Wednesday. Dinner at Laura & Robert's tonight.
UCB CDI Seminar
Transfer and active learning in astronomical datasets
Ricardo Vilalta
Machine learning in astronomy: (1) "transfer learning" -- exploit the existence of a data model from a similar (but not exactly the same) domain of application to the new domain. (2) "active learning" -- dynamically select only those instances of the new domain most informative for prediction. Both paradigm can greatly enhance the predictive accuracy and efficiency of learning. Application: automatic geomorphic mapping of planet Mars. Also: variable star classification, galaxy classification, etc.
1108.5384
The impact of baryon physics on the structure of high-redshift galaxies
Zemp, Gnedin, Gnedin, Kravtsov
Study the structure of galaxies at z>2 using cosmo simulations with improved modeling of the ISM and star formation. Stellar distribution is compact because H_2 (where stars form) is more concentrated towards the center of galaxies than atomic H. For halos above 1e11 M_sun, the median half-mass radius of stellar disks is 0.8 kpc at z=3. Vertical structure of molecular disk is much thinner than that of the atomic neutral gas (why?). When radiative transfer included (molecular dynamics, I presume), the DM halo change shape from prolate to mildly oblate (affected by baryon disk?) , but no evidence of a significant DM disk around stellar disk. Outer halo regions retain orientation acquired during accretion and mergers, and are significantly misaligned with the inner regions. Radial profile of DM halos contracts in response to baryon dissipation, and establish an approximately isothermal profile throughout most of the halo (!). Effect accurately described by a modified model of "halo contraction". The angular momentum of a fixed amount of inner dark matter is approximately conserved over time (?), compared to the dissipationless case where most of it is transferred outward during mergers. Conservation of the dark matter angular momentum provides supporting evidence for the validity of the halo contraction model in hierarchical galaxy formation processes.
* pretty interesting. Does it simulate disk/elliptical/dwarf galaxies well?
* supports halo contraction due to baryonic dissipation.
LBL INPA
Distribution function approach to redshift space distortions: N-body simulations
Teppei Okumura
Galaxy redshift surveys: redshift space distortions directly probe the cosmic growth history of density perturbations. A distribution function approach: RSD written as sum over density-weighted velocity moment correlators. From N-body simulation, this particular approach show that this formalism predicts the true power spectrum up to sufficiently small scales. Can also be used for biased objects, such as DM halos and galaxies.
UCB SSL Colloquium
3D simulations of solar surface: from limb to secular models
Laurent Piau
* Kepler mission: A search for habitable planets orbiting other stars, using light curves. Launched 2009, planned mission lifetime of at least 3.5 years.
* Johannes Kepler: German mathematician, astronomer and astrologer, b.1571 d.1630. Assistant to Tycho Brahe.
Wednesday, August 31, 2011
Tuesday, August 30, 2011
Day 71
Tuesday. Lucas' PhD celebration bash was last night. Might still be hung over.
1108.5176
Simulatios of early baryonic structure formation with stream velocity: I. Halo abundance
Naoz, Yoshida, Gnedin
Relative velocity between the DM and baryons (v_bc) at the time of recombination can affect the structure formation in the early universe (Tseliakhovich+Hirata 2010). Statistically quantify using large cosmological simulations: separate transfer functions for baryons and dark matter; three different high resolution sets of simulations that vary the value of relative velocity. The total number of halos suppressed by 20% at z=25 for vbc = 1 sigma(vbc) and 50% for vbc = 3.4 sigma (vbc), remaining above 30% to z=11. High abundance of "empty halos" (halos with half the gas fraction of cosmic mean) found: for vbc = 1sigma(vbc), all new halos below 1e5Msun are empty at z=19. The high abundance of empty halos results in significant delay in the formation of gas rich mini-halos and the first galaxies.
1108.5282
Rating growth of scientific knowledge and risk from theory bubbles
Loeb
Advocate the need for a website operated by graduate students that will use various measures of publicly available data (e.g., growth rate of research grants, publications, faculty jobs) to gauge the future dividends of various research frontiers. Analysis can benefit from past experience; aim to alert the community of the risk from future theory bubbles.
1108.5211
Experimental test of airplane boarding methods
Steffen, Hotchkiss
Report experimental comparison of different airplane boarding methods. 757 mock with 12 rows of 6 seats and a single aisle; 5 methods with 72 passengers of various ages; significan reduction of boarding time found in optimized methods over traditional methods.
