Structural Evidence for Environment-Driven Transformation of the Blue Galaxies in Local Abell Clusters - A85, A496, and A754

We compare V-band structural properties of cluster and field galaxies, to test whether much of the current cluster membership resulted from the transformation of infalling spirals into red early types. We use 140 galaxies from 3 z<0.6 Abell clusters (A85,A496,A754 - spectroscopic membership) with blue colors, and compare them to 80 field galaxies with similar colors and luminosities. Our previous work (McIntosh et al. 2004, ApJ submitted) shows that the blue galaxies in these local clusters are a recently infalling population that has yet to encounter the dense core. We quantify galaxy internal structure from 2D B/D decompositions using GIM2D. We observe structural differences between blue galaxies in clusters, compared to the field. Most blue cluster members are physically smaller and fainter than their field counterparts. At a matched size and luminosity, recent arrivals are smoother in appearance, yet their total light is as disk-dominated as in normal field spirals. Moreover, 50% of blue cluster galaxies have blue cores or globally blue color profiles, in contrast with field spirals that have typically red color gradients. Without environment dependent evolution outside of cluster cores, we expect blue disk galaxies in clusters and the field to have similar morphologies, sizes, and color gradients. We show conclusively that galaxy properties do reflect the environment in which the galaxy is found. The data show that the transformation of accreted galaxies is not confined to the dense cluster core. The overall properties of bluer cluster galaxies are best explained by environment-driven transformation of accreted field spirals, and our results suggest that the processes that govern color and morphological evolution occur separately. (abridged)Comment: Accepted for publication in ApJ, 23 pages, Latex using emulateapj5.sty and onecolfloat.sty (included), 15 figures, version with full resolution Figs. 2 and 5 at http://www.astro.umass.edu/~dmac/Papers/transf.hires.ps Substantial revisions of Introduction and Discussion; extensive minor changes throughout paper following recommendations by referee; conclusions unchanged except for removal of pre-processing interpretatio

The accretion origin of the Milky Way's stellar halo

We have used data from the Sloan Digital Sky Survey (SDSS) Data Release 5 to explore the overall structure and substructure of the stellar halo of the Milky Way using about 4 million color-selected main sequence turn-off stars. We fit oblate and triaxial broken power-law models to the data, and found a `best-fit' oblateness of the stellar halo 0.5<c/a<0.8, and halo stellar masses between Galactocentric radii of 1 and 40kpc of (3.7+/-1.2)x10^8 M_sun. The density profile of the stellar halo is approximately r^{-3}; it is possible that the power law slope is shallower inside 20kpc and steeper outside that radius. Yet, we found that all smooth and symmetric models were very poor fits to the distribution of stellar halo stars because the data exhibit a great deal of spatial substructure. We quantified deviations from a smooth oblate/triaxial model using the RMS of the data around the model profile on scales >~100pc, after accounting for the (known) contribution of Poisson uncertainties. The fractional RMS deviation of the actual stellar distribution from any smooth, parameterized halo model is >~40%: hence, the stellar halo is highly structured. We compared the observations with simulations of galactic stellar halos formed entirely from the accretion of satellites in a cosmological context by analysing the simulations in the same way as the data. While the masses, overall profiles, and degree of substructure in the simulated stellar halos show considerable scatter, the properties and degree of substructure in the Milky Way's halo match well the properties of a `typical' stellar halo built exclusively out of the debris from disrupted satellite galaxies. Our results therefore point towards a picture in which an important fraction of the Milky Way's stellar halo has been accreted from satellite galaxies.Comment: Submitted to the Astrophysical Journal. 14 pages; 11 figure

NAPOLI-1 phase 3 study of liposomal irinotecan in metastatic pancreatic cancer: Final overall survival analysis and characteristics of long-term survivors

