale Circulation and Climate Variability ................................ 228
6. Temperature Changes in the United States ...................................... 267
7. Precipitation Change in the United States ......................................... 301
8. Droughts, Floods, and Hydrology ......................................................... 336
9. Extreme Storms ....................................................................................... 375
10. Changes in Land Cover and Terrestrial Biogeochemistry ............ 405
11. Arctic Changes and their Effects on Alaska and the Rest of the United States..... 443
12. Sea Level Rise ....................................................................................... 493
13. Ocean Acidification and Other Ocean Changes .............................. 540
14. Perspectives on Climate Change Mitigation .................................... 584
15. Potential Surprises: Compound Extremes and Tipping Elements .......... 608
Appendices
A. Observational Datasets Used in Climate Studies ............................. 636
B. Weighting Strategy for the Fourth National Climate Assessment ................ 642
C. Detection and Attribution Methodologies Overview ............................ 652
D. Acronyms and Units ................................................................................. 664
E. Glossary ...................................................................................................... 66
U.S. GLOBAL CHANGE RESEARCH PROGRAM CLIMATE SCIENCE SPECIAL REPORT (CSSR)
Fifth-Order Draft
Table of Contents
Front Matter
About This Report........................................................................................ 1
Guide to the Report......................................................................................4
Executive Summary ................................................................................... 12
Chapters
1. Our Globally Changing Climate .......................................................... 38
2. Physical Drivers of Climate Change ................................................... 98
3. Detection and Attribution of Climate Change .................................... 160
4. Climate Models, Scenarios, and Projections .................................... 186
5. Large-Scale Circulation and Climate Variability ................................ 228
6. Temperature Changes in the United States ...................................... 267
7. Precipitation Change in the United States ......................................... 301
8. Droughts, Floods, and Hydrology ......................................................... 336
9. Extreme Storms ....................................................................................... 375
10. Changes in Land Cover and Terrestrial Biogeochemistry ............ 405
11. Arctic Changes and their Effects on Alaska and the Rest of the United States..... 443
12. Sea Level Rise ....................................................................................... 493
13. Ocean Acidification and Other Ocean Changes .............................. 540
14. Perspectives on Climate Change Mitigation .................................... 584
15. Potential Surprises: Compound Extremes and Tipping Elements .......... 608
Appendices
A. Observational Datasets Used in Climate Studies ............................. 636
B. Weighting Strategy for the Fourth National Climate Assessment ................ 642
C. Detection and Attribution Methodologies Overview ............................ 652
D. Acronyms and Units ................................................................................. 664
E. Glossary ...................................................................................................... 66
- …