Friday. NO APARTMENT. I am going to have to extend my homeless-ness by living in a hotel for another month. Yesterday, Peter came into my office with an printout of an e-mail about two new OU-LE3 units for Euclid in Germany (Bonn & Munich). I wasn't quite sure what he wanted me to do with this information, but if he wants me to be the LE3 lead... that would be awesome.
1109.6322
Searching for DM in the CMB: a compact parameterization of energy injection from New Physics
Finkbeiner, Galli, Lin, Slatyer
CMB anisotropy set robust constraints on DM annihilation during recombination. Improve and generalize these constraints to apply to energy deposition during the recombination era with arbitrary redshift dependence [what redshift dependence did it have before?]. This approach also provides more rigorous and model-independent bounds on DM annihilation and decay scenarios. Employ principal component analysis to identify a basis of weighting functions for the energy deposition. Coefficients of these weighting functions parameterize any energy deposition model, and can be constrained directly by experiment. For generic energy deposition histories that are currently allowed by WMAP7 data, up to 3 principal component coefficients are measurable by Planck and up to 5 by an ideal cosmic variance limited experiment. For WIMP dark matter, analysis demonstrates that the effect on the CMB is described well by a single (normalization) parameter, and a "universal" redshift dependence for the energy deposition history. Give WMAP7 constraints on both generic energy deposition histories and the universal WIMP case.
* what were the results for WMAP7?
1109.6323
The road to the red sequence: a detailed view of the formation of a "red and dead" massive galaxy at z~2
Ferreras, Pasquali, Khochfar, Kuntschner, Kuemmel, Pirzkal, Windhorst, Malhotra, Rhoads, O'Connel
Spectral, morphological analysis of a star formation history in a particular galaxy. Imply cold accretion at high-z fueled efficienet star formation, subsequently stopped either by onset of a SNe-driven galactic wind, or by the merger that caused its present morphology. Implies that major mergers themselves induce the truncation of star formation in massive galaxies.
Thursday, September 29, 2011
Day 93
Thursday. Went to a Biergarten with Peter, Catherine, Tom, and Henrdik last night, at a very nice place. Aaaand, I really hope to be done with the apartment search today. Although I'm still looking, and it's already taken 2 hours of today (it's almost 10am). I should really take a shower and get to work.
MPIfR special colloquium
today MPIfR 0.02
Dynamics in young star clusters: from planets to massive stars
Christoph Olczak
How do star clusters, the building blocks of a new generation of stars and planets in galaxies, form? Use numerical simulations to study initial formation conditions and the effect of environments on formation and evolution, also talking about planet formation.
MPIfR special colloquium
today MPIfR 0.02
Dynamics in young star clusters: from planets to massive stars
Christoph Olczak
How do star clusters, the building blocks of a new generation of stars and planets in galaxies, form? Use numerical simulations to study initial formation conditions and the effect of environments on formation and evolution, also talking about planet formation.
Tuesday, September 27, 2011
Day 92
Wednesday. I hope I will find a flat today. I will take Filomena's flat if I don't like the ones I hear from, or see, today.
1109.5688
Intracluster medium of the merging cluster Abell 3395
Lakhchuaura, Singh, Saikia, Hunstead
* what it says.
1109.5690
A filamentation instability for streaming cosmic rays
Reville, Bell
Demonstrate that CRs form filamentary structures in the precursors of SNe remnant shocks due to their self-generated magnetic fields. CR filamentation results in growth of a long wavelength instability, and naturally couples the rapid non-linear amplification on small scales to larger length scales. Confirmed by a hybrid of MHD and particle simulations. Resulting large scale magnteic field may facilitate scattering of high energy CRs as required to accelerate protons beyond the knee in the CR spectrum at SNe remnant shocks. Filamentation far upstream of the shock may also assist in the escape of CRs from the accelerator.
* cool, on the origin of CRs.
1109.5691
Sample variance in photometric redshift calibration: cosmological biases and survey requirements
Cunha, Huterer, Busha, Wechsler
Use N-body+photometric galaxy simulations to examine the impact of sample variance of spectro redshift samples on the accuracy of photo-z determination and calibration of photo-z errors. Estimate bias in cosmological parameter constraints from WL and derive requirements on the spectro follow-up for 3 different photo-z algorithms, chosen to span the range of algorithms available. Find sample varinace much more relevant for photo-z error calibration than from photo-z training; follow-up requirements are similar for different algorithms. Spectro sample [presumably with cosmic variance?] can be used for training of photo-zs and error calibration without incurring additional bias in the cosmological parameters. Provide guide for observing proposals for spectroscopic follow-up; e.g., 150 patches of sky with Magellan (1/8 sqdeg field and 400 galaxies per patch) for calibrating DES, 75 nights of observation. Requirements can be reduced by an order of magnitude if the redshift distribution of the overall sample can be estimated by some other technique.
* cool. Good to check these things for the survey.
1109.5688
Intracluster medium of the merging cluster Abell 3395
Lakhchuaura, Singh, Saikia, Hunstead
* what it says.
1109.5690
A filamentation instability for streaming cosmic rays
Reville, Bell
Demonstrate that CRs form filamentary structures in the precursors of SNe remnant shocks due to their self-generated magnetic fields. CR filamentation results in growth of a long wavelength instability, and naturally couples the rapid non-linear amplification on small scales to larger length scales. Confirmed by a hybrid of MHD and particle simulations. Resulting large scale magnteic field may facilitate scattering of high energy CRs as required to accelerate protons beyond the knee in the CR spectrum at SNe remnant shocks. Filamentation far upstream of the shock may also assist in the escape of CRs from the accelerator.
* cool, on the origin of CRs.
1109.5691
Sample variance in photometric redshift calibration: cosmological biases and survey requirements
Cunha, Huterer, Busha, Wechsler
Use N-body+photometric galaxy simulations to examine the impact of sample variance of spectro redshift samples on the accuracy of photo-z determination and calibration of photo-z errors. Estimate bias in cosmological parameter constraints from WL and derive requirements on the spectro follow-up for 3 different photo-z algorithms, chosen to span the range of algorithms available. Find sample varinace much more relevant for photo-z error calibration than from photo-z training; follow-up requirements are similar for different algorithms. Spectro sample [presumably with cosmic variance?] can be used for training of photo-zs and error calibration without incurring additional bias in the cosmological parameters. Provide guide for observing proposals for spectroscopic follow-up; e.g., 150 patches of sky with Magellan (1/8 sqdeg field and 400 galaxies per patch) for calibrating DES, 75 nights of observation. Requirements can be reduced by an order of magnitude if the redshift distribution of the overall sample can be estimated by some other technique.
* cool. Good to check these things for the survey.
Day 91
Tuesday. STILL no apartment yet. Almost done with the proposal.
AIfA Bachelor Kolloquium
AIfA 0.002 28 Sept. 2011, 11am
Extinktion im interstellaren medium in M33
Karsten Spiekermann
The extinction in ISM of M33, one of the 3 spiral galaxies in the Local Group, is determined for (from?) the HII regions NGC 595 and NGC 604. For this purpose, NIR Paschen-alpha images from the WIYN High Resolution Infrared Camera (WHIRC) were reduced and combined with the H-alpha maps of KPNO Schmidt-Telescope.
* Lyman-alpha: 2 => 1 transition emission (122 nm)
* Balmer-alpha: 3 => 2 transition (656 nm)
* Paschen-alpha: 4 => 3 transition (1870 nm)
1109.5175
Nonlinear color-metallicity relations of globular clusters. II. A test on the nonlinearity scenario for color bimodality using the u-band colors: The case of M87 (NCG 4486)
Yoon, Sohn, Lee, Kim, Cho, Chung, Blakeslee
Optical color distribution of globular clusters in most large elliptical galaxies are bimodal. Linear relationship between GC colors and metallicities assumed. However, recent observations and modeling of GCs suggest color-metallicity relations (CMRs) are inflected, and hence nonlinear. The nonlinearity could produce bimodal color distributions from a broad underlying metallicity spread, even if [metallicity] is unimodal. ...Color bimodality is still an open question. Propose new photometric technique to probe possible nonlinear nature of CMRs. A color distribution of GCs is a "projected" distribution of their metallicities. Form of CMRs hinges on which color is used, shape of color distributions varies depending on the colors. Among the optical colors, the u-band related colors (u-g and u-z) are theoretically predicted to exhibit significantly less inflected CMRs than other preferred CMRs. Case study: HST archival u-band photometry for the M87 GC system with confirmed color bimodality. Show u-band color distributions are significantly different from that of g-z, and consistent with model predictions. With more u-band measurements, this methods will uspport or rule out the non-linear CMR scenario for the origin of GC color bimodality with high confidence.
1109.5175
Interpolating masked weak lensing signal with Karhunen-Loeve analysis
Vanderplas, Connoley, Jain, Jarvis
A WL systematic limitaion: incomplete coverage and pixel-level masking. Method: use 2-d KL eigenmodes of shear to interpolate noisy shear measurements across masked regions. Explore this method with simulated shear catalogs, using statistics of high-convergence regions in the resulting map. Find: not only minimizes the bias due to masked regions in the field, but also reduced spurious peak counts from shape noise by a factor of ~3 in the cosmologically sensitive regime. (!!!) Indicates KO reconstruction of masked shear not only useful for creating robust convergence maps from shear catalogs, but also offer promise of improved parameters constraints within studies of shear peak statistics.
* maybe we can use this with cluster mass estimates too...???
Sunday, September 25, 2011
Day 90
Monday. 6:00am.
1001.1737
A cosmic variance cookbook
Moster, Somerville, Newman, Rix
Deep pencil beam surveys (<1 deg. sq.) are important for studying the high-z universe, but inferences about galaxy populations properties are limited by 'cosmic variance'. Cosmic variance for a given galaxy population can be determined using predictions from CDM theory and the galaxy bias. Provide tools for experiment design and interpretation. For a given survey geometry, present the cosmic variance of DM as a function of mean redshift z and redshift bin size dz. Use HOD to predict galaxy clustering, derive galaxy bias as a function of mead redshift for galaxy samples of a given stellar mass range. In the linear regime, the cosmic variance of these galaxy samples is the product of the galaxy bias and the DM cosmic variance. Present a simple recipe using a fitting function to compute cosmic variance as a function of the angular dimensions of the field, z, dz and stellar mass m*. Also provide tabulated values and software tool. For GOODS (10'x16') at z=2 and dz=0.5, the relative cosmic variance for galaxies with m*>1e11 Msun is 38%, while it is 27% for GEMS (28'x28') and ~12% for COSMOS (84'x84'). This implies that cosmic variance is a significant source of uncertainty at z=2 for small fields and massive galaxies, while for larger fields and intermediate mass galaxies cosmic variance is less serious.
* What is the SUBARU (27'x34', close to GEMS) field variance? ... around 10% for MW galaxies or brighter. Cool!
MPIfR Special Colloquium
29 Sept. 2011, 11:00, MPIfR 0.02
Dynamiacs in young star clusters: from planets to massive stars
Christoph Olczak
Numerical simulations play a vital role in exploring the initial conditions under which star clusters form, and the impact of these (often harsh) environments on the formation and evolution of their stellar and substellar members. Stellar interactions can have a huge variety: prevent or trigger planet formation, modify disk structure, affect stellar multiplicity, leave characteristic signatures that can be traced observationally. Also, present a recently developed efficient measure of mass segregation in stellar systems. Mass segregation occurs rapidly even for spherical systems without substructure. Provides strong constraints on their initial conditions.
1001.1737
A cosmic variance cookbook
Moster, Somerville, Newman, Rix
Deep pencil beam surveys (<1 deg. sq.) are important for studying the high-z universe, but inferences about galaxy populations properties are limited by 'cosmic variance'. Cosmic variance for a given galaxy population can be determined using predictions from CDM theory and the galaxy bias. Provide tools for experiment design and interpretation. For a given survey geometry, present the cosmic variance of DM as a function of mean redshift z and redshift bin size dz. Use HOD to predict galaxy clustering, derive galaxy bias as a function of mead redshift for galaxy samples of a given stellar mass range. In the linear regime, the cosmic variance of these galaxy samples is the product of the galaxy bias and the DM cosmic variance. Present a simple recipe using a fitting function to compute cosmic variance as a function of the angular dimensions of the field, z, dz and stellar mass m*. Also provide tabulated values and software tool. For GOODS (10'x16') at z=2 and dz=0.5, the relative cosmic variance for galaxies with m*>1e11 Msun is 38%, while it is 27% for GEMS (28'x28') and ~12% for COSMOS (84'x84'). This implies that cosmic variance is a significant source of uncertainty at z=2 for small fields and massive galaxies, while for larger fields and intermediate mass galaxies cosmic variance is less serious.
* What is the SUBARU (27'x34', close to GEMS) field variance? ... around 10% for MW galaxies or brighter. Cool!