BACKGROUND: Liposomal irinotecan (nal-IRI) plus 5-fluorouracil and leucovorin (5-FU/LV) is approved for patients with metastatic pancreatic ductal adenocarcinoma (mPDAC) previously treated with gemcitabine-based therapy. This approval was based on significantly improved median overall survival compared with 5-FU/LV alone (6.1 vs 4.2 months; hazard ratio [HR], 0.67) in the global phase 3 NAPOLI-1 trial. Here, we report the final survival analysis and baseline characteristics associated with long-term survivors (survival of ≥1 year) in the NAPOLI-1 trial. PATIENTS AND METHODS: Patients with mPDAC were randomised to receive nal-IRI + 5-FU/LV (n = 117), nal-IRI (n = 151), or 5-FU/LV (n = 149) for the first 4 weeks of 6-week cycles. Baseline characteristics and efficacy in the overall population were compared with those in patients who survived ≥1 year. Through 16th November 2015, 382 overall survival events had occurred. RESULTS: The overall survival advantage for nal-IRI+5-FU/LV vs 5-FU/LV was maintained from the original nanoliposomal irinotecan with fluorouracil and folinic acid in metastatic pancreatic cancer after previous gemcitabine-based therapy (NAPOLI-1) analysis (6.2 vs 4.2 months, respectively; HR, 0.75; 95% confidence interval: 0.57-0.99). Median progression-free survival, objective response rate and disease control rate also favoured nal-IRI+5-FU/LV therapy. Estimated one-year overall survival rates were 26% with nal-IRI+5-FU/LV and 16% with 5-FU/LV. Baseline characteristics associated with long-term survival in the nal-IRI+5-FU/LV arm were Karnofsky performance status ≥90, age ≤65 years, lower CA19-9 levels, neutrophil-to-lymphocyte ratio ≤5 and no liver metastases. No new safety concerns were detected. CONCLUSIONS: The survival benefits of nal-IRI+5-FU/LV versus 5-FU/LV were maintained over an extended follow-up, and prognostic markers of survival ≥1 year were identified. CLINICAL TRIAL REGISTRATION NUMBER: NCT01494506

Strong Balmer lines in old stellar populations: No need for young ages in ellipticals?

Comparing models of Simple Stellar Populations (SSP) with observed line strengths generally provides a tool to break the age-metallicity degeneracy in elliptical galaxies. Due to the wide range of Balmer line strengths observed, ellipticals have been interpreted to exhibit an appreciable scatter in age. In this paper, we analyze Composite Stellar Population models with a simple mix of an old metal-rich and an old metal-poor component. We show that these models simultaneously produce strong Balmer lines and strong metallic lines without invoking a young population. The key to this result is that our models are based on SSPs that better match the steep increase of Hbeta in metal-poor globular clusters than models in the literature. Hence, the scatter of Hbeta observed in cluster and luminous field elliptical galaxies can be explained by a spread in the metallicity of old stellar populations. We check our model with respect to the so-called G-dwarf problem in ellipticals. For a galaxy subsample covering a large range in UV-V colors we demonstrate that the addition of an old metal-poor subcomponent does not invalidate other observational constraints like colors and the flux in the mid-UV.Comment: Accepted for publication in ApJ Main Journal, 9 pages, 5 figure

Warm Dust and Spatially Variable PAH Emission in the Dwarf Starburst Galaxy NGC 1705

We present Spitzer observations of the dwarf starburst galaxy NGC 1705 obtained as part of SINGS. The galaxy morphology is very different shortward and longward of ~5 microns: short-wavelength imaging shows an underlying red stellar population, with the central super star cluster (SSC) dominating the luminosity; longer-wavelength data reveals warm dust emission arising from two off-nuclear regions offset by ~250 pc from the SSC. These regions show little extinction at optical wavelengths. The galaxy has a relatively low global dust mass (~2E5 solar masses, implying a global dust-to-gas mass ratio ~2--4 times lower than the Milky Way average). The off-nuclear dust emission appears to be powered by photons from the same stellar population responsible for the excitation of the observed H Alpha emission; these photons are unassociated with the SSC (though a contribution from embedded sources to the IR luminosity of the off-nuclear regions cannot be ruled out). Low-resolution IRS spectroscopy shows moderate-strength PAH emission in the 11.3 micron band in the eastern peak; no PAH emission is detected in the SSC or the western dust emission complex. There is significant diffuse 8 micron emission after scaling and subtracting shorter wavelength data; the spatially variable PAH emission strengths revealed by the IRS data suggest caution in the interpretation of diffuse 8 micron emission as arising from PAH carriers alone. The metallicity of NGC 1705 falls at the transition level of 35% solar found by Engelbracht and collaborators; the fact that a system at this metallicity shows spatially variable PAH emission demonstrates the complexity of interpreting diffuse 8 micron emission. A radio continuum non-detection, NGC 1705 deviates significantly from the canonical far-IR vs. radio correlation. (Abridged)Comment: ApJ, in press; please retrieve full-resolution version from http://www.astro.wesleyan.edu/~cannon/pubs.htm

The Nature of Infrared Emission in the Local Group Dwarf Galaxy NGC 6822 As Revealed by Spitzer

