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2013-05-30T14:00
Nearby Galaxies
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1400 |
Venn, Kim |
Galactic Archaeology |
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The Milky Way Galaxy is recognized as being a complex ensemble of stellar populations, each having a characteristic age, metallicity distribution function, and dynamical properties. Many large-scale and international projects are being carried out to study the details of these stellar populations, to improve our understanding of the galaxy formation steps from the accretion of primordial subhalos and HI infall to the disk(s), halo(s), and bulge that we see today. Both low resolution (radial velocities and metallicities) and high resolution (element abundance ratios) spectroscopy are needed to disentangle the various stellar populations, to separate the thin and thick disks to consider their origins, and to identify unique features such as recently accreted dwarf galaxies. Low and high resolution spectroscopic surveys are also used to search for the most metal-poor stars which are presumed to be old and thereby associated with the earliest epochs of the formation of the Galaxy. Optical and IR spectroscopic surveys are needed to examine the properties of the bulge which suffers from crowding and variable extinction. In this talk, I will summarize the current state of Galactic Archaeology and discuss the impact a future ngCFHT could have on this field. |
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1415 |
Cooper, Brendan * |
The Magnetic Field at the Disk-Halo Boundary in the Milky Way |
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Magnetic fields play a central role in the structure and dynamics of galaxies. Determining the structure of the magnetic field can provide critical constraints to models attempting to explain the origin and evolution of galactic magnetism. Typically observations are either confined to the disk or to the halo of a galaxy, but very little work has been targeted at the transition between the two. Using new observations from the Dominion Radio Astrophysical Observatory synthesis array, I am endeavouring to explore this transition within our own Galaxy. In my talk, I will present my new observations and the work I have been doing to interpret them in the context of understanding how the Galactic magnetic field transitions between the disk and the halo. |
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1430 |
Lee-Waddell, Karen * |
A multi-wavelength investigation of the interacting galaxy group NGC 871/7 |
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We present Arecibo Legacy Fast ALFA (ALFALFA) maps, follow-up GMRT observations and deep CFHT optical images of the HI-rich group NGC 871/7 that harbours an intriguing HI feature, AGC 749170, with an HI mass of 10^9.5 M_sol and no obvious optical counterpart. If primordial in nature, AGC 749170 could be an extremely rare massive “dark galaxy”. Preliminary analysis of the GMRT data shows a slight extension from the feature that is directed towards the centre of the group, which may suggest a tidal origin; however, the lack of stellar components in the CFHT images (down to a limit of ~27 mag/arcsec^2) is unusual for tidal shreds of comparable HI mass. Our observations are part of a comprehensive, multi-wavelength examination of the nature and properties of the low-mass galaxy populations in three gas-rich groups in the ALFALFA survey. Each group gives evidence for both first- and second-generation dwarfs. The properties of these low-mass objects offer crucial information about the underlying structure of their environments and can give insight into their evolutionary histories. |
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1445 |
Foyle, Kelly |
Dissecting the Dust - Compact Regions in the Far-Infrared Maps of M83 |
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We investigate star formation and dust heating in the compact sources detected in the Herschel maps of M83, a nearby spiral galaxy. We use the source extraction code GETSOURCES to detect and extract sources in the far-infrared, as well as their photometry in the mid-infrared and Hα. By performing infrared SED fitting and applying an Hα based star formation rate (SFR) calibration, we derive the dust masses and temperatures, SFRs, gas masses and star formation efficiencies (SFEs). The detected sources lie exclusively on the spiral arms and represent giant molecular associations (GMAs), with gas masses and sizes of 10^6-10^8M⊙ and 200-300 pc, respectively. We find an anti-correlation between the SFEs and gas masses, consistent with a scenario where more massive GMAs are less efficient in forming stars. Dust heating is mainly due to local star formation. However, although the sources are not optically thick, the total intrinsic young stellar population luminosity can almost completely account for the dust luminosity. This suggests that other radiation sources contribute to the dust heating as well and approximately compensate for the unabsorbed fraction of UV light. |
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1500 |
Ferrarese, Laura |
Galaxy Scaling Relation and Luminosity Function from the Next Generation Virgo Cluster Survey |
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The Next Generation Virgo Cluster Survey, a ~900 hour CFHT/MegaCam Large Programme, allows us to probe the galaxy population in the Virgo cluster to a depth that, to-date, has only been attained in the Local Group. I will present a detailed investigation of the scaling relations for Virgo cluster galaxies spanning a factor of 5 million in luminosity, and the most robust determination yet of the faint end of the galaxy luminosity function. |
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1515 |
Taylor, James |
Fainter Dwarfs, Closer By |
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The abundance of dwarf satellites remains a critical test of CDM structure formation. Until recently, observational information about these scales has been limited to the Local Group. We have searched for faint analogues of Local Group dwarfs around nearby bright galaxies in SDSS DR8. By using nearby primaries, we are able to detect dwarfs four magnitudes fainter than most other recent studies. We find 4.6 ± 0.5 faint satellites per central galaxy, comparable to the abundance around the Milky Way and M31 to similar magnitudes. This measurement provides a bound on the average satellite luminosity function down to the faintest "classical" dwarfs of the Local Group, M_V ~ -8. |
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