MPIfR Special Colloquium
29 Sept. 2011, 11:00, MPIfR 0.02
Dynamiacs in young star clusters: from planets to massive stars
Christoph Olczak
Numerical simulations play a vital role in exploring the initial conditions under which star clusters form, and the impact of these (often harsh) environments on the formation and evolution of their stellar and substellar members. Stellar interactions can have a huge variety: prevent or trigger planet formation, modify disk structure, affect stellar multiplicity, leave characteristic signatures that can be traced observationally. Also, present a recently developed efficient measure of mass segregation in stellar systems. Mass segregation occurs rapidly even for spherical systems without substructure. Provides strong constraints on their initial conditions.
Day 89
Sunday. Reading Friday's astro-ph.
1109.4633
Secular evolution and a non-evoloving black hole to galaxy mass ratio in the last 7 Gyr
Cisternas, Jahnke, Bongiorno, Inskip, Impey, Koekemoer, Merloni, Salvato, Trump
New constraints on the ratio of BH mass to total galaxy stellar mass at 0.3<z<0.9. Sample size of type-1 AGNs in XMM-COSMOS: 32. BH mass range: M_BH/M_sun~1e7.2 to 1e8.7, estimated from H_beta in the spectra. Estimate stellar mass from HST images of host galaxies to remove the AGN component, and using specially-built mass-to-light ratio. Find no evolution in the mass ratio M_BH/M* = (1+z)^{0.02pm0.34} up to z~0.9. There is an offset in relation to mass ratio at z=0. This can be explained by a redistribution of stellar mass to the bulge, likely driven by secular processes (i.e., internal instabilities and minor merging).
1109.4635
Hydrodynamical simulations and semi-analytic models of galaxy formation: two sides of the same coin
Neistein, Khochfar, Vecchia, Schaye
New method to turn Hydro sim into a simply SAM (semi-analytic model), by summarizing the efficiencies of accretion, cooling, star formation, and feedback from Hydro sims, as a function of halo mass and redshift. (Surprisingly) the mass of individual galaxies is conserved, with deviation at the level of 0.1 dex, with no significant systematics; true for all redshifts, and mass of stars and gas components; although the agreement reaches 0.2 dex [scatter] for stellite galaxies at low redshift. Show same level of accuracy even in case where SAM uses only one phase of gas within each galaxy [what?]. Moreover, the formation history of one massive galaxy provides sufficient information for the SAM to reproduce population of galaxies within the entire cosmological box. The reason for the small scatter between the hydro syms and SAM galaxies are: a) efficiencies are matched as functions of the halo mass and redshift, meaning that the evolution within merger-trees agrees on average. b) For a given galaxy, efficiencies fluctuate around the mean value on time scales of 0.2-2Gyr. c) The various mass components of galaxies are obtained by integrating the efficiencies over time, averaging out these fluctuations. Compare efficiencies found here to standard SAM recipes and find that they often deviate significantly. E.g., smooth accretion is less effective for low mass haloes, and is always composed of hot or dilute gas; cooling is less effective at high redshift; star formation changes only mildly with cosmic time. Recipe to convert hydro sim to SAM can be applied to any hydro sim, can thus serve as a common language between the two.
1109.4638
Moving mesh cosmology: characteristics of galaxies and halos
Kares, Vogelsberger, Sijacki, Springel, Hernquist
Moving-mesh hydro sims AREPO: investigate influence on the baryonic properties of simulated galaxies and their surrounding haloes, compared to well-tested SPH code GADGET. AREPO leads to significantly higher star formation rages for galaxies in massive haloes and more extended gaseous disks in galaxies, which also feature a thinner and smoother morphology than GADGET; AREPO have galaxies with larger sizes and higher specific angular momentum. These differences persist as a function of numerical resolution. Galaxy formation simulations greatly benefit from the use of more accurate hydro techniques such as AREPO.
1109.4640
Bayesian power spectrum analysis of interferometric data
Sutter, Wandelt, Malu
* Gibbs sampling: in statistics and statistical physics, Gibbs sampling is an algorithm to generate a sequence of samples from the joint probability distribution of two or more random variables. The purpose of such a sequence is to approximate the joint distribution; to approximate the marginal distribution of one of the variables, or some subset of the variables (e.g., the unknown parameters or latent variables); or to compute an integral (i.e., expected value of one of the variables). Typically, some of the variables correspond to observations whose values are known, and hence do not need to be sampled. Gibbs sampling is an example of MCMC algorithm.
Bayesian power spectrum and signal map inference engine which can be adapted to interferometric observations of anisotropies in CMB, 21cm emission line mapping of galactic brightness fluctuations, or 21cm absorption line mapping of neutral hydrogen in the dark ages. Method uses Gibbs sampling to generate a sampled representation of the power spectrum posterior and the posterior of signal maps given a set of measured visibilities in the uv-plane. Use mock interferometric CMB observations to demonstrate the validity of this method in the flat-sky approximation when adapted to take into account arbitrary coverage of the uv-plane, mode correlations due to observations on a finite patch, and heteroschedastic visibility errors. Computational requirements scale as O(n_p log n_p) where n_p measures the ratio of the size of the detector array to the inter-detector spacing, meaning that Gibbs sampling is a viable technique for meeting the data analysis requirements of future cosmology missions.
1109.4678
Search for Gamma-ray emission from X-ray selected Seyfert galaxies with Fermi-LAT
Fermi-LAT Collarboration
We did not find a statistically significant gamma-ray excess (TS>25) positionally coincident with any target Seyferts ('radio-quiet' objects), with 2 possible exceptions, out of 120 X-ray bright Seyfert galaxies looked into.
1109.4685
The evolution of Ly-alpha emitting galaxies between z=2.1 and z=3.1
Ciardullo, Gronwall, Wolf, McCathran, Bond, Gawiser, et al
* Heteroscedasticity: in statistics, a collection of random variables is heteroscedastic if there are sub-populations that have different variables than others. (lack of homoscedasticity, or same finite variance)
Complete sample of 141 objects in ECDF-S, remove x-ray sources and foreground objects, left with 130 LAE candidates (39 spectroscopically confirmed). Apparent anti-correlation between equivalent width and continuum brightness is likely due to the effect of correlated errors in the heteroskedastic dataset. Between z=3.1 and z=2.1 (~1Gyr), the LAE luminosity function evolved significantly, with L* fading by 0.4 mag; the number density of sources with L>1.5e43 ergs/s declining by 50%, and the equivalent width scale-length contracting from 70 to 50 Angstroms. When combined with literature results, observations demonstrate that over the redshift range z=0 to 4, LAEs contain less than 10% of the SF rate density of the universe.
1109.4690
One fewer solution to the cosmological lithium problem
Kirsebom, Davids
As the title says.
1109.4717
Supernovae without host galaxy? Hypervelocity stars in foreign galaxies
Zinn, Grunden, Bomans
Distinguish between two possible causes for SNe that apparently do not occur within a distinct host galaxy: (i) a host galaxy which is too fait to be detected, or (ii) a hypervelocity star (HVS) as progenitor of the SN. Use deep imaging to 27mag/arcsec^2 to test case (i). Out of 4 hostless SNe, find one (SN2006bx) to be put in the hypervelocity progenitor category with high probability, exhibiting a projected velocity of >800 km/s. SN is due to in situ star formation [how do they know?]
1109.4740
A highly magnified SNe at z=1.703 behind the massive galaxy cluster A1689
Ramanullah et al.
The magnification due to the cluster is 4.3 pm 0.3, allowing high z SNe lightcurves to be observed. [I guess this is the upper z limit of SNe].
1109.4820
An application of extreme value statistics to the most massive galaxy clusters at low and high redshifts
Waizmann, Ettori, Moscardini
ACT-CL J0102-4915, M200m=2e15, z=0.87
SPT-CL J2106-5844, M200m=1e15, z=1.132
XMMU J2235.32557, M200c=7e14, z=1.4
XMMU J0044.0-2033, M200c=4e14, z=1.579
None of the systems alone is in extreme tension with LCDM (ACT-CL most extreme). The high-z systems are no more extreme that the low-z systems (A2163, A370, RXJ1347-1145, 1E0657-558)
* Q: what kind of extreme value statistic did they use? A: GEV (general extreme-value statistics) in extreme value theory, concerning the stochastic behaviour of the maxima or minima of i.i.d. random variables. Gumbel 1958, Kotz&Nadarajah 2000, Coles 2001. It's not straightforward (at least, not to me).
1109.4934
Cross-correlating the thermal SZ errect and the distribution of galaxy clusters
Fang, Kadota, Takada
Stacked SZ signal: bin clusters according to their redshift and mass, then cross-correlate the tSZ effect and the galaxy clusters. This reveals the average SZ profile around the clusters. Derive error covariance matrix for measuring the stacked SZ signal, then study forecasts for its detection from combined CMB-optical surveys. Find: stacked SZ signal can be detected with a significant S/N over a wide z range; value peaks for clusters with intermediate mass and redshift. Stacking allows one to probe the clusters' SZ profiles over a wide range of scales, even out to projected radii as large as around the virial radius, hence provides a promising way to study gas physics at the outskirts of galaxy clusters.
* Done with today's astro-ph (2 hours).
1109.4633
Secular evolution and a non-evoloving black hole to galaxy mass ratio in the last 7 Gyr
Cisternas, Jahnke, Bongiorno, Inskip, Impey, Koekemoer, Merloni, Salvato, Trump
New constraints on the ratio of BH mass to total galaxy stellar mass at 0.3<z<0.9. Sample size of type-1 AGNs in XMM-COSMOS: 32. BH mass range: M_BH/M_sun~1e7.2 to 1e8.7, estimated from H_beta in the spectra. Estimate stellar mass from HST images of host galaxies to remove the AGN component, and using specially-built mass-to-light ratio. Find no evolution in the mass ratio M_BH/M* = (1+z)^{0.02pm0.34} up to z~0.9. There is an offset in relation to mass ratio at z=0. This can be explained by a redistribution of stellar mass to the bulge, likely driven by secular processes (i.e., internal instabilities and minor merging).
1109.4635
Hydrodynamical simulations and semi-analytic models of galaxy formation: two sides of the same coin
Neistein, Khochfar, Vecchia, Schaye
New method to turn Hydro sim into a simply SAM (semi-analytic model), by summarizing the efficiencies of accretion, cooling, star formation, and feedback from Hydro sims, as a function of halo mass and redshift. (Surprisingly) the mass of individual galaxies is conserved, with deviation at the level of 0.1 dex, with no significant systematics; true for all redshifts, and mass of stars and gas components; although the agreement reaches 0.2 dex [scatter] for stellite galaxies at low redshift. Show same level of accuracy even in case where SAM uses only one phase of gas within each galaxy [what?]. Moreover, the formation history of one massive galaxy provides sufficient information for the SAM to reproduce population of galaxies within the entire cosmological box. The reason for the small scatter between the hydro syms and SAM galaxies are: a) efficiencies are matched as functions of the halo mass and redshift, meaning that the evolution within merger-trees agrees on average. b) For a given galaxy, efficiencies fluctuate around the mean value on time scales of 0.2-2Gyr. c) The various mass components of galaxies are obtained by integrating the efficiencies over time, averaging out these fluctuations. Compare efficiencies found here to standard SAM recipes and find that they often deviate significantly. E.g., smooth accretion is less effective for low mass haloes, and is always composed of hot or dilute gas; cooling is less effective at high redshift; star formation changes only mildly with cosmic time. Recipe to convert hydro sim to SAM can be applied to any hydro sim, can thus serve as a common language between the two.
1109.4638
Moving mesh cosmology: characteristics of galaxies and halos
Kares, Vogelsberger, Sijacki, Springel, Hernquist
Moving-mesh hydro sims AREPO: investigate influence on the baryonic properties of simulated galaxies and their surrounding haloes, compared to well-tested SPH code GADGET. AREPO leads to significantly higher star formation rages for galaxies in massive haloes and more extended gaseous disks in galaxies, which also feature a thinner and smoother morphology than GADGET; AREPO have galaxies with larger sizes and higher specific angular momentum. These differences persist as a function of numerical resolution. Galaxy formation simulations greatly benefit from the use of more accurate hydro techniques such as AREPO.
1109.4640
Bayesian power spectrum analysis of interferometric data
Sutter, Wandelt, Malu
* Gibbs sampling: in statistics and statistical physics, Gibbs sampling is an algorithm to generate a sequence of samples from the joint probability distribution of two or more random variables. The purpose of such a sequence is to approximate the joint distribution; to approximate the marginal distribution of one of the variables, or some subset of the variables (e.g., the unknown parameters or latent variables); or to compute an integral (i.e., expected value of one of the variables). Typically, some of the variables correspond to observations whose values are known, and hence do not need to be sampled. Gibbs sampling is an example of MCMC algorithm.