We present Spitzer imaging of the metal-deficient (Z ~30% Z_sun) Local Group dwarf galaxy NGC 6822. On spatial scales of ~130 pc, we study the nature of IR, H alpha, HI, and radio continuum emission. Nebular emission strength correlates with IR surface brightness; however, roughly half of the IR emission is associated with diffuse regions not luminous at H alpha (as found in previous studies). The global ratio of dust to HI gas in the ISM, while uncertain at the factor of ~2 level, is ~25 times lower than the global values derived for spiral galaxies using similar modeling techniques; localized ratios of dust to HI gas are about a factor of five higher than the global value in NGC 6822. There are strong variations (factors of ~10) in the relative ratios of H alpha and IR flux throughout the central disk; the low dust content of NGC 6822 is likely responsible for the different H alpha/IR ratios compared to those found in more metal-rich environments. The H alpha and IR emission is associated with high-column density (> ~1E21 cm^-2) neutral gas. Increases in IR surface brightness appear to be affected by both increased radiation field strength and increased local gas density. Individual regions and the galaxy as a whole fall within the observed scatter of recent high-resolution studies of the radio-far IR correlation in nearby spiral galaxies; this is likely the result of depleted radio and far-IR emission strengths in the ISM of this dwarf galaxy.Comment: ApJ, in press; please retrieve full-resolution version from http://www.astro.wesleyan.edu/~cannon/pubs.htm

CD1a autoreactive T cells recognize natural skin oils that function as headless antigens

CD1a autoreactive T cells are common in human blood and skin, but the search for natural autoantigens has been confounded by background T cell responses to CD1 proteins and self lipids. After capturing CD1a-lipid complexes, we gently eluted ligands, while preserving unliganded CD1a for testing lipids from tissues. CD1a released hundreds of ligands of two types. Inhibitory ligands were ubiquitous membrane lipids with polar headgroups, whereas stimulatory compounds were apolar oils. CD1a autoantigens naturally accumulate in epidermis and sebum, where they were identified as squalene and skin waxes. T cell activation by skin oils suggests that headless mini-antigens nest within CD1a and displace non-antigenic resident lipids with large head groups. Oily autoantigens naturally coat the skin's surface, pointing to a new mechanism of barrier immunity

6-thioguanine treatment in inflammatory bowel disease: A critical appraisal by a European 6-TG working party

Recently, the suggestion to use 6-thioguanine (6-TG) as an alternative thiopurine in patients with inflammatory bowel disease (IBD) has been discarded due to reports about possible (hepato) toxicity. During meetings arranged in Vienna and Prague in 2004, European experts applying 6-TG further on in IBD patients presented data on safety and efficacy of 6-TG. After thorough evaluation of its risk-benefit ratio, the group consented that 6-TG may still be considered as a rescue drug in stringently defined indications in IBD, albeit restricted to a clinical research setting. As a potential indication for administering 6-TG, we delineated the requirement for maintenance therapy as well as intolerance and/or resistance to aminosalicylates, azathioprine, 6-mercaptopurine, methotrexate and infliximab. Furthermore, indications are preferred in which surgery is thought to be inappropriate. The standard 6-TG dosage should not exceed 25 mg daily. Routine laboratory controls are mandatory in short intervals. Liver biopsies should be performed after 6-12 months, three years and then three-yearly accompanied by gastroduodenoscopy, to monitor for potential hepatotoxicity, including nodular regenerative hyperplasia (NRH) and veno-occlusive disease (VOD). Treatment with 6-TG must be discontinued in case of overt or histologically proven hepatotoxicity. Copyright (c) 2006 S. Karger AG, Basel

Data Deluge in Astrophysics: Photometric Redshifts as a Template Use Case

Astronomy has entered the big data era and Machine Learning based methods have found widespread use in a large variety of astronomical applications. This is demonstrated by the recent huge increase in the number of publications making use of this new approach. The usage of machine learning methods, however is still far from trivial and many problems still need to be solved. Using the evaluation of photometric redshifts as a case study, we outline the main problems and some ongoing efforts to solve them.Comment: 13 pages, 3 figures, Springer's Communications in Computer and Information Science (CCIS), Vol. 82

Applications of patching to quadratic forms and central simple algebras

This paper provides applications of patching to quadratic forms and central simple algebras over function fields of curves over henselian valued fields. In particular, we use a patching approach to reprove and generalize a recent result of Parimala and Suresh on the u-invariant of p-adic function fields, for p odd. The strategy relies on a local-global principle for homogeneous spaces for rational algebraic groups, combined with local computations.Comment: 48 pages; connectivity now required in the definition of rational group; beginning of Section 4 reorganized; other minor change