0311058 (2004PASP..116..345C)
ANNz: estimating photometric redshifts using artificial neural networks
Collister, Lahav
Use Artificial Neural Networks as a software package for photometric redshift estimation. Input to ANNz: photometry and redshift from a training set of galaxies---when input is large, ANNz is highly competitive compared with traditional template-fitting methods. Demonstrated on SDSS DR1; for 0<z<0.7, sigma_rms = 0.023 (whoa--only bright samples?). Non-ideal conditions simulated and its impact on photo-z accuracy assessed.
Estimating photometric redshifts with artificial neural networks
Firth, Lahav, Somerville
Investigate ANNs method of estimating redshifts. If a large spectro-z training set is available, then photo-z accuracy is equally good or better than template based method. Bayesian priors taken into account, where the prior is "the underlying redshift distribution". Inputs other than galaxy colors (e.g., morphology, angular size, surface brightness) is easily incorporated.
* check out PHAT paper before we believe in the wonders of ANNs.
* As for the "other inputs", you can also add ellipticity (to capture edge-on spirals which can be dusty) and the apparent magnitude (faraway objects are dimmer).
1106.6089
How neutral is the intergalactic medium surrounding the redshift z=7.085 quasar ULAS J1120+0641?
JS Bolton, et al
* check out day 33 for related papers.
* damped Lya system: gaseous objects in the universe detected in the spectra of quasars, with column density larger than 1e20 atoms/cm^2 (they're high). Caused by HI Lyman alpha lines broadened by radiation damping. Thought to be related to gas rich galaxies at all redshifts that they are observed.
This particular quasar at z=7.0 has a highly ionized zone which is smaller than similar quasars at z=6. Simulations show transmission profile consistent with IGM with f_HI>0.1, and that this quasar has been bright for 1e6 to 1e7 years. Observed spectrum consistent with IGM neutral fractions of f_HI~1e-3 to 1e-4, which is low--only a 5% probability of simulated sight-lines. Theoretically challenging to accept that 1e9 M_sun mass SMBH (which is what is inferred in 1106.6088) could grow at this redshift, unless it had grown during a previous optically obscured phase.
1106.6054
The declining importance of major mergers for galaxy assembly at 1<z<2
Williams, Quadri, Franx
Investigate the incidence of close galaxy pairs between z=0.4-2.0; this is connected to the merger rate. Distinguish "dry mergers" (two red galaxies) with those that include SF constituents. About 4-7% of red, 1e10.5 M_sun galaxies have similar-mass galaxy w/in 30 Mpc/h; with minor companion included (down to 1:10 mass ratio), "dry" pair fraction increases to 5-15%. Pair fraction is constant to z=2; implies most mergers occur at z<1.
1106.6090
A Monster in the early universe
Willott
The most distant quasar yet discovered--sets constraints on the formation mechanism of BHs. Can see neutral hydrogen in IGM.
1107.1033
Cosmographic Degeneracy
Shafieloo, Linder
Examine DE and matter densities allowed by precision distance measurements, in the presence of spatial curvature and (nearly) arbitrary DE equation of state. The degeneracy is huge, when only Luminosity distance is used. Need other stuff to break degeneracy, e.g., H_0, growth of structure, etc.
* could have shown how the degeneracy is broken with the other measurements.
1107.1075
The case for testing MOND using LISA pathfinder
Magueijo, Mozaffari
Quantify potential for testing MOND with LISA, if a saddle point flyby is incorporated into the mission. The SNR is large (x10 ~ x100), even after accounting for known systematics (self-gravity, Newtonian BG). Only the Einstein-Aether formulation would survive a negative result.
* this abstract doesn't say what kind of results are expected from LISA. or maybe I just didn't understand.
1107.1157
W-band prototype of platelet feed-horn array for CMB polarization measurements
Del Torto et al
Design and performance of a 2x2 prototype array of corrugated feed-horns in W-band. Important for CMB polarization measurements.
* corrugated feed horns: horn with parallel slots or grooves, small compared with a wavelength, convering the inside surface of the horn, transverse to the axis. They have wider bandwidth and smaller sidelobes and cross-polarization.
1107.1209
PTF1 J071912.13+485834.0: An outbursting AM CVn system discovered by a synoptic survey
Levitan, ... Bloom, ... Nugent, Poznanski, ... etal
* AM CVn star: a cataclysmic variable star, where the donor star lacks Hydrogen (usually a Helium star). A white dwarf accretes hydrogen-poor matter from a compact companion stars. They have extremely short orbital periods (5 to 65 minutes). Predicted to be a strong source for LISA. The donor can be: white dwarf, helium star, or evolved main sequence star.
* Cataclysmic variable star: stars which irregularly increase in brightness by a large factor, then drop back down to a quiescent state (initially called 'novae'). Consists of a white dwarf primary with an accretion disc, and a donor star. The infalling matter rich in Hydrogen form an accretion disk, and strong UV and X-ray emission seen from this disc. Outbursts occur when the density and temperature at the bottom of the accumulated hydrogen layer rise high enough to ignite nuclear fusion reactions. Usually quite blue.