Bayesian power spectrum and signal map inference engine which can be adapted to interferometric observations of anisotropies in CMB, 21cm emission line mapping of galactic brightness fluctuations, or 21cm absorption line mapping of neutral hydrogen in the dark ages. Method uses Gibbs sampling to generate a sampled representation of the power spectrum posterior and the posterior of signal maps given a set of measured visibilities in the uv-plane. Use mock interferometric CMB observations to demonstrate the validity of this method in the flat-sky approximation when adapted to take into account arbitrary coverage of the uv-plane, mode correlations due to observations on a finite patch, and heteroschedastic visibility errors. Computational requirements scale as O(n_p log n_p) where n_p measures the ratio of the size of the detector array to the inter-detector spacing, meaning that Gibbs sampling is a viable technique for meeting the data analysis requirements of future cosmology missions.
1109.4678
Search for Gamma-ray emission from X-ray selected Seyfert galaxies with Fermi-LAT
Fermi-LAT Collarboration
We did not find a statistically significant gamma-ray excess (TS>25) positionally coincident with any target Seyferts ('radio-quiet' objects), with 2 possible exceptions, out of 120 X-ray bright Seyfert galaxies looked into.
1109.4685
The evolution of Ly-alpha emitting galaxies between z=2.1 and z=3.1
Ciardullo, Gronwall, Wolf, McCathran, Bond, Gawiser, et al
* Heteroscedasticity: in statistics, a collection of random variables is heteroscedastic if there are sub-populations that have different variables than others. (lack of homoscedasticity, or same finite variance)
Complete sample of 141 objects in ECDF-S, remove x-ray sources and foreground objects, left with 130 LAE candidates (39 spectroscopically confirmed). Apparent anti-correlation between equivalent width and continuum brightness is likely due to the effect of correlated errors in the heteroskedastic dataset. Between z=3.1 and z=2.1 (~1Gyr), the LAE luminosity function evolved significantly, with L* fading by 0.4 mag; the number density of sources with L>1.5e43 ergs/s declining by 50%, and the equivalent width scale-length contracting from 70 to 50 Angstroms. When combined with literature results, observations demonstrate that over the redshift range z=0 to 4, LAEs contain less than 10% of the SF rate density of the universe.
1109.4690
One fewer solution to the cosmological lithium problem
Kirsebom, Davids
As the title says.
1109.4717
Supernovae without host galaxy? Hypervelocity stars in foreign galaxies
Zinn, Grunden, Bomans
Distinguish between two possible causes for SNe that apparently do not occur within a distinct host galaxy: (i) a host galaxy which is too fait to be detected, or (ii) a hypervelocity star (HVS) as progenitor of the SN. Use deep imaging to 27mag/arcsec^2 to test case (i). Out of 4 hostless SNe, find one (SN2006bx) to be put in the hypervelocity progenitor category with high probability, exhibiting a projected velocity of >800 km/s. SN is due to in situ star formation [how do they know?]
1109.4740
A highly magnified SNe at z=1.703 behind the massive galaxy cluster A1689
Ramanullah et al.
The magnification due to the cluster is 4.3 pm 0.3, allowing high z SNe lightcurves to be observed. [I guess this is the upper z limit of SNe].
1109.4820
An application of extreme value statistics to the most massive galaxy clusters at low and high redshifts
Waizmann, Ettori, Moscardini
ACT-CL J0102-4915, M200m=2e15, z=0.87
SPT-CL J2106-5844, M200m=1e15, z=1.132
XMMU J2235.32557, M200c=7e14, z=1.4
XMMU J0044.0-2033, M200c=4e14, z=1.579
None of the systems alone is in extreme tension with LCDM (ACT-CL most extreme). The high-z systems are no more extreme that the low-z systems (A2163, A370, RXJ1347-1145, 1E0657-558)
* Q: what kind of extreme value statistic did they use? A: GEV (general extreme-value statistics) in extreme value theory, concerning the stochastic behaviour of the maxima or minima of i.i.d. random variables. Gumbel 1958, Kotz&Nadarajah 2000, Coles 2001. It's not straightforward (at least, not to me).
1109.4934
Cross-correlating the thermal SZ errect and the distribution of galaxy clusters
Fang, Kadota, Takada
Stacked SZ signal: bin clusters according to their redshift and mass, then cross-correlate the tSZ effect and the galaxy clusters. This reveals the average SZ profile around the clusters. Derive error covariance matrix for measuring the stacked SZ signal, then study forecasts for its detection from combined CMB-optical surveys. Find: stacked SZ signal can be detected with a significant S/N over a wide z range; value peaks for clusters with intermediate mass and redshift. Stacking allows one to probe the clusters' SZ profiles over a wide range of scales, even out to projected radii as large as around the virial radius, hence provides a promising way to study gas physics at the outskirts of galaxy clusters.
* Done with today's astro-ph (2 hours).
Saturday, September 24, 2011
Day 88
Saturday. Here begins my daily prayer (11:46 am). Daily prayers at the beginning of the day (i.e., 6am) is better, as I did yesterday.
MPIfR Lunch Colloquium
MPIfR 0.02, Sept 28, 13:00
Structure of hot molecular cores
Rainer Rolffs
Hot molecular cores: transient phase of high-mass star formation (heated up, but before being ionized). Intro to high-mass star formation; present observation (APEX/Herschel, VLA/SMA) and analysis (spherical radiative transfer and 3-d modeling) methods; highlight results. Mass of hot molecular gas, internal heating mechanism (radiation diffusion), infall reversal in the central region, centrally flat density distribution. All can be explained by increased central pressure caused by feedback from young massive stars in a high-column-density environment.
AIfA Master-Kolloquium
AIfA 0.012, 29 Sept. 2011, 11:00
Constraints on the "Universal" Pressure Profile through the SZ power spectrum
Miriam Elizabeth Ramos Ceja
* I've read this one before.
MPIfR Lunch Colloquium
MPIfR 0.02, Sept 28, 13:00
Structure of hot molecular cores
Rainer Rolffs
Hot molecular cores: transient phase of high-mass star formation (heated up, but before being ionized). Intro to high-mass star formation; present observation (APEX/Herschel, VLA/SMA) and analysis (spherical radiative transfer and 3-d modeling) methods; highlight results. Mass of hot molecular gas, internal heating mechanism (radiation diffusion), infall reversal in the central region, centrally flat density distribution. All can be explained by increased central pressure caused by feedback from young massive stars in a high-column-density environment.
AIfA Master-Kolloquium
AIfA 0.012, 29 Sept. 2011, 11:00
Constraints on the "Universal" Pressure Profile through the SZ power spectrum
Miriam Elizabeth Ramos Ceja
* I've read this one before.
Thursday, September 22, 2011
Day 87
Friday. My happiness is depending too much on finding a good place to live in Bonn. I'm going to have to rely on Ellen and Laura's help (and of many others) to get me through this apartment hunting (and stop killing myself over this).
1109.4632
A new cosmological distance measure using AGN
Watson, Denny, Vestergaard, Davis
Discovery of an accurate luminosity distance measure using AGN: Use the tight relationship between the luminosity of an AGN and the radius of its broad line region established via reverberation mapping to determine the luminosity distances to a sample of 38 AGN. All reliable distance measures have (up to now) been limited to moderate redshifts; AGN will allow distances to be estimated to z~4, where variations of DE and alternate gravity theories can be probed.
2.1) reverberation mapping:
* Physics: SMBH is surrounded at a distance by high velocity gas clouds that produce the broad emission lines characteristic of the spectra of near-face-on AGN (quasars and Seyfert 1 galaxies). Size of BLR is determined by the depth to which the surrounding gas can be photo-ionized by the central source. Ionizing flux drops with distance according to the inverse square law, so the radius of the BLR (broad-line emitting region), "r", is expected to be proportional to the square root of the luminosity L. Establish r and the flux to measure luminosity distance.
* Method: Photons emitted by GLR gas are reprocessed continuum photons; the flux in the broad lines varies in response to variations in the luminosity of the central source with a time-delay, tau, governed by the light travel time, tau=r/c. Measuring the time delay thus allows a determination of the BLR radius--i.e., "reverberation mapping". Radius is effectively determined by measuring the time lag between changes in the continuum luminosity of the AGN and the luminosity of a bright emission line.
* Systematics: luminosities: remove the contaminating effects of the host galaxy. lag: reobserving AGN with previously had poorly sampled light-curves. Populating the low luminosity regime of the existing sample. The r ~ sqrt(L) relation followed to good accuracy (how good?) for 4 orders of magnitude in luminosity.
3.) Data
* important to remove host galaxy component; done primarily using images from HST to model the underlying galaxy contribution (i.e., it's expensive). (It doesn't say exactly how)
* some AGNs are close enough to be directly calibrated by Cepheids.
4.) Results
* rms scatter in AGN Hubble diagram: 0.2 dex (0.5 mag in distance modulus). Observational uncertainty account for ~50% of the total scatter in the relation, or 0.14 dex (0.36 mag).
* repeated observation of given sources will reduce the scatter related to observational uncertainty to a level of NGC5548 (i.e., ~<0.3 mag).
* extinction can be measured (and hence corrected for) using the "Balmer decrement metnod, Na I D or K I line equivalent widths, or a calibration based on several methods. Scatter here can be lowered from the current 0.2 mag to 0.1 mag.
* possible improvements in lag measurements. past lag measurements are likely to be less uncertain
5) Discussion
* Prospects for extension to high z: it's much brighter than SNe, so can go to z~4; but requires longer temporal baselines (redshift time dilation + brighter (and hence larger r) AGNs). Time lags can be ~2 years for AGN at z~2. Different lines have different lags (apparently) though. Some lines don't require host correction (i.e., C IV). But is less resource intensive because the lightcurve can be measured over a long time (i.e., leisurely).
* AGN method may not require calibration to absolute distances, like SNe.
* Intrinsic diversity: Assumed constant ionisation parameters across the sample--requires density close to the same value in a given region of the BLR across sources. ** the ultimate limit to the accuracy of AGN Hubble diagram. (degree unknown; current measurements have larger scatter)
* Competitiveness: should be achievable in less than a decade at redshifts up to z=3.
1109.4632
A new cosmological distance measure using AGN
Watson, Denny, Vestergaard, Davis
Discovery of an accurate luminosity distance measure using AGN: Use the tight relationship between the luminosity of an AGN and the radius of its broad line region established via reverberation mapping to determine the luminosity distances to a sample of 38 AGN. All reliable distance measures have (up to now) been limited to moderate redshifts; AGN will allow distances to be estimated to z~4, where variations of DE and alternate gravity theories can be probed.
2.1) reverberation mapping:
* Physics: SMBH is surrounded at a distance by high velocity gas clouds that produce the broad emission lines characteristic of the spectra of near-face-on AGN (quasars and Seyfert 1 galaxies). Size of BLR is determined by the depth to which the surrounding gas can be photo-ionized by the central source. Ionizing flux drops with distance according to the inverse square law, so the radius of the BLR (broad-line emitting region), "r", is expected to be proportional to the square root of the luminosity L. Establish r and the flux to measure luminosity distance.
* Method: Photons emitted by GLR gas are reprocessed continuum photons; the flux in the broad lines varies in response to variations in the luminosity of the central source with a time-delay, tau, governed by the light travel time, tau=r/c. Measuring the time delay thus allows a determination of the BLR radius--i.e., "reverberation mapping". Radius is effectively determined by measuring the time lag between changes in the continuum luminosity of the AGN and the luminosity of a bright emission line.
* Systematics: luminosities: remove the contaminating effects of the host galaxy. lag: reobserving AGN with previously had poorly sampled light-curves. Populating the low luminosity regime of the existing sample. The r ~ sqrt(L) relation followed to good accuracy (how good?) for 4 orders of magnitude in luminosity.
3.) Data
* important to remove host galaxy component; done primarily using images from HST to model the underlying galaxy contribution (i.e., it's expensive). (It doesn't say exactly how)
* some AGNs are close enough to be directly calibrated by Cepheids.
4.) Results
* rms scatter in AGN Hubble diagram: 0.2 dex (0.5 mag in distance modulus). Observational uncertainty account for ~50% of the total scatter in the relation, or 0.14 dex (0.36 mag).
* repeated observation of given sources will reduce the scatter related to observational uncertainty to a level of NGC5548 (i.e., ~<0.3 mag).
* extinction can be measured (and hence corrected for) using the "Balmer decrement metnod, Na I D or K I line equivalent widths, or a calibration based on several methods. Scatter here can be lowered from the current 0.2 mag to 0.1 mag.
* possible improvements in lag measurements. past lag measurements are likely to be less uncertain
5) Discussion
* Prospects for extension to high z: it's much brighter than SNe, so can go to z~4; but requires longer temporal baselines (redshift time dilation + brighter (and hence larger r) AGNs). Time lags can be ~2 years for AGN at z~2. Different lines have different lags (apparently) though. Some lines don't require host correction (i.e., C IV). But is less resource intensive because the lightcurve can be measured over a long time (i.e., leisurely).
