The Luminosity Distribution of Local Group Galaxies

From a rediscussion of Local Group membership, and of distances to individual galaxies, we obtain $M_V$ values for 35 probable and possible Local Group members. The luminosity function of these objects is well fitted by a Schechter function with faint end slope $\alpha = -1.1 \pm 0.1$. The probability that the luminosity distribution of the Local Group is a single Schechter function with $\alpha$ steeper than -1.3 is less than 1 per cent. However, more complicated luminosity functions, such as multi-component Schechter functions with steep faint-end slopes, cannot be ruled out. There is some evidence that the luminosity distribution of dwarf spheroidal galaxies in the Local Group is steeper than that of dwarf irregular galaxies.Comment: 13 pages, 2 figures, accepted for publication in The Astronomical Journal. Figure 2 replaced, conclusion based on this figure change

A Simple Character for Sex Differentiation of Pupae and Pupil Exuviae of the Dogwood Borer (Lepidoptera: Sesiidae)

The sex of dogwood borer pupae and pupal exuviae can be easily differentiated based on characteristics of the fused terminal abdominal segment. In males, it is composed of segments 8- 10 and has three distinct rows of posteriorly projecting spines. By contrast, in females, the fused terminal abdominal segment is composed of segments 7-10 and has four distinct rows of posteriorly projecting spines

Supernova Properties from Shock Breakout X-rays

We investigate the potential of the upcoming LOBSTER space observatory (due circa 2009) to detect soft X-ray flashes from shock breakout in supernovae, primarily from Type II events. LOBSTER should discover many SN breakout flashes, although the number is sensitive to the uncertain distribution of extragalactic gas columns. X-ray data will constrain the radii of their progenitor stars far more tightly than can be accomplished with optical observations of the SN light curve. We anticipate the appearance of blue supergiant explosions (SN 1987A analogs), which will uncover a population of these underluminous events. We consider also how the mass, explosion energy, and absorbing column can be constrained from X-ray observables alone and with the assistance of optically-determined distances. These conclusions are drawn using known scaling relations to extrapolate, from previous numerical calculations, the LOBSTER response to explosions with a broad range of parameters. We comment on a small population of flashes with 0.2 < z < 0.8 that should exist as transient background events in XMM, Chandra, and ROSAT integrations.Comment: 14 pages, 9 figures, accepted by MNRAS, presented at AAS 203rd meetin

On the Nature of the NGC 1275 System

Sub-arcsecond images, taken in B, R, and H-Alpha filters, and area spectroscopy obtained with the WIYN 3.5-m telescope provide the basis for an investigation of the unusual structures in the stellar body and ionized gas in and around the Perseus cluster central galaxy, NGC 1275. Our H-Alpha filter is tuned to gas at the velocity of NGC 1275, revealing complex, probably unresolved, small-scale features in the extended ionized gas, located up to 50/h kpc from NGC 1275. The mean H-Alpha surface brightness varies little along the outer filaments; this, together with the complex excitation state demonstrated by spectra, imply that the filaments are likely to be tubes, or ribbons, of gas. The morphology, location and inferred physical parameters of the gas in the filaments are consistent with a model whereby the filaments form through compression of the intracluster gas by relativistic plasma emitted from the active nucleus of NGC 1275. Imaging spectroscopy with the Densepak fiber array on WIYN suggests partial rotational support of the inner component of low velocity ionized gas. We confirm and extend evidence for features in the stellar body of NGC 1275, and identify outer stellar regions containing very blue, probably very young, star clusters. We interpret these as evidence for recent accretion of a gas-rich system, with subsequent star formation. We suggest that two main processes, which may be causally connected, are responsible for the rich phenomenology of the NGC 1275 system -- NGC 1275 experienced a recent merger/interaction with a group of gas-rich galaxies, and recent outflows from its AGN have compressed the intracluster gas, and perhaps the gas in the infalling galaxies, to produce a complex web of filaments. (Abridged)Comment: AJ, accepted; a recommended full resolution version is available at http://www.astro.wisc.edu/~chris/pera.p

Hubble Space Telescope WFPC-2 Imaging of Cassiopeia A

The young SNR Cassiopeia A was imaged with WFPC-2 through four filters selected to capture the complete velocity range of the remnant's main shell in several important emission lines. Primary lines detected were [O III] 4959,5007, [N II] 6583, [S II] 6716,6731 + [O II] 7319,7330 + [O I] 6300,6364, and [S III] 9069,9532. About 3/4th of the remnant's main shell was imaged in all four filters. Considerable detail is observed in the reverse-shocked ejecta with typical knot scale lengths of 0.2"-0.4" (1 - 2 x 10^16 cm). Both bright and faint emission features appear highly clumped. Large differences in [S III] and [O III] line intensities indicating chemical abundance differences are also seen, particularly in knots located along the bright northern limb and near the base of the northeast jet. A line of curved overlapping filament in the remnant's northwestern rim appears to mark the location of the remnant's reverse shock front in this region. Finger-like ejecta structures elsewhere suggest cases where the reverse shock front is encountering the remnant's clumped ejecta. Narrow-band [N II] images of the remnant's circumstellar knots ("QSFs") reveal them to be 0.1"-0.6" thick knots and filaments, often with diffuse edges facing away from the center of expansion. Three color composite images of the whole remnant and certain sections along with individual filter enlargements of selected regions of the bright optical shell are presented and discussed.Comment: 26 pages, 12 figures Accepted to the Astronomical Journa

Integrated Conceptual Ecosystem Model Development for the Southeast Florida Coastal Marine Ecosystem

