6 research outputs found
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 SmallâCell Lung Cancer Characterize <scp>AntiâGABA<sub>B</sub>R</scp> and <scp>AntiâHu</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