* AGN method may not require calibration to absolute distances, like SNe.
* Intrinsic diversity: Assumed constant ionisation parameters across the sample--requires density close to the same value in a given region of the BLR across sources. ** the ultimate limit to the accuracy of AGN Hubble diagram. (degree unknown; current measurements have larger scatter)
* Competitiveness: should be achievable in less than a decade at redshifts up to z=3.
Tuesday, September 20, 2011
Day 86
Tuesday. Must finish Reina's paper review. I still don't have an apartment! It's getting depressing.
1109.3708
Observational constraints on the redshift evolution of X-ray scaling relations of galaxy clusters out to z~1.5
Reichert, Böhringer, Fassbender, Mühlegger
Current literature provides a diverse and inhomogeneous picture of scaling relation evolution. Provide overall view of scaling relation evolution with recently discovered high-z cluster; normalize with other cluster data. Study M-T, Lx-T, and M-Lx relation combining 14 published data sets supplemented with recently published data of distant clusters and new results from follow-up observations of the XMM-Newton Distant Cluster Project (XDCP). Find: evolution of the M-T relation is consistent with self-similar prediction, while evolution of X-ray luminosity for a given temperature and mass for a given X-ray luminosity is slower than predicted. Best fit results for the evolution factor E(z)^alpha are alpha=-1.04pm0.07 for the M-T relation, alpha=-0.23p0.12m0.62 for the L-T relation, and alpha=-0.93p0.62m0.12 for the M-Lx relation. Find that selection biases are the most likely reason for apparent inconsistencies between different published data sets. New results provide the most robust calibration high-z cluster mass estimates based on X-ray luminosity and temperature; helps improve the prediction of the number of clusters to be found in future galaxy cluster X-ray surveys, such as eROSITA. Comparison of evolution results with hydrodynamical cosmological simulations suggests that early preheating of the ICM provides the most suitable scenario to explain the observed evolution.
* I want to read this paper and get the physical picture.
1109.3709
On the cluster physics of SZ surveys I: the influence of feedback, non-thermal pressure and cluster shapes on Y-M scaling relations
Battaglia, Bond, Pfrommer, Sievers
Y-M relation = SZ-flux-to-mass relation. Explore how non-thermal pressure and anisotropic shape of the gas distribution of the ICM impacts Y-M scaling using SPH simulations. Contrast results for models with different treatments of entropy injection and transport (radiative cooling, star formation and accompanying SNe feedback, cosmic rays, energetic feedback from AGN). The gas kinetic-to-thermal pressure ratio from internal bulk motions depends on the cluster mass, and increases in the outer-cluster due to enhanced substructure, as does the asphericity of the ICM gas. 3D ellipticities can be inferred from the observed (projected) ellipticity. Simulated Y-M slope roughly follows the self-similar prediction, except for a steepening due to a deficit of gas in lower mass clusters at low redshift in simulations with AGN feedback. AGN feedback enhances the overall Y-M scatter by 2% to 13%, a reflection of accretion history variations due to cluster merging. If we split the cluster system into lower, middle and upper bands of both P_kin/P_th and long-to-short axis ratio, find a ~10% effect on Y-M. Identifying observable second parameters related to internal bulk flows and anisotropy for cluster-selection to minimize Y-M scatter in a "fundamental plane" would allow tighter cosmological parameter constraints.
1109.3711
On the cluster physics of SZ surveys II: Deconstructing the thermal SZ power spectrum
Battaglia, Bond, Pfrommer, Sievers
CMB secondary anisotropies resulting from tSZ--its amplitude depends critically on the average thermal pressure profile of galaxy groups and clusters. Use a suite of SPH simulations that include radiative cooling, star formation, SNe, and AGN feedback. Examine in detail how the pressure profile depends on cluster radius, mass, and redshift and provide and empirical fitting function. Employ three different approaches for calculating the tSZ power spectrum Analytical that uses pressure profile fit; semi-analytical method of pasting pressure fit onto simulated clusters, and direct numerical integration of the simulated volumes. Demonstrate that the detailed structure of the intracluster medium and cosmic web affect the tSZ power spectrum. Particularly: the substructure and asphericity of the clusters increase the tSZ power spectrum by 10-20% at l=2000-8000, with most of the additional power being contributed by substructures. Contributions to the power spectrum from radii larger than R_500 is ~20% at l=3000, thus cluster interiors (r<R_500) dominated the power spectrum amplitude at these angular scales.
1109.3713
The origin of metals in the circum-galactic medium of massive galaxies at z=3
Shen, Madau, Aguirre, Guedes, Mayer, Wadsley
Detailed study of the metal-enriched circum-galactic medium of a massive galaxy at z=3 from the "Eris" suite of new cosmological hydrodynamic "zoom-in" simulations in whch a close analog of a MW disk galaxy arises at the present epoch. At z=3, the main progenitor resembles a Ly-break galaxy of M_vir=2.4e11 solar mass and r_vir=48kpc, with SFR 18 Msun/yr, and its metal-enriched CGM (?) extends as far as 200 (physical) kpc from its center. 41% hot (T>3e5K), 9% warm (2e5>T>3e4K), 50% cold (T<3e4K) gas-phase metals. Main host is responsible for 60% of all metals found within 3r_vir; satellite progenitors give origin to 28% and 5% of all metals within and beyond 3r_vir, respectively; satellite dwarf companions give origin to 12% and 95%, respectively. Late (z<5) superwinds account for only 9% of all the metals observed beyond 2r_vir, the bulk having been released at redshifts 5<z<8 by early SF and outflows. In the IGM, lower overdensities are typically enriched by 'older', colder metals. Heavy elements are accreted onto Eris along filaments via low-metallicity cold inflows, and are ejected hot via galactic outflows at a few hundred km/s. The outflow mass-loading factor as a function of redshift ranges between 0.1 and 1.2, and shows no correlation with the mass of the host.
1109.3708
Observational constraints on the redshift evolution of X-ray scaling relations of galaxy clusters out to z~1.5
Reichert, Böhringer, Fassbender, Mühlegger
Current literature provides a diverse and inhomogeneous picture of scaling relation evolution. Provide overall view of scaling relation evolution with recently discovered high-z cluster; normalize with other cluster data. Study M-T, Lx-T, and M-Lx relation combining 14 published data sets supplemented with recently published data of distant clusters and new results from follow-up observations of the XMM-Newton Distant Cluster Project (XDCP). Find: evolution of the M-T relation is consistent with self-similar prediction, while evolution of X-ray luminosity for a given temperature and mass for a given X-ray luminosity is slower than predicted. Best fit results for the evolution factor E(z)^alpha are alpha=-1.04pm0.07 for the M-T relation, alpha=-0.23p0.12m0.62 for the L-T relation, and alpha=-0.93p0.62m0.12 for the M-Lx relation. Find that selection biases are the most likely reason for apparent inconsistencies between different published data sets. New results provide the most robust calibration high-z cluster mass estimates based on X-ray luminosity and temperature; helps improve the prediction of the number of clusters to be found in future galaxy cluster X-ray surveys, such as eROSITA. Comparison of evolution results with hydrodynamical cosmological simulations suggests that early preheating of the ICM provides the most suitable scenario to explain the observed evolution.
* I want to read this paper and get the physical picture.
1109.3709
On the cluster physics of SZ surveys I: the influence of feedback, non-thermal pressure and cluster shapes on Y-M scaling relations
Battaglia, Bond, Pfrommer, Sievers
Y-M relation = SZ-flux-to-mass relation. Explore how non-thermal pressure and anisotropic shape of the gas distribution of the ICM impacts Y-M scaling using SPH simulations. Contrast results for models with different treatments of entropy injection and transport (radiative cooling, star formation and accompanying SNe feedback, cosmic rays, energetic feedback from AGN). The gas kinetic-to-thermal pressure ratio from internal bulk motions depends on the cluster mass, and increases in the outer-cluster due to enhanced substructure, as does the asphericity of the ICM gas. 3D ellipticities can be inferred from the observed (projected) ellipticity. Simulated Y-M slope roughly follows the self-similar prediction, except for a steepening due to a deficit of gas in lower mass clusters at low redshift in simulations with AGN feedback. AGN feedback enhances the overall Y-M scatter by 2% to 13%, a reflection of accretion history variations due to cluster merging. If we split the cluster system into lower, middle and upper bands of both P_kin/P_th and long-to-short axis ratio, find a ~10% effect on Y-M. Identifying observable second parameters related to internal bulk flows and anisotropy for cluster-selection to minimize Y-M scatter in a "fundamental plane" would allow tighter cosmological parameter constraints.
1109.3711
On the cluster physics of SZ surveys II: Deconstructing the thermal SZ power spectrum
Battaglia, Bond, Pfrommer, Sievers
CMB secondary anisotropies resulting from tSZ--its amplitude depends critically on the average thermal pressure profile of galaxy groups and clusters. Use a suite of SPH simulations that include radiative cooling, star formation, SNe, and AGN feedback. Examine in detail how the pressure profile depends on cluster radius, mass, and redshift and provide and empirical fitting function. Employ three different approaches for calculating the tSZ power spectrum Analytical that uses pressure profile fit; semi-analytical method of pasting pressure fit onto simulated clusters, and direct numerical integration of the simulated volumes. Demonstrate that the detailed structure of the intracluster medium and cosmic web affect the tSZ power spectrum. Particularly: the substructure and asphericity of the clusters increase the tSZ power spectrum by 10-20% at l=2000-8000, with most of the additional power being contributed by substructures. Contributions to the power spectrum from radii larger than R_500 is ~20% at l=3000, thus cluster interiors (r<R_500) dominated the power spectrum amplitude at these angular scales.
1109.3713
The origin of metals in the circum-galactic medium of massive galaxies at z=3
Shen, Madau, Aguirre, Guedes, Mayer, Wadsley
Detailed study of the metal-enriched circum-galactic medium of a massive galaxy at z=3 from the "Eris" suite of new cosmological hydrodynamic "zoom-in" simulations in whch a close analog of a MW disk galaxy arises at the present epoch. At z=3, the main progenitor resembles a Ly-break galaxy of M_vir=2.4e11 solar mass and r_vir=48kpc, with SFR 18 Msun/yr, and its metal-enriched CGM (?) extends as far as 200 (physical) kpc from its center. 41% hot (T>3e5K), 9% warm (2e5>T>3e4K), 50% cold (T<3e4K) gas-phase metals. Main host is responsible for 60% of all metals found within 3r_vir; satellite progenitors give origin to 28% and 5% of all metals within and beyond 3r_vir, respectively; satellite dwarf companions give origin to 12% and 95%, respectively. Late (z<5) superwinds account for only 9% of all the metals observed beyond 2r_vir, the bulk having been released at redshifts 5<z<8 by early SF and outflows. In the IGM, lower overdensities are typically enriched by 'older', colder metals. Heavy elements are accreted onto Eris along filaments via low-metallicity cold inflows, and are ejected hot via galactic outflows at a few hundred km/s. The outflow mass-loading factor as a function of redshift ranges between 0.1 and 1.2, and shows no correlation with the mass of the host.
Monday, September 19, 2011
Day 85
Monday. Hope to get back into the swing of things (in research).
1109.3460
Testing scaling relations for solar-like oscillations from the main sequence to red giants using Kepler data
Huber et al.
* what is a "solar-like oscillation"? --Astroseismic activity, it seems.
~1700 main-to-red stars from Kepler. Use evolutionary models to test astroseismic scaling relations for the frequency of maximum power (nu_max), the large frequency separation (Delta_nu) and oscillation amplitudes. Difference in the Delta-nu-nu_max relation for unevolved and evolved stars can be explained by different distributions in effective temperature and stellar mass, in agreement with scaling relations (but not for red giant stars). Revised scaling relation with separate luminosity-mass dependence can be used to calculate amplitudes from main-sequence to red-giants to a precision of ~25%. Investigate correlations between amplitudes and stellar activity; find evidence that amplitude suppression is most pronounced for subgiant stars. Test location of cool edge of the instability strip in the HR diagram using solar-like oscillations and find the detections in the hottest stars [are] compatible with domain of stochastically excited and opacity driven pulsation.
1109.3461
Search for z~7 Ly-alpha emitters with Suprime-Cam at the Subaru Telescope
Hibon, Kashikawa, Willott, Iye, Shibuya
Search for z=7 LAE using custom-made narrow band filter at 9755A on Suprime-cam. Two fields, 7 candidates, 4 robust. Derive possible z~7 Ly-alpha luminosity functions for the full samples and for a subsample of 4 objects in each field. No strong evolution between the z=6.5 and 7 LyA luminosity functions. Spectroscopic confirmation for the candidate samples required for a definitive measure of luminosity function at z~7.
