1,525 research outputs found
Everyman\u27s Climb
Hal and Verity represent two different philosophies of learning, one used by most of us. In today’s world, authentic teaching is indeed a heroic act, but may not be the most popular. This piece draws distinctions between these choices, each time we teach a course, each day we walk into the classroom, and even when working with an individual student; they are ever present
Galaxy pairs in the SDSS - XIII. The connection between enhanced star formation and molecular gas properties in galaxy mergers.
This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society © 2018 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.We investigate the connection between star formation and molecular gas properties in galaxy mergers at low redshift (z ≤ 0.06). The study we present is based on IRAM 30-m CO(1-0) observations of 11 galaxies with a close companion selected from the Sloan Digital Sky Survey (SDSS). The pairs have mass ratios ≤4, projected separations r p ≤ 30 kpc and velocity separations ΔV ≤ 300 km s -1, and have been selected to exhibit enhanced specific star formation rates (sSFRs). We calculate molecular gas (H 2) masses, assigning to each galaxy a physically motivated conversion factor αCO, and we derive molecular gas fractions and depletion times. We compare these quantities with those of isolated galaxies from the extended CO Legacy Data base for the GALEX Arecibo SDSS Survey sample (xCOLDGASS; Saintonge et al.) with gas quantities computed in an identical way. Ours is the first study which directly compares the gas properties of galaxy pairs and those of a control sample of normal galaxies with rigorous control procedures and for which SFR and H 2 masses have been estimated using the same method. We find that the galaxy pairs have shorter depletion times and an average molecular gas fraction enhancement of 0.4 dex compared to the mass matched control sample drawn from xCOLDGASS. However, the gas masses (and fractions) in galaxy pairs and their depletion times are consistent with those of non-mergers whose SFRs are similarly elevated. We conclude that both external interactions and internal processes may lead to molecular gas enhancement and decreased depletion times.Peer reviewe
Analysis of Cellular Signaling Events by Flow Cytometry
12 pagesAll the cells are engaged on a cell communication by sending and receiving signals. Cells having the correct receptors on their surfaces will encode the plasma membrane signal recognition to intracellular signals corresponding to cellular signaling events. This process corresponds to a huge intracellular network of protein-protein or lipid-protein interactions. To avoid to be lost in this kind of maze, some general signaling pathways are most of the time present in many cell systems such as MAP kinases or PI-3 kinases pathways. These signaling pathways induce some protein phosphorylation events that can be identified by specific antibodies directed against these phosphosites (anti-phospho antibodies). Thus, these crossroads can be determined by using antibodies. A widely used method to identify these signaling events is the Western blotting or protein immunoblotting from cell extracts. However, several research groups are now developing new analytical techniques based also on the use of anti-phospho antibodies, but allowing them to detect signaling events at the single cell level. These experimental approaches are using the principles of the flow cytometry (FCM). Phosphoflow technology will provide rapid, quantitative and also multi-parameter analyses on single cells
The shortwave infrared bands response to stomatal conductance in Conference" Pear Trees (Pyrus communis L.)"
Published: 8 October 201
Progress toward sonifying Napoleon’s march and fluid flow simulations through binaural horizons
Cross-modal data analytics—that can be rendered for experience
through vision, hearing, and touch—poses a fundamental
challenge to designers. Non-linguistic sonification is a
well-researched means for non-visual pattern recognition but
higher density datasets pose a challenge. Because human hearing
is optimized for detecting locations on a horizontal plane, our
approach recruits this optimization by employing an immersive
binaural horizontal plane using auditory icons. Two case studies
demonstrate our approach: A sonic translation of a map and a
sonic translation of a computational fluid dynamics simulation
Limits on dust emission from z~5 LBGs and their local environments
We present 1.2mm MAMBO-2 observations of a field which is over-dense in Lyman
Break Galaxies (LBGs) at z~5. The field includes seven
spectroscopically-confirmed LBGs contained within a narrow (z=4.95+/-0.08)
redshift range and an eighth at z=5.2. We do not detect any individual source
to a limit of 1.6 mJy/beam (2*rms). When stacking the flux from the positions
of all eight galaxies, we obtain a limit to the average 1.2 mm flux of these
sources of 0.6mJy/beam. This limit is consistent with FIR imaging in other
fields which are over-dense in UV-bright galaxies at z~5. Independently and
combined, these limits constrain the FIR luminosity (8-1000 micron) to a
typical z~5 LBG of LFIR<~3x10^11 Lsun, implying a dust mass of Mdust<~10^8 Msun
(both assuming a grey body at 30K). This LFIR limit is an order of magnitude
fainter than the LFIR of lower redshift sub-mm sources (z~1-3). We see no
emission from any other sources within the field at the above level. While this
is not unexpected given millimetre source counts, the clustered LBGs trace
significantly over-dense large scale structure in the field at z = 4.95. The
lack of any such detection in either this or the previous work, implies that
massive, obscured star-forming galaxies may not always trace the same
structures as over-densities of LBGs, at least on the length scale probed here.
We briefly discuss the implications of these results for future observations
with ALMA.Comment: 10 pages, 6 figures, MNRAS Accepte
A new perspective on the submillimetre galaxy MM 18423+5938 at redshift 3.9296 from radio continuum imaging
The bright submillimetre (sub-mm) galaxy MM 18423+5938 at redshift 3.9296 has
been predicted from mid-infrared and millimetre photometry to have an
exceptionally large total infrared (IR) luminosity. We present new radio
imaging at 1.4 GHz with the Westerbork Synthesis Radio Telescope that is used
to determine a radio-derived total IR luminosity for MM 18423+5938 via the well
established radio-far-infrared correlation. The flux density is found to be
S_1.4 GHz = 217 +/- 37 \mu Jy, which corresponds to a rest-frame luminosity
density of L_1.4 GHz = 2.32 +/- 0.40 x 10^25 / u W / Hz, where u is the
magnification from a probable gravitational lens. The radio-derived total IR
luminosity and star-formation rate are L_8-1000 \mu m = 5.6^+4.1_-2.4 x 10^13 /
u L_sol and SFR = 9.4^+7.4_-4.9 x 10^3 / u M_sol / yr, respectively, which are
~9 times smaller than those previously reported. These differences are
attributed to the IR spectral energy distribution of MM 18423+5938 being poorly
constrained by the limited number of reliable photometric data that are
currently available, and from a previous misidentification of the object at 70
\mu m. Using the radio derived total IR luminosity as a constraint, the
temperature of the cold dust component is found to be T ~ 24^+7_-5 K for a dust
emissivity of \beta = 1.5 +/- 0.5. The radio-derived properties of this galaxy
are still large given the low excitation temperature implied by the CO emission
lines and the temperature of the cold dust. Therefore, we conclude that MM
18423+5938 is probably gravitationally lensed.Comment: 5 pages, 2 figures, 1 table, accepted for publication in MNRAS
Letter
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