The overall goal of the MARES (MARine and Estuarine goal Setting) project for South Florida is “to reach a science-based consensus about the defining characteristics and fundamental regulating processes of a South Florida coastal marine ecosystem that is both sustainable and capable of providing the diverse ecosystem services upon which our society depends.” Through participation in a systematic process of reaching such a consensus, science can contribute more directly and effectively to the critical decisions being made both by policy makers and by natural resource and environmental management agencies. The document that follows briefly describes MARES overall and this systematic process. It then describes in considerable detail the resulting output from the first step in the process, the development of an Integrated Conceptual Ecosystem Model (ICEM) for the third subregion to be addressed by MARES, the Southeast Florida Coast (SEFC). What follows with regard to the SEFC relies upon the input received from more than 60 scientists, agency resource managers, and representatives of environmental organizations during workshops held throughout 2009–2012 in South Florida

Shaping the Development of Prejudice: Latent Growth Modeling of the Influence of Social Dominance Orientation on Outgroup Affect in Youth

Social dominance orientation (SDO) has been theorized as a stable, early-emerging trait influencing outgroup evaluations, a view supported by evidence from cross-sectional and two-wave longitudinal research. Yet, the limitations of identifying causal paths with cross-sectional and two-wave designs are increasingly being acknowledged. This article presents the first use of multi-wave data to test the over-time relationship between SDO and outgroup affect among young people. We use cross-lagged and latent growth modeling (LGM) of a three-wave data set employing Norwegian adolescents (over 2 years, N = 453) and a five-wave data set with American university students (over 4 years, N = 748). Overall, SDO exhibits high temporal rank-order stability and predicts changes in outgroup affect. This research represents the strongest test to date of SDO’s role as a stable trait that influences the development of prejudice, while highlighting LGM as a valuable tool for social and political psychology

WFPC2 Observations of Compact Star Cluster Nuclei in Low Luminosity Spiral Galaxies

We have used the Wide Field Planetary Camera 2 aboard the Hubble Space Telescope to image the compact star cluster nuclei of the nearby, late-type, low-luminosity spiral galaxies NGC 4395, NGC 4242, and ESO 359-029. We also analyze archival WFPC2 observations of the compact star cluster nucleus of M33. A comparative analysis of the structural and photometric properties of these four nuclei is presented. All of the nuclei are very compact, with luminosity densities increasing at small radii to the resolution limit of our data. NGC 4395 contains a Seyfert 1 nucleus with a distinct bipolar structure and bright associated filaments which are likely due to [OIII] emission. The M33 nucleus has a complex structure, with elongated isophotes and possible signatures of weak activity, including a jet-like component. The other two nuclei are not known to be active, but share similar physical size scales and luminosities to the M33 and NGC 4395 nuclei. The circumnuclear environments of all four of our program galaxies are extremely diffuse, have only low-to-moderate star formation, and appear to be devoid of large quantities of dust. The central gravitational potentials of the galaxies are also quite shallow, making the origin of these types of `naked' nuclei problematic.Comment: to appear in the July 1999 Astronomical Journal; 38 pages (Latex), 5 tables (postscript), 21 figures (gif); postscript versions of the figures may be obtained via anonymous ftp at ftp://ftp.cv.nrao.edu/NRAO-staff/lmatthew/lanl-nucle

Echoes from Ancient Supernovae in the Large Magellanic Cloud

In principle, the light from historical supernovae could still be visible as scattered-light echoes even centuries later. However, while echoes have been discovered around some nearby extragalactic supernovae well after the explosion, targeted searches have not recovered any echoes in the regions of historical Galactic supernovae. The discovery of echoes can allow us to pinpoint the supernova event both in position and age and, most importantly, allow us to acquire spectra of the echo light to type the supernova centuries after the direct light from the explosion first reached the Earth. Here we report on the discovery of three faint new variable surface brightness complexes with high apparent proper motion pointing back to well-defined positions in the Large Magellanic Cloud (LMC). These positions correspond to three of the six smallest (and likely youngest) previously catalogued supernova remnants, and are believed to be due to thermonuclear (Type Ia) supernovae. Using the distance and proper motions of these echo arcs, we estimate ages of 610 and 410 yr for the echoes #2 and #3.Comment: 13 pages, 3 figures, 1 table. PDF format. Note: This paper has been accepted by Nature for publication as a letter. It is embargoed for discussion in the popular press until publication in Natur

Galaxy Zoo: the dependence of morphology and colour on environment

We analyse the relationships between galaxy morphology, colour, environment and stellar mass using data for over 100,000 objects from Galaxy Zoo, the largest sample of visually classified morphologies yet compiled. We conclusively show that colour and morphology fractions are very different functions of environment. Both are sensitive to stellar mass; however, at fixed stellar mass, while colour is also highly sensitive to environment, morphology displays much weaker environmental trends. Only a small part of both relations can be attributed to variation in the stellar mass function with environment. Galaxies with high stellar masses are mostly red, in all environments and irrespective of their morphology. Low stellar-mass galaxies are mostly blue in low-density environments, but mostly red in high-density environments, again irrespective of their morphology. The colour-density relation is primarily driven by variations in colour fractions at fixed morphology, in particular the fraction of spiral galaxies that have red colours, and especially at low stellar masses. We demonstrate that our red spirals primarily include galaxies with true spiral morphology. We clearly show there is an environmental dependence for colour beyond that for morphology. Before using the Galaxy Zoo morphologies to produce the above results, we first quantify a luminosity-, size- and redshift-dependent classification bias that affects this dataset, and probably most other studies of galaxy population morphology. A correction for this bias is derived and applied to produce a sample of galaxies with reliable morphological type likelihoods, on which we base our analysis.Comment: 25 pages, 20 figures (+ 6 pages, 11 figures in appendices); moderately revised following referee's comments; accepted by MNRA