1109.3458
Modelling larg-scale halo bias using the bispectrum
Pollack, Smith, Porciani
Study halo bias in LCDM, quadratic order in matter density, characterized by b1 and b2. Estimate parameters using N-body simulations. Smooth both matter and halo: bias parameters vary by smoothing scale. Real space has no parameters independent of smoothing. In Fourier space: measure halo power spectra, construct estimates for effective large-scale bias. Measure configuration dependence of the halo bispectra B_hhh and reduced bispectra Q_hhh for very large-scale k-space triangles (is this small k?). Constrain b_1 and b_2 from these. For B_hhh the best-fit parameters are in reasonable agreement with lowest-order perturbation theory as the triangle scale is varied, but poor as smaller scales are included; similar for Q_hhh. For k1>0.03h/Mpc, Results for B_hhh and Q_hhh are incompatible. "Discreteness correction" dependence seen in best-fit parameters. Consider halo-mass cross-bispectra; results support earlier findings. Develop a test to explore significance of higher-order terms in the models. Low order expansions are not able to correctly model the data, even for k1~0.04h/Mpc. If robust references drawn are to be drawn from galaxy surveys, then accurate models for the full nonlinear matter bispectrum and trispectrum will be essential (?).
1109.3460
Testing scaling relations for solar-like oscillations from the main sequence to red giants using Kepler data
Huber et al.
* what is a "solar-like oscillation"? --Astroseismic activity, it seems.
~1700 main-to-red stars from Kepler. Use evolutionary models to test astroseismic scaling relations for the frequency of maximum power (nu_max), the large frequency separation (Delta_nu) and oscillation amplitudes. Difference in the Delta-nu-nu_max relation for unevolved and evolved stars can be explained by different distributions in effective temperature and stellar mass, in agreement with scaling relations (but not for red giant stars). Revised scaling relation with separate luminosity-mass dependence can be used to calculate amplitudes from main-sequence to red-giants to a precision of ~25%. Investigate correlations between amplitudes and stellar activity; find evidence that amplitude suppression is most pronounced for subgiant stars. Test location of cool edge of the instability strip in the HR diagram using solar-like oscillations and find the detections in the hottest stars [are] compatible with domain of stochastically excited and opacity driven pulsation.
1109.3461
Search for z~7 Ly-alpha emitters with Suprime-Cam at the Subaru Telescope
Hibon, Kashikawa, Willott, Iye, Shibuya
Search for z=7 LAE using custom-made narrow band filter at 9755A on Suprime-cam. Two fields, 7 candidates, 4 robust. Derive possible z~7 Ly-alpha luminosity functions for the full samples and for a subsample of 4 objects in each field. No strong evolution between the z=6.5 and 7 LyA luminosity functions. Spectroscopic confirmation for the candidate samples required for a definitive measure of luminosity function at z~7.
Sunday, September 18, 2011
Day 83
Friday. More apartment searching... but no appointment to see today.
1109.2082
A new approach to cosmological perturbations in f(R) models
Bertacca, Bartolo, Matarrese
Method to quantitatively determine the deviation in the behaviour of cosmological perturbations between f(R) gravity and LCDM reference. Allows study of structure formation in these models from the largest scales, down to scales deeply inside Hubble radius (without employing the "quasi-static" approximation) (?). Analysis restricted to linear perturbations, but the technique is completely general and can be extended to any perturbative order.
Day 84
Sunday. Went and saw SOFIA at Köln today! 4 hour wait, but was worth it. Saw the A380 take off, and "wave" (tilt a low altitude flying) at us. Had dinner in Bonn with Dandan and Ralph; encountered a spectacular water-fountain show.
AIfA Master-Kolloquium
Decomposition of the matter power spectrum
Richard Hanson
Environmental effects of the matter and halo power spectra. Halo-biasing depends on halo-mass (well known) as well as scale and environment. Separate knots, filaments, sheets and voids: four characteristic environments. Further aspects of the method highlighted.
1109.2314
Does the growth of structure affect out dynamical models of the universe? The averaging, backreaction and fitting problems in cosmology
Clarkson, Ellis, Larena, Umeh
* backreaction: a modification of the original environment due to the probe particle carrying a mass and charge itself. In theoretical physics, back-reaction is often necessary to calculate the behavior of a particle in an external field. In cosmology the term is used for the measure of the non-commutativity of the averaging procedure and the dynamical evolution of space-time; existence of isotropy scale determined by the length scale at which back-reaction parameter vanishes. Existence of (cosmological) back-reaction scale still needs experimental confirmation.
Important problem for cosmology: determining the influence the small-scale structure in the universe has on its large-scale dynamics and observations. One issue: whether process of smoothing over structure can contribute to an acceleration term and alter the apparent value of the cosmological constant. Are there any other aspects of concordance cosmology that are affected by backreaction effects? This 'averaging problem' is still unanswered, but cannot be ignored in precision cosmology.
* basically just states the issue, no resolutions here.
1109.2484
Interpreting supernovae observations in a lumpy universe
Clarkson, Ellis, Faltenbacher, Maartens, Umeh, Uzan
How does may beam (i.e., the light from SNe) averages of Weyl curvature into the Ricci curvature of the background? This is not understood. Incorrect modeling leads to significant changes to the inferred background cosmology. Standard analysis predict a huge variance for small beam sizes; non-linear corrections appear to be non-trivial. Different reasonable apporximations yield very different cosmologies; modelling ultra-narrow beams accurately is a critical problem for precision cosmology.
* this is true for WL cosmic shear too, most likely.
AIfA Master-Kolloquium
Decomposition of the matter power spectrum
Richard Hanson
Environmental effects of the matter and halo power spectra. Halo-biasing depends on halo-mass (well known) as well as scale and environment. Separate knots, filaments, sheets and voids: four characteristic environments. Further aspects of the method highlighted.
1109.2314
Does the growth of structure affect out dynamical models of the universe? The averaging, backreaction and fitting problems in cosmology
Clarkson, Ellis, Larena, Umeh
* backreaction: a modification of the original environment due to the probe particle carrying a mass and charge itself. In theoretical physics, back-reaction is often necessary to calculate the behavior of a particle in an external field. In cosmology the term is used for the measure of the non-commutativity of the averaging procedure and the dynamical evolution of space-time; existence of isotropy scale determined by the length scale at which back-reaction parameter vanishes. Existence of (cosmological) back-reaction scale still needs experimental confirmation.
Important problem for cosmology: determining the influence the small-scale structure in the universe has on its large-scale dynamics and observations. One issue: whether process of smoothing over structure can contribute to an acceleration term and alter the apparent value of the cosmological constant. Are there any other aspects of concordance cosmology that are affected by backreaction effects? This 'averaging problem' is still unanswered, but cannot be ignored in precision cosmology.
* basically just states the issue, no resolutions here.
1109.2484
Interpreting supernovae observations in a lumpy universe
Clarkson, Ellis, Faltenbacher, Maartens, Umeh, Uzan
How does may beam (i.e., the light from SNe) averages of Weyl curvature into the Ricci curvature of the background? This is not understood. Incorrect modeling leads to significant changes to the inferred background cosmology. Standard analysis predict a huge variance for small beam sizes; non-linear corrections appear to be non-trivial. Different reasonable apporximations yield very different cosmologies; modelling ultra-narrow beams accurately is a critical problem for precision cosmology.
* this is true for WL cosmic shear too, most likely.
Thursday, September 15, 2011
Day 82
Thursday. I want to go through astro-ph for the past 2-3 days, so that I can join in the conversation of Christiano's group tomorrow. I also want to start a cosmology astro-ph with Laura. Housing search is moving along--I have sent an application to an apartment right along the Rhine (Rheins, in Deutsch), but it's a bit expensive there.... I'm hoping to find a cheaper place that I would like to live in (center city would be nice).
1109.2056
The orientation of disk galaxies around large cosmic voids
Varela, Betancort-Rijo, Trujillo, Ricciardelli
Using SDSS7, find large voids, and surrounding sprials. For large voids (r > 15Mpc/h), sprials w/in 5Mpc/h shell have ~2sigma significance of angular momentum aligned in the radial direction of the void. For r<15Mpc/h, the alignment is consistent with random. Alignment strength dependent on distance from void surface. Galaxy alignment trend observed similar to minor axis of DM halos around cosmic voids found in cosmological simulations, suggesting possible link in the evolution of both components.
1109.2056
The orientation of disk galaxies around large cosmic voids
Varela, Betancort-Rijo, Trujillo, Ricciardelli
Using SDSS7, find large voids, and surrounding sprials. For large voids (r > 15Mpc/h), sprials w/in 5Mpc/h shell have ~2sigma significance of angular momentum aligned in the radial direction of the void. For r<15Mpc/h, the alignment is consistent with random. Alignment strength dependent on distance from void surface. Galaxy alignment trend observed similar to minor axis of DM halos around cosmic voids found in cosmological simulations, suggesting possible link in the evolution of both components.
Wednesday, September 14, 2011
Day 81
Wednesday. I so want to be done with the apartment hunting. Last night was a disappointment--a beautiful house on Glückstraße, but not enough privacy.
1109.1821
The CFHTLS-Strong lensing legacy survey (SL2S): investigating the group-scale lenses with the SARCS sample
More, Cabanac, More, Alard, Limousin, Kneib, Gavazzi, Motta
Use of semi-automatic method to find gravitational arcs, visual inspection-pruned. 54 systems, 12 giant arcs, 2 radial arcs. Sytematic alignment of giant arcs with the ellipticity of the baryonic component of the lens. Lens redshift distribution of arcs (estimated from photometry) peaks at z~0.5. Largest lens sample probing group-scales for the first time. Compare observed image separation distribution with theoretical models: ISD accommodate models with both with and without adiabatic contraction (probably need more samples, yah?). (indeed,) Large sample might constrain relations such as the concentration-mass relation, mass-luminosity relation and slope of the luminosity function.
1109.1828
The XMM Cluster Survey: predicted overlap with the Planck Cluster Catalogue
Viana, da Silva, Ramos, Liddle, Lloyd-Davies, Romer, Kay, Collins, Hilton, Hosmer, Hoyle, Mehrtens, Miller, Sahlan, Stanford, Stott
Present serendipitously-discovered 15 clusters of galaxies in XCS that have high detection probability by Planck (3 of which already appear in the Planck Early SZ (ESZ) catalogue. Detection probability calculated from flat LCDM (WMAP7) with XCS selection function and Planck sensitivity; covariance of the cluster X-ray luminosity, temperature, and integrated comptonization parameter (?), as a function of cluster mass and redshift, as found in Millenium Gas Simulations. Also: characterize properties of the galaxy clusters in the final data release of XCS that are expected to be detected by Planck extended mission. Briefly discuss possible joint applications of the XCS and Planck data.
1109.1838
The pussling assembly of the MW halo -- contributions from dwarf Spheroidals and globular clusters
Koch, Lapine, A?l?kan
Classification of star clusters, low-luminosity galaxies, or tidal overdensities remain unclear for the MW satellites. Likewise, contribution to the build-up of the halo is still debated. Discuss current knowledge of stellar populations and chimo-dynamics in these faint satellites, with focus on dwarf spheroidal galaxies and the globular clusters in the outer Galacitic halo. Whether some of the outermost halo objects are dynamically associated with the MW halo at all is addressed, in terms of Leo I and II dwarf galaxies.
* I wish they could tell the conclusions...
1109.1846
Testing Einstein gravity with cosmic growth and expansion
Zhao, Li, Linder, Koyama, Bacon, Zhang
* Pade approximant: "best" approximation of a function by a rational function of given order. With this technique, the approximant's power series agrees with the power series of the function it is approximating. Often gives better approximation of the function than truncating its Taylor series. May still work where the Taylor series do not converge. Used extensively in computer calculations.
Test Einstein gravity using cosmological observations of both expansion and structure growth, with data from Union 2.1 (SNeIa), WMAP7 (CMB), CFHTLS (WL), and SDSS DR7 (z-space distortion). Fid modified gravity parameters of the generalized Poisson equations simultaneously with the effective equation of state ("w") for the BG evolution, exploring the covariances and model dependence. Results: GR is a good fit to the combined data. Using Pade approximant form for gravity deviations accurately captures the time and scale dependence for theories like f(R) and DGP gravity, weights high ad low redshift probes fairly.
1109.1888
Distribution function approach to redshift space distortions
Seljak, McDonald
Develop phase space distribution function approach to RSD: z-space density can be written as a sum over velocity moments of the distribution function. Moments are density weighted; the lowest orders are density, momentum density and stress-energy density. The series expansion is convergent on large scales. Expand velocity moments into helicity modes: Eigenmodes under rotation around the axis of Fourier mode direction; generalizes the scalar, vector, tensor decomposition of perturbations to an arbitrary order. Only equal helicity moments correlate; derive the angular dependence of the individual contributions to the redshift space power spectrum in terms of angle mu between k and LOS. Dominant term of mu^2 dependence on large scales is the X-correlation between the density and scalar part of momentum density, which can be related to the time derivative of the matter power spectrum. Additional terms contributing and dominating on small scales are the vector part of momentum density-momentum density correlations, the energy density-density correlations, and the scalar poart of anisotropic stress density-density correlations. Identify 7 terms contributing to mu^4 dependence. Some of the advantages of the distribution function approach are: the series expansion converges on large scales and remains valid in multi-stream situations. Brief discussion of implications for RSD in galaxies relative to DM, highlighting the issue of scale dependent bias of velocity moments correlators.