1108.2506
Only marginal alignment of disc galaxies
Andrae, Jahnke
Angular-momentum acquisition of rotationally supported disc galaxies: key to understand formation of this type of galaxies. Tidal-torque theory: tries to explain the angular momentum acquisition in a cosmological framework, predicts positive autocorrelations of angular-momentum orientation and spiral-arm handedness on distances of 1Mpc/h. Disc alignment also an IA contamination to WL signal. Explain how to propagate the important errors (redshift, ellipticity, morphological classifications). From SDSS, positive autocorrelations of spiral-arm handedness and angular momentum orientations on distances of 1Mpc/h are plausible but not statistically significant. (Local Group shows not evidence of alignment either.) Ellipticity estimates based on second moments are strongly biased by galactic bulges, corrupts correlation estimates. Overestimates the impact of disc alignment on WL studies. Discuss the potential of future sky surveys--PanSTARRS and LSST cannot be used for photoz (to measure...?)
* IA is marginal for disc galaxies. Bulge may produce some correlation signals.
* I want to understand what alignment they're talking about--it doesn't seem like they're talking about alignment to LSS, but rather the angular momentum of the galaxy to the spiral arm structure...
1108.2635
The WIggleZ Dark Energy Survey: mapping the distance-redshift relation with BAO
Blake, Kazin, etal
BAO measurements at z=0.44, 0.6, 0.73 with WiggleZ. Combine with 6dFGS and SDSS, BAO significance of 4.9 sigma. Fit cosmological models with 6 distance-redshift data points; compare results to SNe and CMB data. BAO and SNe produce consistent measurements of w of DE. Provides check for systematic errors in either of these distance probes when combined separately with CMB (?). Combining all, find w=-1.03 pm 0.08 for a flat universe. Assume w=-1, find Omega_k = -0.004 pm 0.006.
1108.2637
The WiggleZ DE survey: measuring the cosmic expansion history using the Alcock-Paczynski test and distant SNe
Blake, Glazebrook, et al
Combine distant SNe observations with geometrical analysis of galaxy clustering within the WiggleZ DE survey; using the AP test to measure the distortion of standard spheres. Constitutes a robust and non-parametric measurement of the Hubble expansion rate as a fn of time with 4 bins in 0.1<z<0.9. Demonstrate that cosmic expansion is accelerating, in a manner independent of the parameterization of the cosmological model (although assuming cosmic homogeneity). Expansion history is consistent with a w=-1.
* how do they use the AP test to determine Hubble rate?
1108.2657
Measuring large-scale structure with quasars in narrow-band filter surveys
Abramo, Strauss, Lima, Hernandez-Monteagudo, Lazkoz, Moles, de Oliveira, Sendra, Sodra
Show that large-area imaging survey using narrow-band filters can detect quasars in sufficiently high number densities to turn them into suitable tracers of large-scale structure. Narrow-band optical survey that can detect to i=23 could reach volumetric number densities as high as 1e-4 h^3 Mpc^-3 (comoving) at z~1.5, leading to precision measurements of the power spectrum up to z~3-4. Possible to employ quasars to measure BAO at high z, where the uncertainties from z distortions and nonlinearities are much (?) smaller than at z<1. Study the future impact of J-PAS: narrowband (100A fwhm) 42 filter survey of 1/5 of unobscured sky. Due to broad emission line, get excellent photo-z of sigma_z = 0.002(1+z).
1108.2700
It was twenty years ago today...
Ginsparg
20th anniversary of hep-th@xxx.lanl.gov (now arXiv.org). Trace some historical context and early developement of the resousrce, its later trajectory; close with thoughts about future.
1108.5176
Simulatios of early baryonic structure formation with stream velocity: I. Halo abundance
Naoz, Yoshida, Gnedin
Relative velocity between the DM and baryons (v_bc) at the time of recombination can affect the structure formation in the early universe (Tseliakhovich+Hirata 2010). Statistically quantify using large cosmological simulations: separate transfer functions for baryons and dark matter; three different high resolution sets of simulations that vary the value of relative velocity. The total number of halos suppressed by 20% at z=25 for vbc = 1 sigma(vbc) and 50% for vbc = 3.4 sigma (vbc), remaining above 30% to z=11. High abundance of "empty halos" (halos with half the gas fraction of cosmic mean) found: for vbc = 1sigma(vbc), all new halos below 1e5Msun are empty at z=19. The high abundance of empty halos results in significant delay in the formation of gas rich mini-halos and the first galaxies.
