Hot Dust and PAH Emission at Low Metallicity: A Spitzer Survey of Local Group and Other Nearby Dwarf Galaxies

We present Spitzer Space Telescope 4.5 and 8.0 micron imaging of 15 Local Group and nearby dwarf galaxies. Our sample spans a range of more than one dex in nebular metallicity and over three orders of magnitude in current star formation rate, allowing us to examine the dependence of the diffuse 8 micron emission, originating from hot dust and PAHs, on these parameters. We detect prominent diffuse 8 micron emission in four of the most luminous galaxies in the sample (IC 1613, IC 5152, NGC 55, and NGC 3109), low surface brightness emission from four others (DDO 216, Sextans A, Sextans B, WLM), and no diffuse emission from the remaining objects. We observe general correlations of the diffuse 8 micron emission with both the current star formation rate and the nebular metallicity of the galaxies in our sample. However, we also see exceptions to these correlations that suggest other processes may also have a significant effect on the generation of hot dust/PAH emission. These systems all have evidence for old and intermediate age star formation, thus the lack of diffuse 8 micron emission cannot be attributed to young galaxy ages. Also, we find that winds are unlikely to explain the paucity of diffuse 8 micron emission, since high resolution imaging of the neutral gas in these objects show no evidence of blowout. Additionally, we propose the lack of diffuse 8 micron emission in low-metallicity systems may be due to the destruction of dust grains by supernova shocks, assuming the timescale to regrow dust grains and PAH molecules is long compared to the destruction timescale. The most likely explanation for the observed weak diffuse 8 micron emission is at least partly due to a general absence of dust (including PAHs), in agreement with their low metallicities.Comment: Accepted by ApJ, 26 pages, 8 figures, version with high-resolution figures available at: http://webusers.astro.umn.edu/~djackson

The Interstellar Medium of Star-forming Irregular Galaxies: The View with ISO

We present mid-infrared imaging and far-infrared (FIR) spectroscopy of 5 IBm galaxies observed by ISO as part of our larger study of the inter- stellar medium of galaxies. Most of the irregulars in our sample are very actively forming stars. The mid-infrared imaging was in a band centered at 6.75 microns that is dominated by polycyclic aromatic hydrocarbons (PAHs) and in a band centered at 15 microns that is dominated by small dust grains. The spectroscopy of 3 of the galaxies includes [CII]158 microns and [OI]63 microns, important coolants of photodissociation regions (PDRs), and [OIII]88 microns and [NII]122 microns, which come from ionized gas. [OI]145 microns and [OIII]52 microns were measured in one galaxy as well. These data are combined with PDR and HII region models to deduce properties of the interstellar medium of these galaxies.Comment: To be published in ApJ, Apr 10, 2001; higher resolution figures available from ftp.lowell.edu, cd pub/dah/isopaper

The role of group membership among youths on the formation of social identity

The role of group membership in social identity formation is investigated. The study aims to answer the similarity and differences of organizational cultures and youth subcultures based on the norms, values and attitudes possessed by the group, as well as how these norms, values, and attitudes of affect the formation of the social identity of a member. To investigate the problem, four youths each from organizational culture groups and from youth subcultures groups were interviewed. Results show that organizational cultures and youth subcultures are different in terms of the quantity of the norms, values, and attitudes being imposed, and similar in terms of having a considerable effect on the social identity of the youths. This means that the types of group youths are members of have an important role in their identity building. Implying that it is critical to youths choose a group that facilitates good character building

Dust and atomic gas in dwarf irregular galaxies of the M81 group: the SINGS and THINGS view

Original article can be found at: http://www.iop.org/EJ/journal/apj Copyright American Astronomical Society. [Full text of this article is not available in the UHRA]Peer reviewe

Different Genetic Signatures of Small‐Cell Lung Cancer Characterize <scp>Anti‐GABA_BR</scp> and <scp>Anti‐Hu</scp> Paraneoplastic Neurological Syndromes

International audienceObjective: Small-cell lung cancer (SCLC) is the malignancy most frequently associated with paraneoplastic neurological syndromes (PNS) and can trigger different antibody responses against intracellular (Hu) or neuronal surface (GABA B R) antigens. Our aim was to clarify whether the genomic and transcriptomic features of SCLC are different in patients with anti-GABA B R or anti-Hu PNS compared with SCLC without PNS. Methods: A total of 76 SCLC tumor samples were collected: 34 anti-Hu, 14 anti-GABA B R, and 28 SCLC without PNS. The study consisted of 4 steps: (1) pathological confirmation; (2) next generation sequencing using a panel of 98 genes