1109.1981
The complementarity of z-space distortions and the ISW effect
Shapiro, Crittenden, Percival
* RSD and ISW give orthogonal info
Assuming GR is correct on large-scales, RSDs and the ISW effect are both sensitive to the time derivative of the linear growth function. Investigate complementary or redundant information when combined to constrain evolution of the linear velocity power spectrum (f(z)/sigma8(z)), where f(z) is the logarithmic derivative of sigma8 wrt (1+z). Using 3d spherical harmonic expansion, compute covariance matricies of the signals for galaxy survey + CMB (Planck-like). Spherical harmonic basis allows accurate ISW estimates by avoiding the plane-parallel approximation (?); retains RSD information that is otherwise lost when projecting angular clustering onto redshift shells. Find correlation between ISW and RSD signals are low since the probes are sensitive to different modes. For default surveys, on large scales (k<0.05 Mpc/h) the ISW can improve constraints on f\sigma_8 by more than 10% compared to using RSD alone. In the future, when precision RSD measurements are available on smaller scales, the constraints from ISW will not be competitive, but will remain a useful consistency test for possible systematic contamination and alternative models of gravity.
* RSD and ISW both probe derivatives of linear growth; ISW sensitive to photons that come out of potential well (which might change shape over time) and is sensitive on large scales; RSD probes the peculiar velocity of galaxies falling into the potential well, and is sensitive on small scales.
1109.1821
The CFHTLS-Strong lensing legacy survey (SL2S): investigating the group-scale lenses with the SARCS sample
More, Cabanac, More, Alard, Limousin, Kneib, Gavazzi, Motta
Use of semi-automatic method to find gravitational arcs, visual inspection-pruned. 54 systems, 12 giant arcs, 2 radial arcs. Sytematic alignment of giant arcs with the ellipticity of the baryonic component of the lens. Lens redshift distribution of arcs (estimated from photometry) peaks at z~0.5. Largest lens sample probing group-scales for the first time. Compare observed image separation distribution with theoretical models: ISD accommodate models with both with and without adiabatic contraction (probably need more samples, yah?). (indeed,) Large sample might constrain relations such as the concentration-mass relation, mass-luminosity relation and slope of the luminosity function.
1109.1828
The XMM Cluster Survey: predicted overlap with the Planck Cluster Catalogue
Viana, da Silva, Ramos, Liddle, Lloyd-Davies, Romer, Kay, Collins, Hilton, Hosmer, Hoyle, Mehrtens, Miller, Sahlan, Stanford, Stott
Present serendipitously-discovered 15 clusters of galaxies in XCS that have high detection probability by Planck (3 of which already appear in the Planck Early SZ (ESZ) catalogue. Detection probability calculated from flat LCDM (WMAP7) with XCS selection function and Planck sensitivity; covariance of the cluster X-ray luminosity, temperature, and integrated comptonization parameter (?), as a function of cluster mass and redshift, as found in Millenium Gas Simulations. Also: characterize properties of the galaxy clusters in the final data release of XCS that are expected to be detected by Planck extended mission. Briefly discuss possible joint applications of the XCS and Planck data.
1109.1838
The pussling assembly of the MW halo -- contributions from dwarf Spheroidals and globular clusters
Koch, Lapine, A?l?kan
Classification of star clusters, low-luminosity galaxies, or tidal overdensities remain unclear for the MW satellites. Likewise, contribution to the build-up of the halo is still debated. Discuss current knowledge of stellar populations and chimo-dynamics in these faint satellites, with focus on dwarf spheroidal galaxies and the globular clusters in the outer Galacitic halo. Whether some of the outermost halo objects are dynamically associated with the MW halo at all is addressed, in terms of Leo I and II dwarf galaxies.
* I wish they could tell the conclusions...
1109.1846
Testing Einstein gravity with cosmic growth and expansion
Zhao, Li, Linder, Koyama, Bacon, Zhang
* Pade approximant: "best" approximation of a function by a rational function of given order. With this technique, the approximant's power series agrees with the power series of the function it is approximating. Often gives better approximation of the function than truncating its Taylor series. May still work where the Taylor series do not converge. Used extensively in computer calculations.
Test Einstein gravity using cosmological observations of both expansion and structure growth, with data from Union 2.1 (SNeIa), WMAP7 (CMB), CFHTLS (WL), and SDSS DR7 (z-space distortion). Fid modified gravity parameters of the generalized Poisson equations simultaneously with the effective equation of state ("w") for the BG evolution, exploring the covariances and model dependence. Results: GR is a good fit to the combined data. Using Pade approximant form for gravity deviations accurately captures the time and scale dependence for theories like f(R) and DGP gravity, weights high ad low redshift probes fairly.
1109.1888
Distribution function approach to redshift space distortions
Seljak, McDonald
Develop phase space distribution function approach to RSD: z-space density can be written as a sum over velocity moments of the distribution function. Moments are density weighted; the lowest orders are density, momentum density and stress-energy density. The series expansion is convergent on large scales. Expand velocity moments into helicity modes: Eigenmodes under rotation around the axis of Fourier mode direction; generalizes the scalar, vector, tensor decomposition of perturbations to an arbitrary order. Only equal helicity moments correlate; derive the angular dependence of the individual contributions to the redshift space power spectrum in terms of angle mu between k and LOS. Dominant term of mu^2 dependence on large scales is the X-correlation between the density and scalar part of momentum density, which can be related to the time derivative of the matter power spectrum. Additional terms contributing and dominating on small scales are the vector part of momentum density-momentum density correlations, the energy density-density correlations, and the scalar poart of anisotropic stress density-density correlations. Identify 7 terms contributing to mu^4 dependence. Some of the advantages of the distribution function approach are: the series expansion converges on large scales and remains valid in multi-stream situations. Brief discussion of implications for RSD in galaxies relative to DM, highlighting the issue of scale dependent bias of velocity moments correlators.
1109.1981
The complementarity of z-space distortions and the ISW effect
Shapiro, Crittenden, Percival
* RSD and ISW give orthogonal info
Assuming GR is correct on large-scales, RSDs and the ISW effect are both sensitive to the time derivative of the linear growth function. Investigate complementary or redundant information when combined to constrain evolution of the linear velocity power spectrum (f(z)/sigma8(z)), where f(z) is the logarithmic derivative of sigma8 wrt (1+z). Using 3d spherical harmonic expansion, compute covariance matricies of the signals for galaxy survey + CMB (Planck-like). Spherical harmonic basis allows accurate ISW estimates by avoiding the plane-parallel approximation (?); retains RSD information that is otherwise lost when projecting angular clustering onto redshift shells. Find correlation between ISW and RSD signals are low since the probes are sensitive to different modes. For default surveys, on large scales (k<0.05 Mpc/h) the ISW can improve constraints on f\sigma_8 by more than 10% compared to using RSD alone. In the future, when precision RSD measurements are available on smaller scales, the constraints from ISW will not be competitive, but will remain a useful consistency test for possible systematic contamination and alternative models of gravity.
* RSD and ISW both probe derivatives of linear growth; ISW sensitive to photons that come out of potential well (which might change shape over time) and is sensitive on large scales; RSD probes the peculiar velocity of galaxies falling into the potential well, and is sensitive on small scales.
Tuesday, September 13, 2011
Day 80
Tuesday. Farewell party for Phillip Bett and Karina last night. I'm putting in my best effort to find a great apartment, and I feel like I've more or less "caught up" with the web postings. Got a bank account, cell phone, making appointments for viewing.
Bonn Astronomisches Kolloquium
Stellar Spectroscopy unleashed -- ELTs and Red Supergiants in the Coma Cluster
Prof. Dr. Rolf Kudritzki
Chemical composition and distances to star forming galaxies are subject to large systematic uncertainties that are poorly understood. New method: use low resolution J-band spectroscopy of individual red supergiant stars (RSGs) in distance galaxies (Mauna Kea IRTF SpeX low resolution spectra of MW RSGs and MARCS model atmospheres). Individual metallicities and alpha/Fe ratio can be determined with an accuracy of about 0.1 dex. Extendable to MOSFIRE/Keck and KMOS/VLT. Can reach individual RSGs in galaxies as distant as the Coma Cluster in the next generation of ELTs and AO supported MOS instruments. Potential of observing integrated light of super star clusters (SSCs). The J-band light of these objects is entirely dominated by RSGs as soon as the cluster age is >8Myr. This allows for the determination of accurate detailed chemical composition by simple Pop Synth techniques. Since SSCs are bright in J, a large volume in the local universe can be studied this way.
* super star cluster: a very large region that is thought to be the precursor of a globular cluster. Typically contain very large number of young, massive stars that ionize a surrounding H II region, similar to the MW's Ultra dense H II regions (UDHIIs). SSC's H II regions is in trun surrounded by a cocoon of dust. The youngest SSCs are best observed in radio and infrared. n_e = 1e3 to 1e6 cm^-3.
Bonn Astronomisches Kolloquium
Stellar Spectroscopy unleashed -- ELTs and Red Supergiants in the Coma Cluster
Prof. Dr. Rolf Kudritzki
Chemical composition and distances to star forming galaxies are subject to large systematic uncertainties that are poorly understood. New method: use low resolution J-band spectroscopy of individual red supergiant stars (RSGs) in distance galaxies (Mauna Kea IRTF SpeX low resolution spectra of MW RSGs and MARCS model atmospheres). Individual metallicities and alpha/Fe ratio can be determined with an accuracy of about 0.1 dex. Extendable to MOSFIRE/Keck and KMOS/VLT. Can reach individual RSGs in galaxies as distant as the Coma Cluster in the next generation of ELTs and AO supported MOS instruments. Potential of observing integrated light of super star clusters (SSCs). The J-band light of these objects is entirely dominated by RSGs as soon as the cluster age is >8Myr. This allows for the determination of accurate detailed chemical composition by simple Pop Synth techniques. Since SSCs are bright in J, a large volume in the local universe can be studied this way.
* super star cluster: a very large region that is thought to be the precursor of a globular cluster. Typically contain very large number of young, massive stars that ionize a surrounding H II region, similar to the MW's Ultra dense H II regions (UDHIIs). SSC's H II regions is in trun surrounded by a cocoon of dust. The youngest SSCs are best observed in radio and infrared. n_e = 1e3 to 1e6 cm^-3.
Day 79
Sunday, rain & thunder. Yesterday was beautiful, walked along Rotweinwonderweg (all red-wine vineyards along the way), had Federweißer ("feather-white", refreshing, immature wine), was delicious.
1986ApJ...301...27B
Contraction of dark matter galactic halos dues to baryonic infall
Blumenthal, Faber, Flores, Primack
Some evidence (in 1986!) suggests that galaxies consist of roughly 10 percent baryonic matter by mass, and that baryons sink dissipatively by about a factor for 10 in radius during galaxy formation. Such infall strongly perturbs underlying dark matter distribution, pulling it inward and creating cores that are considerably smaller and denser than would have evolved without dissipation. Any discontinuity between the baryonic and dark matter mass distributions is smoothed out by the coupled motions of the two components. If dark halos have large core radii in the absence of dissipation, the infall scenario yields rotation curves that are flat over large distances, in agreement with observations of spiral galaxies. Such large dissipationless cores may result from large kinetic energy in protogalaxies at maximum expansion (?), perhaps as a result of subclustering, tidal effects, or anisotropic collapse.
* Early description of cluster core contraction (baryonic).
2002MNRAS.334..797S
Constraints on galaxy halo profiles from galaxy-galaxy lensing and Tully-Fisher/Fundamental Plane relations
Seljak
Observations of gg lensing from SDSS are combined with the TF and FP relations to derive constraints on galactic halo profiles. For both early- and late-type galaxies around L* the rotation velocity decreases significantly from its peak value at the optical radius to the virial radius r200 with vopt/v200 ~ 1.8. Such a decrease is expected in models in which the halo profile is very concentrated, so that it declines at steeper than the isothermal rate at large radii. This large decrease can be explained as a result of both a concentrated DM profile and a significant stellar contribution to the rotation velocity at the optical radii.
Model stellar component with a thin rotationally supported disc or Hernquist profile and use adiabatic DM response model to place limits on the halo concentration as a function of the stellar M/L ratio. For reasonable values of M/L, find concentration c200 consistent with CDM--no evidence for low concentrations for the majority of haloes in the Universe.