1108.5282
Rating growth of scientific knowledge and risk from theory bubbles
Loeb
Advocate the need for a website operated by graduate students that will use various measures of publicly available data (e.g., growth rate of research grants, publications, faculty jobs) to gauge the future dividends of various research frontiers. Analysis can benefit from past experience; aim to alert the community of the risk from future theory bubbles.
1108.5211
Experimental test of airplane boarding methods
Steffen, Hotchkiss
Report experimental comparison of different airplane boarding methods. 757 mock with 12 rows of 6 seats and a single aisle; 5 methods with 72 passengers of various ages; significan reduction of boarding time found in optimized methods over traditional methods.
1108.2506
Only marginal alignment of disc galaxies
Andrae, Jahnke
Angular-momentum acquisition of rotationally supported disc galaxies: key to understand formation of this type of galaxies. Tidal-torque theory: tries to explain the angular momentum acquisition in a cosmological framework, predicts positive autocorrelations of angular-momentum orientation and spiral-arm handedness on distances of 1Mpc/h. Disc alignment also an IA contamination to WL signal. Explain how to propagate the important errors (redshift, ellipticity, morphological classifications). From SDSS, positive autocorrelations of spiral-arm handedness and angular momentum orientations on distances of 1Mpc/h are plausible but not statistically significant. (Local Group shows not evidence of alignment either.) Ellipticity estimates based on second moments are strongly biased by galactic bulges, corrupts correlation estimates. Overestimates the impact of disc alignment on WL studies. Discuss the potential of future sky surveys--PanSTARRS and LSST cannot be used for photoz (to measure...?)
* IA is marginal for disc galaxies. Bulge may produce some correlation signals.
* I want to understand what alignment they're talking about--it doesn't seem like they're talking about alignment to LSS, but rather the angular momentum of the galaxy to the spiral arm structure...
1108.2635
The WIggleZ Dark Energy Survey: mapping the distance-redshift relation with BAO
Blake, Kazin, etal
BAO measurements at z=0.44, 0.6, 0.73 with WiggleZ. Combine with 6dFGS and SDSS, BAO significance of 4.9 sigma. Fit cosmological models with 6 distance-redshift data points; compare results to SNe and CMB data. BAO and SNe produce consistent measurements of w of DE. Provides check for systematic errors in either of these distance probes when combined separately with CMB (?). Combining all, find w=-1.03 pm 0.08 for a flat universe. Assume w=-1, find Omega_k = -0.004 pm 0.006.
1108.2637
The WiggleZ DE survey: measuring the cosmic expansion history using the Alcock-Paczynski test and distant SNe
Blake, Glazebrook, et al
Combine distant SNe observations with geometrical analysis of galaxy clustering within the WiggleZ DE survey; using the AP test to measure the distortion of standard spheres. Constitutes a robust and non-parametric measurement of the Hubble expansion rate as a fn of time with 4 bins in 0.1<z<0.9. Demonstrate that cosmic expansion is accelerating, in a manner independent of the parameterization of the cosmological model (although assuming cosmic homogeneity). Expansion history is consistent with a w=-1.
* how do they use the AP test to determine Hubble rate?
1108.2657
Measuring large-scale structure with quasars in narrow-band filter surveys
Abramo, Strauss, Lima, Hernandez-Monteagudo, Lazkoz, Moles, de Oliveira, Sendra, Sodra
Show that large-area imaging survey using narrow-band filters can detect quasars in sufficiently high number densities to turn them into suitable tracers of large-scale structure. Narrow-band optical survey that can detect to i=23 could reach volumetric number densities as high as 1e-4 h^3 Mpc^-3 (comoving) at z~1.5, leading to precision measurements of the power spectrum up to z~3-4. Possible to employ quasars to measure BAO at high z, where the uncertainties from z distortions and nonlinearities are much (?) smaller than at z<1. Study the future impact of J-PAS: narrowband (100A fwhm) 42 filter survey of 1/5 of unobscured sky. Due to broad emission line, get excellent photo-z of sigma_z = 0.002(1+z).
1108.2700
It was twenty years ago today...
Ginsparg
20th anniversary of hep-th@xxx.lanl.gov (now arXiv.org). Trace some historical context and early developement of the resousrce, its later trajectory; close with thoughts about future.
Sunday, August 28, 2011
Day 70
Monday. Start of my new academic life in Europe.
