83,607 research outputs found
The infant Milky Way
We investigate the physical properties of the progenitors of today living
Milky Way-like galaxies that are visible as Damped Lya Absorption systems and
Lya Emitters at higher redshifts (z ~ 2.3,5.7). To this aim we use a
statistical merger-tree approach that follows the formation of the Galaxy and
its dwarf satellites in a cosmological context, tracing the chemical evolution
and stellar population history of the progenitor halos. The model accounts for
the properties of the most metal-poor stars and local dwarf galaxies, providing
insights on the early cosmic star-formation. Fruitful links between Galactic
Archaeology and more distant galaxies are presented.Comment: 6 pages, 6 figures; to appear in the proceedings of the Subaru
conference on Galactic Archaeology, Shuzenji, Japan (Nov. 1-4 2011);
Astronomical Society of the Pacific Conference Series 201
The Milky Way disk
This review summarises the invited presentation I gave on the Milky Way disc.
The idea underneath was to touch those topics that can be considered hot
nowadays in the Galactic disk research: the reality of the thick disk, the
spiral structure of the Milky Way, and the properties of the outer Galactic
disk. A lot of work has been done in recent years on these topics, but a
coherent and clear picture is still missing. Detailed studies with high quality
spectroscopic data seem to support a dual Galactic disk, with a clear
separation into a thin and a thick component. Much confusion and very
discrepant ideas still exist concerning the spiral structure of the Milky Way.
Our location in the disk makes it impossible to observe it, and we can only
infer it. This process of inference is still far from being mature, and depends
a lot on the selected tracers, the adopted models and their limitations, which
in many cases are neither properly accounted for, nor pondered enough. Finally,
there are very different opinions on the size (scale length, truncation radius)
of the Galactic disk, and on the interpretation of the observed outer disk
stellar populations in terms either of external entities (Monoceros,
Triangulus-Andromeda, Canis Major), or as manifestations of genuine disk
properties (e.g., warp and flare).Comment: 7 pages, 9 figures. Full text in English. To be published in the 57
Bulletin of the Argentinian Association of Astronomy (BAAA 57
Weighing the Milky Way
We describe an experiment to measure the mass of the Milky Way galaxy. The
experiment is based on calculated light travel times along orthogonal
directions in the Schwarzschild metric of the Galactic center. We show that the
difference is proportional to the Galactic mass. We apply the result to light
travel times in a 10cm Michelson type interferometer located on Earth. The mass
of the Galactic center is shown to contribute 10^-6 to the flat space component
of the metric. An experiment is proposed to measure the effect.Comment: 10 pages, 1 figur
VISTA Milky Way public survey
We propose a public IR variability survey, named \Vista Variables in the VÃa Láctea" (V V V ), of the Milky Way bulge and an adjacent section of the mid-plane where star formation activity is high. This would take 1920 hours, covering ~ 109 point sources within an area of 520 sq deg, including 33 known globular clusters and ~ 350 open clusters. The final products will be a deep IR atlas in 5 passbands and a catalogue of ~ 106 variable point sources. These will produce a 3-D map of the surveyed region (unlike single-epoch surveys that only give 2-D maps) using well-understood primary distance indicators such as RR Lyrae stars. It will yield important information on the ages of the populations. The observations will be combined with data from MACHO, OGLE, EROS, VST, SPITZER, HST, CHANDRA, INTEGRAL, and ALMA for a complete understanding of the variable sources in the inner Milky Way. Several important implications for the history of the Milky Way, for globular cluster evolution, for the population census of the bulge and center, and for pulsation theory would follow from this survey
Living in the Milky Way
It’s finally here. Today, June 20 at 6:34 p.m., is the the summer solstice, also known as the first day of summer and, confusingly enough, midsummer’s eve. From a scientific perspective, it marks the moment the sun reaches its northernmost point in our sky. As a result of that position, it’s the shortest night and longest day if you live north of the equator. [excerpt
Chemodynamical modelling of the Milky Way
Chemodynamical models of our Galaxy that have analytic Extended Distribution
Functions (EDFs) are likely to play a key role in extracting science from
surveys in the era of Gaia.Comment: 6 pages to appear in "Reconstructing the Milky Way history:
spectroscopic surveys, asteroseismology and chemodynamical models", eds C
Chiappini, J Montalban & M Steffe
Dense Gas in the Milky Way
We present a study of dense gas emission in the Milky Way in order to serve
as a basis for comparison with extragalactic results. This study combines new
observations of HCN, CS, and CO in individual GMCs and in the Milky Way plane
with published studies of emission from these molecules in the inner 500 pc of
the Milky Way. We find a strong trend in the fraction of emission from dense
gas tracers as a function of location in the Milky Way: in the bulge,
I_{HCN}/I_{CO} = 0.081 \pm 0.004, in the plane, I_{HCN}/I_{CO} = 0.026 \pm
0.008 on average, and over the full extent of nearby GMCs, I_{HCN}/I_{CO} =
0.014 \pm 0.020. Similar trends are seen in I_{CS}/I_{CO}. The low intensities
of the HCN and CS emission in the plane suggests that these lines are produced
by gas at moderate densities; they are thus not like the emission produced by
the dense, pc-scale star forming cores in nearby GMCs. The contrast between the
bulge and disk ratios in the Milky Way is likely to be caused by a combination
of higher kinetic temperatures as well as a higher dense gas fraction in the
bulge of the Milky Way.Comment: 34 pages LaTeX, AASTEX macros, includes 11 postscript figures. To
appear in ApJ 478, March 199
Windows in the Milky Way
The objectives were twofold: (1) to study the IRAS emission levels in the vicinity of Baade's Window and in other optically transparent regions near the Galactic Center; and (2) to study the IRAS emission levels along sightlines in the Milky Way that exhibit very little CO emission. Tests were attempted to see whether the optically transparent 'windows' near the Galactic center can be identified (as FIR-weak regions) in the IRAS data base; and if so, whether the CO weak regions found elsewhere in the Milky Way represent similarly FIR weak and thus optically transparent sightlines through the Galaxy. The CO weak regions were also targeted in an effort to study the diffuse intercloud dust and its warming by the interstellar radiation field
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