Discuss origin of the Faber-Jackson relation L~sigma^4 in light of the L~v200^5/2 relation found for early-type galaxies above L* from gg lensing. Decrease in vopt/v200 with luminosity above L*; at 7L* the ratio is 1.4. This is expected from the Fundamental plane relation: reduction in the baryonic contribution to the total mass at the optical radius, and a decrease n the optical to virial rotation velocity in the DM profile. Imply that relations such as TF and FJ are not simply those between the mass of the DM halo and the galaxy luminosity, but also significantly influenced by the baryonic effects on the rotation velocity at optical radii.
* Assuming a flat rotation curve (at optical radii and slightly outwards), what is the deviation at DM virial radius? This actually changes depending on the halo mass, apparently. The concentration affects the velocity ratio, which is consistent with LCDM (for reasonable values of M/L ratios).
1986ApJ...301...27B
Contraction of dark matter galactic halos dues to baryonic infall
Blumenthal, Faber, Flores, Primack
Some evidence (in 1986!) suggests that galaxies consist of roughly 10 percent baryonic matter by mass, and that baryons sink dissipatively by about a factor for 10 in radius during galaxy formation. Such infall strongly perturbs underlying dark matter distribution, pulling it inward and creating cores that are considerably smaller and denser than would have evolved without dissipation. Any discontinuity between the baryonic and dark matter mass distributions is smoothed out by the coupled motions of the two components. If dark halos have large core radii in the absence of dissipation, the infall scenario yields rotation curves that are flat over large distances, in agreement with observations of spiral galaxies. Such large dissipationless cores may result from large kinetic energy in protogalaxies at maximum expansion (?), perhaps as a result of subclustering, tidal effects, or anisotropic collapse.
* Early description of cluster core contraction (baryonic).
2002MNRAS.334..797S
Constraints on galaxy halo profiles from galaxy-galaxy lensing and Tully-Fisher/Fundamental Plane relations
Seljak
Observations of gg lensing from SDSS are combined with the TF and FP relations to derive constraints on galactic halo profiles. For both early- and late-type galaxies around L* the rotation velocity decreases significantly from its peak value at the optical radius to the virial radius r200 with vopt/v200 ~ 1.8. Such a decrease is expected in models in which the halo profile is very concentrated, so that it declines at steeper than the isothermal rate at large radii. This large decrease can be explained as a result of both a concentrated DM profile and a significant stellar contribution to the rotation velocity at the optical radii.
Model stellar component with a thin rotationally supported disc or Hernquist profile and use adiabatic DM response model to place limits on the halo concentration as a function of the stellar M/L ratio. For reasonable values of M/L, find concentration c200 consistent with CDM--no evidence for low concentrations for the majority of haloes in the Universe.
Discuss origin of the Faber-Jackson relation L~sigma^4 in light of the L~v200^5/2 relation found for early-type galaxies above L* from gg lensing. Decrease in vopt/v200 with luminosity above L*; at 7L* the ratio is 1.4. This is expected from the Fundamental plane relation: reduction in the baryonic contribution to the total mass at the optical radius, and a decrease n the optical to virial rotation velocity in the DM profile. Imply that relations such as TF and FJ are not simply those between the mass of the DM halo and the galaxy luminosity, but also significantly influenced by the baryonic effects on the rotation velocity at optical radii.
* Assuming a flat rotation curve (at optical radii and slightly outwards), what is the deviation at DM virial radius? This actually changes depending on the halo mass, apparently. The concentration affects the velocity ratio, which is consistent with LCDM (for reasonable values of M/L ratios).
Friday, September 9, 2011
Day 78
Friday (already?). Must read Reina's paper and comment--also check out the apartment that I want to rent in Poppelsdorf. And Nordstadt!
Bonn Astronomisches Kolloquium
The high time resolution universe survey and its jewels
Matthew Bailes (Swinburne University of Technology)
High Time Resolution Universe Survey: for pulsars and fast transients; a ambitious survey of the Southern sky with new digital spectrometers with fast read-out time; collaboration from Australia, Germany (MPIfR), Italy and the UK. Sister survey on the Northern sky at Effelsberg 100m. Complete survey 1PB of data, and possibly 600+ pulsars including millisecond pulsars, sources of single pulses of emission and systems useful for testing theories of relativistic gravity.
Describe hardware based on CASPER, data processing, new interference excision techniques, and the "Diamond Planet" pulse. GPU-based computers can search these data for accelerated pulsars in the near future, and maybe the first pulsar-black hole binary.
1109.0998
Testing general relativity on horizon scales and the primordial non-Gaussianity
Yoo, Hamaus, Seljak, Zaldarriaga
Test general relativity on horizon scales with proper GR description of the observed galaxy power spectrum (different from std Newtonian description). The GR effects classified as two new terms that represent the velocity and the gravitational potential, coupling time evolution of galaxy number density and Hubble parameter. Cf. density and velocity redshift-space distortion terms: former scales as H/k and correlates real and imaginary parts of Fourier modes; latter scales as (H/k)^2 where k is the comoving wave number and H is the conformal Hubble parameter. Use recently developed methods to reduce sampling variance and shot noise to show that in all sky galaxy redshift survey at low z the velocity term can be measured at 10-sigma if one can utilize halos of mass M>1e10 Msun, while the gravitational potential term itself can only be marginally detected. Demonstrate tha the GR effect is not degenerate with primordial non-Gaussian signature in galaxy bias--the ability to detect the primordial non-G is little compromised.
* neat! what is the detection significance if one can only use M>1e12 Msun galaxies?
1109.1033
Modeling techniques for measuring galaxy properties in multi-epoch surveys
Bosch
Thesis: advocate Bayesian approach to survey data reduction as a whole; focus specifically on the problem of modeling individual galaxies and stars. Present Monte Carlo algorithm that can efficiently sample from posterior probability for a flexible class of galaxy models; propose a method for constructing and convolving these models using Gauss-Hermite ("shapelet") functions. Designed to be efficient in multi-epoch modeling ("multifit"). Discuss how these methods are important for specific higher-level analysis, particularly WL, as well as their interaction with the many other aspects of a survey reduction pipeline.
* must read this, see if they test multifit...
1109.1121
Cosmology with Gravitational lensing
Heavens
Bonn Astronomisches Kolloquium
The high time resolution universe survey and its jewels
Matthew Bailes (Swinburne University of Technology)
High Time Resolution Universe Survey: for pulsars and fast transients; a ambitious survey of the Southern sky with new digital spectrometers with fast read-out time; collaboration from Australia, Germany (MPIfR), Italy and the UK. Sister survey on the Northern sky at Effelsberg 100m. Complete survey 1PB of data, and possibly 600+ pulsars including millisecond pulsars, sources of single pulses of emission and systems useful for testing theories of relativistic gravity.
Describe hardware based on CASPER, data processing, new interference excision techniques, and the "Diamond Planet" pulse. GPU-based computers can search these data for accelerated pulsars in the near future, and maybe the first pulsar-black hole binary.
1109.0998
Testing general relativity on horizon scales and the primordial non-Gaussianity
Yoo, Hamaus, Seljak, Zaldarriaga
Test general relativity on horizon scales with proper GR description of the observed galaxy power spectrum (different from std Newtonian description). The GR effects classified as two new terms that represent the velocity and the gravitational potential, coupling time evolution of galaxy number density and Hubble parameter. Cf. density and velocity redshift-space distortion terms: former scales as H/k and correlates real and imaginary parts of Fourier modes; latter scales as (H/k)^2 where k is the comoving wave number and H is the conformal Hubble parameter. Use recently developed methods to reduce sampling variance and shot noise to show that in all sky galaxy redshift survey at low z the velocity term can be measured at 10-sigma if one can utilize halos of mass M>1e10 Msun, while the gravitational potential term itself can only be marginally detected. Demonstrate tha the GR effect is not degenerate with primordial non-Gaussian signature in galaxy bias--the ability to detect the primordial non-G is little compromised.
* neat! what is the detection significance if one can only use M>1e12 Msun galaxies?
1109.1033
Modeling techniques for measuring galaxy properties in multi-epoch surveys
Bosch
Thesis: advocate Bayesian approach to survey data reduction as a whole; focus specifically on the problem of modeling individual galaxies and stars. Present Monte Carlo algorithm that can efficiently sample from posterior probability for a flexible class of galaxy models; propose a method for constructing and convolving these models using Gauss-Hermite ("shapelet") functions. Designed to be efficient in multi-epoch modeling ("multifit"). Discuss how these methods are important for specific higher-level analysis, particularly WL, as well as their interaction with the many other aspects of a survey reduction pipeline.
* must read this, see if they test multifit...
1109.1121
Cosmology with Gravitational lensing
Heavens
Thursday, September 8, 2011
Day 77
Thursday. Went to pick up the Jobticket.
Bonn Master-Kolloquium
Constraints on the "Universal" pressure profile through the SZ power spectrum
Miriam Elizabeth Ramos Ceja
Power spectrum of tSZ effect: success for cosmology depends on the understanding of the gas physics in galaxy clusters. Discuss impact of modifications to the "universal" gas pressure profile on tSZ power spectrum. Compare with CMB observations. The universal pressure profile gives excess of tSZ power when compared to SPT observations. Modification toe the pressure profile can give compatible results with SPT measurements.
Bonn Master-Kolloquium
Constraints on the "Universal" pressure profile through the SZ power spectrum
Miriam Elizabeth Ramos Ceja
Power spectrum of tSZ effect: success for cosmology depends on the understanding of the gas physics in galaxy clusters. Discuss impact of modifications to the "universal" gas pressure profile on tSZ power spectrum. Compare with CMB observations. The universal pressure profile gives excess of tSZ power when compared to SPT observations. Modification toe the pressure profile can give compatible results with SPT measurements.
Tuesday, September 6, 2011
Day 76
Wednesday. Gotta push the a2218 through the pipeline, and copy data and code to my laptop today.
UCB Astro Theory Lunch
Galaxy kinematics and DM halos with VIRUS-P
Jeremy Murphy (UT Austin)
Elliptical galaxies: process of galaxy formation and evolution takes place in the centers of DM halos. Observational methods: estimate the mass and radial extent of these halos. Extended stellar halos of M87 and M49 in the Virgo cluster discussed; show if they agree with other (DM) mass tracers.
1109.0285
MOKA: a new tool for Strong Lensing Studies
Giocoli, Meneghetti, Bartelmann, Moscardini, Boldrin
* compare with Gravlens
New algorithm for simulating gravitational lensing signal from cluster-sized halos (NFW profile, concentration decreasing with mass, large amount of substructures). Create realistic lenses based on numerical simulations with properties independent of numerical resolution. Perform systematic studies of strong lensing cross section in dependence of halo structure; find dependence on concentration and the inner slope of density profile of a halo; then halo triaxiality and the presence of a BCG.
* can this be used to look at data? no, it seems like it's just a calculation based on simulation...
1109.0529
Neutral Hydrogen Tully Fisher Relation: The case for Newtonian Gravity
Chakraborti, Khedekar
TF relation: intrinsic luminosities related to rotation velocities of disk galaxies. Baryonic TF relation explained by both DM+Newtonian and MOND. But BTF relation ignores contribution from hot gas and oversimplifies galaxy-scale physics. Advocate use of Hydrogen TF (HITF), free of dust obscuration and stellar evolution effects. Incorporate physics of hot gas from SNe feedback, which drives porosity of the ISM. Simple model with SNe feedback generalized to include parameterized effective gravitational force law. Kennicutt-Schmidt (KS) law for star formation and simple Newtonian gravity adequate for explaining observed HI scaling relations. Data rules out MOND-like theories in this model.
* How does the model rule out MOND??
1109.0548
Substructure in the lens HE 0435-1223
Fadely, Keeton
Investigate properties of DM substructure for HE 0435 (z_l=0.455) through its effects on the positions and flux ratios of the quadruply-imaged BG quasar (z_s=1.689). Examine individual substructure placement, and a full population of substructure assuming clump masses follow a mass function dN/dM~M^-1.9.
1109.0549
An enhanced cosmological Li6 abundance as a potential signature of residual dark matter annihilations
Ellis, Fields, Luo, Olive, Spanos
Constrained minimal supersymmetric extension of the standard model (CMSSM) with late-time DM annihilations (after BBN) can affect primordial element abundance: not much with He3, He4 and Li7, but Li6 is enhanced, but given LHC constraints, not by much. Similar enhancement can also be given for non-universal Higgs mass (NUHM1) models.
* Li7 is low compared to BBN predictions, unclear if due to astrophysics. Li6 is also lower observed.