UCB Astro seminar
From theoretical promise to observational reality: calibration and foreground subtraction in 21cm tomography
Adrian Liu (MIT)
* What are the fundamental physics that 21cm can probe?
21cm maps distribution of neutral hydrogen using the redshifted hyperfine transition. 21cm tomography has the potential to probe epoch of reionization, the preceding Dark Ages, and fundamental physics at unprecedented levels of accuracy. Expected signal is of the order of 10mK, where the foregrounds are expected to be 100 to 1000K. 21cm requires exquisitely well-calibrated radio interferometer array, as well as data processing algorithms that are capable of high precision foreground subtraction. Discuss existing proposals for 21cm calibration and FG subtraction; differences between 21cm tomography and traditional radio astronomy, CMB or galaxy surveys. Redundant calibration, principal component models or FG spectra, and systematic, unbiased framework for FG subtraction necessary.
Saturday, August 27, 2011
Day 69
Saturday. No, wait, Sunday. I slept away Saturday. It's 2am now in Zürich.
UCB TAC seminar
3D simulations of solar surface: from limb to secular models
Laurent Piau (CEA-Saclay)
Stagger code: simulates 3D radiation hydrodynamics and magnetic field at the solar surface; addresses ionization effects, compressibility, solves equations of radiation transfer and induction. Solar model atmospheres computed with OPAL EoS using the most recent solar composition (?). Models account for the magnetic field. Offer means of interpreting observations of space borne missions dedicated to solar surface dynamics. Discuss impact of magnetism on limb darkening profile. Effects of surface convection = "the surface term" in helio- and astroseismology; it must be understood well, and that can be done through modeling.
1108.4905
The lensing properties of the Einasto profile
Retana-Montenegro, Frutos-Alfaro
* Einasto profile: describes 3d profile rho(r) ~ exp(-Ar^alpha)
* NFW profile: descries 3d profile
* Sersic profile: describes surface brightness (projected density)
Derives surface mass density, deflection angle, lens equation, deflection potential, magnification, shear and critical curves of Einasto profile, which is hard because it is non-analytic for general values of the Einasto index.
1108.4688
The impact of massive neutrinos on the abundance of massive clusters
Ichiki, Takada
Spherical top-hat collapse model for a mixed DM model that includes neutrinos of mass 0.05 to 0.1 eV. Take into account relative differences between the density perturbation amplitudes of radiation, baryon, CDM and neutrinos around the top-hat CDM overdensity, assuming adiabatic initial conditions. Also solve Boltzmann hierarchy equations to obtain time evolution of neutrino perturbations, including late-time NL gravitational potential. Presence of massive neutrion slows down the collapse of CDM overdensity: neutrinos cannot fully catch up with the NL CDM perturbation due to its large free-streaming velocity for the ranges of neutrino masses and halo masses considered. The CDM overdensity collapse time is well monitored by the linear-theory extrapolated overdensity, smoothed for a given halo mass scale, taking into account the suppression effect of the massive neutrinos on the linear growth rate. Presence of massive neutrinos of 0.05-0.1 eV cause significant decrease in the abundance of massive halos compared to model without the massive neutrinos: 25% for 1e15 Msun, or factor 2 for z=1.
1108.4864
Vesto Slipher and the First Galaxy Redshifts
Thompson
Hubble claimed credit of other astronomers (e.g., Slipher, Lemaitre, Humason...).
1108.4929
Cluster-Cluster lensing and the case of Abell 383
Zitrin, Rephaeli, Sadeh, Medezinski, Umetsu, Sayers, Nonino, Morandi, Molino, Czakon, Golwala
Assess the likelihood of cluster-cluster lensing (CCL). Describe characteristics of CCLs in optical, X-ray and SZ measurements; calculate their predicted numbers for LCDM parameters and viable range of cluster mass functions and their uncertainties. Several to a few dozen predicted; depends on lensing triaxiality, through the c-M relation. Much larger number expected in the WL regime. A383 is a possible CCL: BG high-z structures magnified as seen in Subaru.
1108.4990
The Principle of Mediocrity
Vilenkin
Combine multiverse with the principle of mediocrity, where many inflationary bubbles with diverse properties are constantly being formed. Discuss origin of this worldview, possible observational tests, and implications for the beginning and end of the universe.
IPMU seminar (particle physics and string theory)
The monopole-vortex complex: dual gauge symmetry from flavor
Kenichi Konishi (Pisa U.)