* dwarf novae: current theory suggests that these novae are caused by instability in the accretion disc, which collapse onto the white dwarf.
Detected AM CVn system at the Palomar Transit Factory. This one has a period of 26.77 pm 0.02 minutes. Found a super-outburst of 65 day duration, along with "normal" outbursts. Compare with other AM CVn systems. Use quiescent phase spectroscopy to determine the origin of the photometric variability (what is it??!). Compare with SU UMa-type (dwarf novae) CV. PTF may more than double the number the outbursting AM CVn systems known.
1107.1211
Isocurvature models and BAO II: gains from combining CMB and LSS
Carbone, Mangilli, Verde
If there are isocurvature contributions in the primordial perturbations, then even if its tiny, it would affect standard ruler calibration from CMB to BAO interpretation, and introduce bias in the dark energy properties that are larger than forecasted statistical errors (!). This work: adopt fiducial cosmology which includes varying w and curvature; include galaxy power spectra along with BAO, and consider a joint analysis of Planck-like CMB experiment and spaced-based LSS probe similar to proposed surveys. Incorrect assumption on the isocurvature fraction become negligible wrt statistical errors once the LSS information is included.
* an important point, if you don't want to put a prior such as isocurvature=0 and curvature=0.
1109.3182
Pricision cosmology wit ha wide are XMM cluster survey
Pierre, et al
XMM-type x-ray cluster survey covering 50-200 deg^2---get cluster counts, and 2-pt cluster correlation function. Model shot noise and sample variance, as well as survey window functions. Constraints on the equation of state of the DE for various survey configurations. Investigate impact of cluster mass measurements, correlation function, and of the 1<z<2 cluster population. With 20Ms observation time, it is possible constrain DE at a level comparable to other next-generation cosmic probes. Survey can also provide insights into physics of high-z clusters and AGN properties.
1104.1800
Inflationary tensor fluctuations, as viewed by Ashtekar variables and their imaginary friends
Bethke, Magueijo
* whoa, i'm going to read this in my imagination.
* Ashtekar variables: represent an unusual way to rewrite the metric on the 3-d spatial slices in terms of a SU(2) gauge field. They are the key building block of loop quantum gravity.
* Loop quantum gravity: A non-perturbative theory of quantum gravity. "Loop gravity" or "quantum geometry". a proposed quantum theory of spacetime which attempts to reconcile the theories of quantum mechanics and general relativity. It suggests that space can be viewed as an extremely ifne fabric or network "woven" of finite quantized loops of excited gravitational fields called spin networks; viewed over time, they are called spin foam (different from quantum foam). A manor quantum gravity contender with string theory. Loop quantum gravity does not require higher dimensions.
* Immirzi parameter: A numerical coefficient appearing in loop quantum gravity.
Negative energy non-physical, left with usual graviton modes, but with a chiral asymmetry in the vacuum energy and fluctuations.
* There is no way I understood what went on in this abstract.
1106.6089
How neutral is the intergalactic medium surrounding the redshift z=7.085 quasar ULAS J1120+0641?
JS Bolton, et al
* check out day 33 for related papers.
* damped Lya system: gaseous objects in the universe detected in the spectra of quasars, with column density larger than 1e20 atoms/cm^2 (they're high). Caused by HI Lyman alpha lines broadened by radiation damping. Thought to be related to gas rich galaxies at all redshifts that they are observed.
This particular quasar at z=7.0 has a highly ionized zone which is smaller than similar quasars at z=6. Simulations show transmission profile consistent with IGM with f_HI>0.1, and that this quasar has been bright for 1e6 to 1e7 years. Observed spectrum consistent with IGM neutral fractions of f_HI~1e-3 to 1e-4, which is low--only a 5% probability of simulated sight-lines. Theoretically challenging to accept that 1e9 M_sun mass SMBH (which is what is inferred in 1106.6088) could grow at this redshift, unless it had grown during a previous optically obscured phase.
1106.6054
The declining importance of major mergers for galaxy assembly at 1<z<2
Williams, Quadri, Franx
Investigate the incidence of close galaxy pairs between z=0.4-2.0; this is connected to the merger rate. Distinguish "dry mergers" (two red galaxies) with those that include SF constituents. About 4-7% of red, 1e10.5 M_sun galaxies have similar-mass galaxy w/in 30 Mpc/h; with minor companion included (down to 1:10 mass ratio), "dry" pair fraction increases to 5-15%. Pair fraction is constant to z=2; implies most mergers occur at z<1.
1106.6090
A Monster in the early universe
Willott
The most distant quasar yet discovered--sets constraints on the formation mechanism of BHs. Can see neutral hydrogen in IGM.
1107.1033
Cosmographic Degeneracy
Shafieloo, Linder
Examine DE and matter densities allowed by precision distance measurements, in the presence of spatial curvature and (nearly) arbitrary DE equation of state. The degeneracy is huge, when only Luminosity distance is used. Need other stuff to break degeneracy, e.g., H_0, growth of structure, etc.