1109.0850
Galaxy cluster searches based on photometric redshifts of the four CFHTLS wide fields
Durret, Adami, Cappi, Maurogordato, Marquez, Ilbert, Coupon, Arnouts, ...Le Fevre, ...McCracken, Mellier, ... etal
Developed a method for detecting clusters in large imaging surveys: based on structures in slices of photometric redshifts. Detection rate validity estimated by applying method to Millennium simulation. Detect 4061 candidate clusters at >3 sigma (6k for >2sigma) in 0.1<z<1.15. Estimated mean masses of 1.3e14 and 1.3e15 M_sun. Catalog available via VizieR online. Check cluster characteristics (color-mag relation, luminosity function); cluster-cluster correlation function compared to other reports; analyze large scale filamentary galaxy distributions.
1109.0873
Model-independent reconstruction of the expansion history of the universe from SNe Ia
Benitez-Herrera, Roepke, Hillebrandt, Mignone, Bartelmann, Weller
Model-independent reconstruction of the expansion history based on Union2 sample. Tests geometry of the universe without any assumptions made on the energy content. Better suited to constrain DE and non-standard cosmological models. Can also be used for pointing out systematic errors in SNe data, and planning future SNe Ia cosmology campaigns.
* How do they do this??
1109.0953
ACT: ACT-CL J0102-4215 "El Gordo", a massive merging cluster at z=0.87
Menanteau, Hughes, Sifon, Hilton, Gonzalez... Das, Devlin, ... Marsden, ... Page, Reese, Sehgal, ... Spergel ... et al.
Most likely the most massive, hottest, most X-ray luminous and brightest SZ effect cluster known at z>0.6. Discovered in the ACT SZ survey of 755 sq. degrees. 89 members have spectra with cluster redshift of 0.870; sigma_v = 1321 km/s. Chandra: Tx=14.5 keV, Lx=2e45 erg/s (at 0.5-2.0 keV band). Cluster mass estimates: M_200=2e15M_sun. Optical and Chandra data show evidence of major merger (2:1). Shows temperature variations from 6.6 keV (cool core) to 22 keV. Wake in X-ray surface brightness; estimate merger speed of around 1300 km/s with assumed merger timescale of 1Gyr. Rare massive cluster, but allowed in LCDM; but unlikely to be reproduced in N-body sims.
Bonn MPIfR Lunch Colloquium
IRAS 16293-2422: a very young FU Orionis analog entering a phase of enhanced accretion?
Laurent Loinaird (MPIfR Bonn/UNAM Mexico)
IRAS 16293 underwent (possibly one-sided) ejection in 2011, after 40% increase in accretion rate. Unambiguous evidence of the direct coupling (presumably magnetic) between accretion and ejection processes during the earliest stages of stellar evolution. Validates claims of accretion history reconstruction of young stellar objects from fossil record of ejection imprinted on their outflow systems. Excess accretion approximately 3x the ejection mass, in good agreement with theory. Since 1980s, only the 2006 and 2011 events are recorded ejection events.
Bonn Promotions-Kolloquium
Study of two radio gravitational lenses: insight into the high-redshift universe and properties of mass distribution
Filomena Volino
Astrophysical applications of GL, concentrate on lensing as tool to study the intervening mass distribution in the lens system MG J0414+0534. Results of VLBI at 1.7GHz and lens modeling results, full set of constraints from observations.
* I have to hear about the intervening mass distribution.
* three talks today, and a Skype con.
Bonn MPIfR Special Colloquium
A multiwavelength view of the microquasar Cyg X-1: spectral variability, Gamma-ray polarization, and jets
Victoria Grinberg (Remeis Observatory & ECAP)
Cyg X-1: discovered in 1965, persistent high mass X-ray binary of O supergiant + stellar mass BH; i.e., a down-scaled versions of AGN, supported by observations of radio jets. Shows distinct X-ray states (spectral and timing properties), and correlated radio behaviour. Campaign of X-ray and gamma-ray observations has goal to understand the inflow/outflow connection for BHs on all mass-scales. Shows Gamma-ray polarization of an X-ray binary; emission component is produced in jets.
Bonn MPIfR Special Colloquium
Astrometry Lost and Regained: from a modest experiment in Copenhagen in 1925 to the Hipparcos and Gaia space missions
Erik Hoeg (Niels Bohr Institute)
Astrometry! Important for celestial phenomena, control of telescopes and satellites, and monitoring Earth's rotation. Hipparcos made astrometry flourish, soon to be followed by Gaia mission. Hipparcos in 1980: one star detected at a time (photoelectric detectors); Roemer mission in 1992: CCD detectors (10k stars simultaneous), rotating satellite, systematic scan. Gaia in 1993-1997: interferometric option (but direct imaging of CCDs was considered to be better, and was used for SGaia mission).
1107.1378
Estimate of halo ellipticity as a function of radius with flexions
Xinzhong Er, Mao, Xu, Cao
Triaxial DM halos: radial distribution of halo ellipticity depends on baryonic processes and the nature of DM particles. Use lensing flexion ratios to measure halo ellipticity as a function of radius. Use weight function, study relationship between first and second order statistics of flexion ratios (?), use both the reduce bias in ellipticity estimation. Perform numerical tests and demonstrate bias reduction. Minimum mean flexion ratio can be used to trace the centers of galaxy clusters.
UCB Astro Theory Lunch
Galaxy kinematics and DM halos with VIRUS-P
Jeremy Murphy (UT Austin)
Elliptical galaxies: process of galaxy formation and evolution takes place in the centers of DM halos. Observational methods: estimate the mass and radial extent of these halos. Extended stellar halos of M87 and M49 in the Virgo cluster discussed; show if they agree with other (DM) mass tracers.
1109.0285
MOKA: a new tool for Strong Lensing Studies
Giocoli, Meneghetti, Bartelmann, Moscardini, Boldrin
* compare with Gravlens
New algorithm for simulating gravitational lensing signal from cluster-sized halos (NFW profile, concentration decreasing with mass, large amount of substructures). Create realistic lenses based on numerical simulations with properties independent of numerical resolution. Perform systematic studies of strong lensing cross section in dependence of halo structure; find dependence on concentration and the inner slope of density profile of a halo; then halo triaxiality and the presence of a BCG.
* can this be used to look at data? no, it seems like it's just a calculation based on simulation...
1109.0529
Neutral Hydrogen Tully Fisher Relation: The case for Newtonian Gravity
Chakraborti, Khedekar
TF relation: intrinsic luminosities related to rotation velocities of disk galaxies. Baryonic TF relation explained by both DM+Newtonian and MOND. But BTF relation ignores contribution from hot gas and oversimplifies galaxy-scale physics. Advocate use of Hydrogen TF (HITF), free of dust obscuration and stellar evolution effects. Incorporate physics of hot gas from SNe feedback, which drives porosity of the ISM. Simple model with SNe feedback generalized to include parameterized effective gravitational force law. Kennicutt-Schmidt (KS) law for star formation and simple Newtonian gravity adequate for explaining observed HI scaling relations. Data rules out MOND-like theories in this model.
* How does the model rule out MOND??
1109.0548
Substructure in the lens HE 0435-1223
Fadely, Keeton
Investigate properties of DM substructure for HE 0435 (z_l=0.455) through its effects on the positions and flux ratios of the quadruply-imaged BG quasar (z_s=1.689). Examine individual substructure placement, and a full population of substructure assuming clump masses follow a mass function dN/dM~M^-1.9.
1109.0549
An enhanced cosmological Li6 abundance as a potential signature of residual dark matter annihilations
Ellis, Fields, Luo, Olive, Spanos
Constrained minimal supersymmetric extension of the standard model (CMSSM) with late-time DM annihilations (after BBN) can affect primordial element abundance: not much with He3, He4 and Li7, but Li6 is enhanced, but given LHC constraints, not by much. Similar enhancement can also be given for non-universal Higgs mass (NUHM1) models.
* Li7 is low compared to BBN predictions, unclear if due to astrophysics. Li6 is also lower observed.
1109.0850
Galaxy cluster searches based on photometric redshifts of the four CFHTLS wide fields
Durret, Adami, Cappi, Maurogordato, Marquez, Ilbert, Coupon, Arnouts, ...Le Fevre, ...McCracken, Mellier, ... etal
Developed a method for detecting clusters in large imaging surveys: based on structures in slices of photometric redshifts. Detection rate validity estimated by applying method to Millennium simulation. Detect 4061 candidate clusters at >3 sigma (6k for >2sigma) in 0.1<z<1.15. Estimated mean masses of 1.3e14 and 1.3e15 M_sun. Catalog available via VizieR online. Check cluster characteristics (color-mag relation, luminosity function); cluster-cluster correlation function compared to other reports; analyze large scale filamentary galaxy distributions.
1109.0873
Model-independent reconstruction of the expansion history of the universe from SNe Ia
Benitez-Herrera, Roepke, Hillebrandt, Mignone, Bartelmann, Weller
Model-independent reconstruction of the expansion history based on Union2 sample. Tests geometry of the universe without any assumptions made on the energy content. Better suited to constrain DE and non-standard cosmological models. Can also be used for pointing out systematic errors in SNe data, and planning future SNe Ia cosmology campaigns.
* How do they do this??
1109.0953
ACT: ACT-CL J0102-4215 "El Gordo", a massive merging cluster at z=0.87
Menanteau, Hughes, Sifon, Hilton, Gonzalez... Das, Devlin, ... Marsden, ... Page, Reese, Sehgal, ... Spergel ... et al.
Most likely the most massive, hottest, most X-ray luminous and brightest SZ effect cluster known at z>0.6. Discovered in the ACT SZ survey of 755 sq. degrees. 89 members have spectra with cluster redshift of 0.870; sigma_v = 1321 km/s. Chandra: Tx=14.5 keV, Lx=2e45 erg/s (at 0.5-2.0 keV band). Cluster mass estimates: M_200=2e15M_sun. Optical and Chandra data show evidence of major merger (2:1). Shows temperature variations from 6.6 keV (cool core) to 22 keV. Wake in X-ray surface brightness; estimate merger speed of around 1300 km/s with assumed merger timescale of 1Gyr. Rare massive cluster, but allowed in LCDM; but unlikely to be reproduced in N-body sims.
Bonn MPIfR Lunch Colloquium
IRAS 16293-2422: a very young FU Orionis analog entering a phase of enhanced accretion?
Laurent Loinaird (MPIfR Bonn/UNAM Mexico)
IRAS 16293 underwent (possibly one-sided) ejection in 2011, after 40% increase in accretion rate. Unambiguous evidence of the direct coupling (presumably magnetic) between accretion and ejection processes during the earliest stages of stellar evolution. Validates claims of accretion history reconstruction of young stellar objects from fossil record of ejection imprinted on their outflow systems. Excess accretion approximately 3x the ejection mass, in good agreement with theory. Since 1980s, only the 2006 and 2011 events are recorded ejection events.
Bonn Promotions-Kolloquium
Study of two radio gravitational lenses: insight into the high-redshift universe and properties of mass distribution
Filomena Volino
Astrophysical applications of GL, concentrate on lensing as tool to study the intervening mass distribution in the lens system MG J0414+0534. Results of VLBI at 1.7GHz and lens modeling results, full set of constraints from observations.
* I have to hear about the intervening mass distribution.
* three talks today, and a Skype con.
Bonn MPIfR Special Colloquium
A multiwavelength view of the microquasar Cyg X-1: spectral variability, Gamma-ray polarization, and jets
Victoria Grinberg (Remeis Observatory & ECAP)
Cyg X-1: discovered in 1965, persistent high mass X-ray binary of O supergiant + stellar mass BH; i.e., a down-scaled versions of AGN, supported by observations of radio jets. Shows distinct X-ray states (spectral and timing properties), and correlated radio behaviour. Campaign of X-ray and gamma-ray observations has goal to understand the inflow/outflow connection for BHs on all mass-scales. Shows Gamma-ray polarization of an X-ray binary; emission component is produced in jets.
Bonn MPIfR Special Colloquium
Astrometry Lost and Regained: from a modest experiment in Copenhagen in 1925 to the Hipparcos and Gaia space missions
Erik Hoeg (Niels Bohr Institute)
Astrometry! Important for celestial phenomena, control of telescopes and satellites, and monitoring Earth's rotation. Hipparcos made astrometry flourish, soon to be followed by Gaia mission. Hipparcos in 1980: one star detected at a time (photoelectric detectors); Roemer mission in 1992: CCD detectors (10k stars simultaneous), rotating satellite, systematic scan. Gaia in 1993-1997: interferometric option (but direct imaging of CCDs was considered to be better, and was used for SGaia mission).
1107.1378
Estimate of halo ellipticity as a function of radius with flexions
Xinzhong Er, Mao, Xu, Cao
Triaxial DM halos: radial distribution of halo ellipticity depends on baryonic processes and the nature of DM particles. Use lensing flexion ratios to measure halo ellipticity as a function of radius. Use weight function, study relationship between first and second order statistics of flexion ratios (?), use both the reduce bias in ellipticity estimation. Perform numerical tests and demonstrate bias reduction. Minimum mean flexion ratio can be used to trace the centers of galaxy clusters.
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