* gauge theory: a type of field theory in which the Lagrangian is invariant under a continuous group of local transformations.
* QED is an abelian gauge theory with the symmetry group U(1) and has one gauge field, the EM field, with the photon being the gauge boson.
* non-Abelian: the standard model is a non-abelian gauge theory with the symmetry group U(1) x SU(2) x SU(3) and has a total of twelve gauge bosons: the photon, three weak bosons, and eight gluons.
1108.2287
On the origin of the Salpeter slope for the initial mass function
Oey
Suggest that intrinsic stellar IMF follows a power-law slope gamma=2, inherited from hierarchical fragmentation of molecular clouds into clumps and clumps into stars. The logarithmic Salpeter slope gamma=1.35 in clusters is the aggregate slope for all the star-forming clumps contributing to an individual cluster, and is steeper than the intrinsic slope within individual clumps within individual clumps because the smallest star-forming clumps contributing to any given cluster are unable to form the highest-mass stars.
UCB TAC seminar
3D simulations of solar surface: from limb to secular models
Laurent Piau (CEA-Saclay)
Stagger code: simulates 3D radiation hydrodynamics and magnetic field at the solar surface; addresses ionization effects, compressibility, solves equations of radiation transfer and induction. Solar model atmospheres computed with OPAL EoS using the most recent solar composition (?). Models account for the magnetic field. Offer means of interpreting observations of space borne missions dedicated to solar surface dynamics. Discuss impact of magnetism on limb darkening profile. Effects of surface convection = "the surface term" in helio- and astroseismology; it must be understood well, and that can be done through modeling.
1108.4905
The lensing properties of the Einasto profile
Retana-Montenegro, Frutos-Alfaro
* Einasto profile: describes 3d profile rho(r) ~ exp(-Ar^alpha)
* NFW profile: descries 3d profile
* Sersic profile: describes surface brightness (projected density)
Derives surface mass density, deflection angle, lens equation, deflection potential, magnification, shear and critical curves of Einasto profile, which is hard because it is non-analytic for general values of the Einasto index.
1108.4688
The impact of massive neutrinos on the abundance of massive clusters
Ichiki, Takada
Spherical top-hat collapse model for a mixed DM model that includes neutrinos of mass 0.05 to 0.1 eV. Take into account relative differences between the density perturbation amplitudes of radiation, baryon, CDM and neutrinos around the top-hat CDM overdensity, assuming adiabatic initial conditions. Also solve Boltzmann hierarchy equations to obtain time evolution of neutrino perturbations, including late-time NL gravitational potential. Presence of massive neutrion slows down the collapse of CDM overdensity: neutrinos cannot fully catch up with the NL CDM perturbation due to its large free-streaming velocity for the ranges of neutrino masses and halo masses considered. The CDM overdensity collapse time is well monitored by the linear-theory extrapolated overdensity, smoothed for a given halo mass scale, taking into account the suppression effect of the massive neutrinos on the linear growth rate. Presence of massive neutrinos of 0.05-0.1 eV cause significant decrease in the abundance of massive halos compared to model without the massive neutrinos: 25% for 1e15 Msun, or factor 2 for z=1.
1108.4864
Vesto Slipher and the First Galaxy Redshifts
Thompson
Hubble claimed credit of other astronomers (e.g., Slipher, Lemaitre, Humason...).
1108.4929
Cluster-Cluster lensing and the case of Abell 383
Zitrin, Rephaeli, Sadeh, Medezinski, Umetsu, Sayers, Nonino, Morandi, Molino, Czakon, Golwala
Assess the likelihood of cluster-cluster lensing (CCL). Describe characteristics of CCLs in optical, X-ray and SZ measurements; calculate their predicted numbers for LCDM parameters and viable range of cluster mass functions and their uncertainties. Several to a few dozen predicted; depends on lensing triaxiality, through the c-M relation. Much larger number expected in the WL regime. A383 is a possible CCL: BG high-z structures magnified as seen in Subaru.
1108.4990
The Principle of Mediocrity
Vilenkin
Combine multiverse with the principle of mediocrity, where many inflationary bubbles with diverse properties are constantly being formed. Discuss origin of this worldview, possible observational tests, and implications for the beginning and end of the universe.
IPMU seminar (particle physics and string theory)
The monopole-vortex complex: dual gauge symmetry from flavor
Kenichi Konishi (Pisa U.)