* could have shown how the degeneracy is broken with the other measurements.
1107.1075
The case for testing MOND using LISA pathfinder
Magueijo, Mozaffari
Quantify potential for testing MOND with LISA, if a saddle point flyby is incorporated into the mission. The SNR is large (x10 ~ x100), even after accounting for known systematics (self-gravity, Newtonian BG). Only the Einstein-Aether formulation would survive a negative result.
* this abstract doesn't say what kind of results are expected from LISA. or maybe I just didn't understand.
1107.1157
W-band prototype of platelet feed-horn array for CMB polarization measurements
Del Torto et al
Design and performance of a 2x2 prototype array of corrugated feed-horns in W-band. Important for CMB polarization measurements.
* corrugated feed horns: horn with parallel slots or grooves, small compared with a wavelength, convering the inside surface of the horn, transverse to the axis. They have wider bandwidth and smaller sidelobes and cross-polarization.
1107.1209
PTF1 J071912.13+485834.0: An outbursting AM CVn system discovered by a synoptic survey
Levitan, ... Bloom, ... Nugent, Poznanski, ... etal
* AM CVn star: a cataclysmic variable star, where the donor star lacks Hydrogen (usually a Helium star). A white dwarf accretes hydrogen-poor matter from a compact companion stars. They have extremely short orbital periods (5 to 65 minutes). Predicted to be a strong source for LISA. The donor can be: white dwarf, helium star, or evolved main sequence star.
* Cataclysmic variable star: stars which irregularly increase in brightness by a large factor, then drop back down to a quiescent state (initially called 'novae'). Consists of a white dwarf primary with an accretion disc, and a donor star. The infalling matter rich in Hydrogen form an accretion disk, and strong UV and X-ray emission seen from this disc. Outbursts occur when the density and temperature at the bottom of the accumulated hydrogen layer rise high enough to ignite nuclear fusion reactions. Usually quite blue.
* dwarf novae: current theory suggests that these novae are caused by instability in the accretion disc, which collapse onto the white dwarf.
Detected AM CVn system at the Palomar Transit Factory. This one has a period of 26.77 pm 0.02 minutes. Found a super-outburst of 65 day duration, along with "normal" outbursts. Compare with other AM CVn systems. Use quiescent phase spectroscopy to determine the origin of the photometric variability (what is it??!). Compare with SU UMa-type (dwarf novae) CV. PTF may more than double the number the outbursting AM CVn systems known.
1107.1211
Isocurvature models and BAO II: gains from combining CMB and LSS
Carbone, Mangilli, Verde
If there are isocurvature contributions in the primordial perturbations, then even if its tiny, it would affect standard ruler calibration from CMB to BAO interpretation, and introduce bias in the dark energy properties that are larger than forecasted statistical errors (!). This work: adopt fiducial cosmology which includes varying w and curvature; include galaxy power spectra along with BAO, and consider a joint analysis of Planck-like CMB experiment and spaced-based LSS probe similar to proposed surveys. Incorrect assumption on the isocurvature fraction become negligible wrt statistical errors once the LSS information is included.
* an important point, if you don't want to put a prior such as isocurvature=0 and curvature=0.
1109.3182
Pricision cosmology wit ha wide are XMM cluster survey
Pierre, et al
XMM-type x-ray cluster survey covering 50-200 deg^2---get cluster counts, and 2-pt cluster correlation function. Model shot noise and sample variance, as well as survey window functions. Constraints on the equation of state of the DE for various survey configurations. Investigate impact of cluster mass measurements, correlation function, and of the 1<z<2 cluster population. With 20Ms observation time, it is possible constrain DE at a level comparable to other next-generation cosmic probes. Survey can also provide insights into physics of high-z clusters and AGN properties.
1104.1800
Inflationary tensor fluctuations, as viewed by Ashtekar variables and their imaginary friends
Bethke, Magueijo
* whoa, i'm going to read this in my imagination.
* Ashtekar variables: represent an unusual way to rewrite the metric on the 3-d spatial slices in terms of a SU(2) gauge field. They are the key building block of loop quantum gravity.
* Loop quantum gravity: A non-perturbative theory of quantum gravity. "Loop gravity" or "quantum geometry". a proposed quantum theory of spacetime which attempts to reconcile the theories of quantum mechanics and general relativity. It suggests that space can be viewed as an extremely ifne fabric or network "woven" of finite quantized loops of excited gravitational fields called spin networks; viewed over time, they are called spin foam (different from quantum foam). A manor quantum gravity contender with string theory. Loop quantum gravity does not require higher dimensions.
* Immirzi parameter: A numerical coefficient appearing in loop quantum gravity.
Negative energy non-physical, left with usual graviton modes, but with a chiral asymmetry in the vacuum energy and fluctuations.
* There is no way I understood what went on in this abstract.
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