* gauge theory: a type of field theory in which the Lagrangian is invariant under a continuous group of local transformations.
* QED is an abelian gauge theory with the symmetry group U(1) and has one gauge field, the EM field, with the photon being the gauge boson.
* non-Abelian: the standard model is a non-abelian gauge theory with the symmetry group U(1) x SU(2) x SU(3) and has a total of twelve gauge bosons: the photon, three weak bosons, and eight gluons.
1108.2287
On the origin of the Salpeter slope for the initial mass function
Oey
Suggest that intrinsic stellar IMF follows a power-law slope gamma=2, inherited from hierarchical fragmentation of molecular clouds into clumps and clumps into stars. The logarithmic Salpeter slope gamma=1.35 in clusters is the aggregate slope for all the star-forming clumps contributing to an individual cluster, and is steeper than the intrinsic slope within individual clumps within individual clumps because the smallest star-forming clumps contributing to any given cluster are unable to form the highest-mass stars.
Day 68
Friday. Missed a connection to Zurich. Reading in Heathrow Airport.
1108.4411
Ultra-fine dark matter structure in the Solar neighbourhood
Fantin, Green, Merrifield
* how many parsecs to an AU? ... must be 3600 (or off by a factor of 2, depending on the defn). ...Actually, it's 206265 AU in a parsec. (1) I forgot about 360 degrees, and (2) to convert degrees to radians. 1 parsec is the distance to an object that moves 2 arcsec in 6 months (corresponds to 1arcsec movement for 1 AU).
Direct detection of DM on Earth depends on density and velocity distribution on milliparsec scale. Use cosmological merger tree to analyze the merger history of a MW-like system, to investigate the implications of any ultra-fine structure for direct DM detectors. Find velocity distribution of MW-like galaxy is almost smooth, due to overlap of many streams of particles generated by multiple mergers. Only mergers of 1e10M_sun can generate significant features in the ultra-local velocity distribution which can be detectable by current experiments.
* but how about seasonal variations, that are used in some of the DM detection experiments?
1108.4681
The serendipitous observation of a gravitationally lensed galaxy at z=0.9057 from the Blanco Cosmology Survey: The Elliot Arc
Buckley-Geer, Drabeck... YT Lin... A Rest, et al
Optical Blanco Cosmology Survey (BCS) found a high-z galaxy lensed by a massive galaxy cluster at z=0.3838. Confirmed with spectro with GMOS on 8m Gemini South. Use WL+SL, velocity dispersion, cluster richness N_200, fitting to an NFW cluster mass density profile: 3 independent mass estimates of the mass M_200 that are consistent with each other: 5.1 pm 1.3 e14 M_sun. NFW concentration c_200 = 5.4 (+1.4-1.1). Compare with LCDM sim, lensing selected clusters, and real sample of cluster lenses. Most are compatible for LCDM for lensing clusters. No evidence based on one system for an increased concentration compared to LCDM. Determine SFR measured from OII 3727 line, and find it to be modest for the given lens magnification.
1108.4136
Sterile neutrions with eV masses in cosmology -- how disfavoured exactly?
Hamann, Hannestad, Raffelt, Wong
In the minimal LCDM model, eV sterile neutrios strongly disfavoured because they contribute too much hot dark matter. However, if the LCDM model is extended to include additional degrees of freedom in addition to the sterile neutrinos, then the HDM constraint on sterile states i considerably relaxed. Further improvement with w<-1. BBN strongly disfavours extra radiation beyond the assumed eV-mass sterile neutrino, but this can be circumvented by a small nu_e degeneracy. Any model containing eV-mass sterile neutrinos implies strong modifications of other cosmological parameters: the inferred CDM density can shift up by 20 to 75% relative to the standard LCDM value.
* so this seems rather unlikely?
1108.4411
Ultra-fine dark matter structure in the Solar neighbourhood
Fantin, Green, Merrifield
* how many parsecs to an AU? ... must be 3600 (or off by a factor of 2, depending on the defn). ...Actually, it's 206265 AU in a parsec. (1) I forgot about 360 degrees, and (2) to convert degrees to radians. 1 parsec is the distance to an object that moves 2 arcsec in 6 months (corresponds to 1arcsec movement for 1 AU).
Direct detection of DM on Earth depends on density and velocity distribution on milliparsec scale. Use cosmological merger tree to analyze the merger history of a MW-like system, to investigate the implications of any ultra-fine structure for direct DM detectors. Find velocity distribution of MW-like galaxy is almost smooth, due to overlap of many streams of particles generated by multiple mergers. Only mergers of 1e10M_sun can generate significant features in the ultra-local velocity distribution which can be detectable by current experiments.
* but how about seasonal variations, that are used in some of the DM detection experiments?
1108.4681
The serendipitous observation of a gravitationally lensed galaxy at z=0.9057 from the Blanco Cosmology Survey: The Elliot Arc
Buckley-Geer, Drabeck... YT Lin... A Rest, et al
Optical Blanco Cosmology Survey (BCS) found a high-z galaxy lensed by a massive galaxy cluster at z=0.3838. Confirmed with spectro with GMOS on 8m Gemini South. Use WL+SL, velocity dispersion, cluster richness N_200, fitting to an NFW cluster mass density profile: 3 independent mass estimates of the mass M_200 that are consistent with each other: 5.1 pm 1.3 e14 M_sun. NFW concentration c_200 = 5.4 (+1.4-1.1). Compare with LCDM sim, lensing selected clusters, and real sample of cluster lenses. Most are compatible for LCDM for lensing clusters. No evidence based on one system for an increased concentration compared to LCDM. Determine SFR measured from OII 3727 line, and find it to be modest for the given lens magnification.
1108.4136
Sterile neutrions with eV masses in cosmology -- how disfavoured exactly?
Hamann, Hannestad, Raffelt, Wong
In the minimal LCDM model, eV sterile neutrios strongly disfavoured because they contribute too much hot dark matter. However, if the LCDM model is extended to include additional degrees of freedom in addition to the sterile neutrinos, then the HDM constraint on sterile states i considerably relaxed. Further improvement with w<-1. BBN strongly disfavours extra radiation beyond the assumed eV-mass sterile neutrino, but this can be circumvented by a small nu_e degeneracy. Any model containing eV-mass sterile neutrinos implies strong modifications of other cosmological parameters: the inferred CDM density can shift up by 20 to 75% relative to the standard LCDM value.
* so this seems rather unlikely?
1108.4173
Vector dark energy and high-z massive clusters
Carlesi, Knebe, Yepes, Gottloeber, Jimenez, Maroto
Detection of extremely massive clusters at z>1 has been considered by some authors as a challenge to the standard LCDM cosmology. Discuss probability of existence of such objects in light of the Vector Dark Energy (VDE) paradigm, where chances of detection substantially enhanced.
* Maybe a good filament project? check for filaments at high-z, and then check mass biases there.
1108.4314
Galaxy Disks are Submaximal
Bershady, et al
Measure disk contribution of 30 (nearly) face-on spirals from the DiskMass survey. Measure the velocity distribution of disk in the radial and the cylindrical axis direction: sigma(z, R=0) ~ 0.26 Vmax, which is consistent with sigma(z)/siamg(R) = 0.6, implying "submaximal disks". Disks in sample contribute only 15 to 30% of the dynamical mass within 2.2 disk scale-lengths (hR); percentages increase systematically with luminosity, rotation speed and redder color. Disk-to-total mass ratio is at most 50% even from the fastest rotating galaxies (Vmax > 300 km/s), the reddest rest-frame (B-K~4mag) and highest luminosity (M(K) < -26.5). Spiral disks in general should be maximal. Implies stellar M/L ratio (and hence accounting of baryons in stars) should be lowered by at least a factor of 3.
* I don't understand what it means for spirals to be "submaximal".
1108.3989
Three-Dimensional hydrodynamic core-collapse SNe simulations for an 11.2 M_sun star with spectral neutrino transport
Takiwaki, Kotake, Suwa
Show how the postbounce SNe dynamics are affected with spatial multi-dimensionality (3D sim vs 2D and 1D). Calculate with: energy-dependent treatment of the neutrino transport. Tracer-particle analysis show: maximum residency time of material in the gain region is longer for 3D due to non-axisymmetric flow (vs 2D): advantageous to obtain neutrino-driven explosions. Convective matter motions more violent in 3D, but emitted neutrino energies smaller due to enhanced cooling. Shock expansion tends to become more energetic for models with finer resolutions. 3D sims with higher numerical resolutions and more advanced treatment of neutrino transport and gravity are needed.
1108.4036
The long-term evolution of double white dwarf mergers
Shen, Bildsten, Kasen, Quartaert
Some simulation on two C/O white dwarfs of unequal mass. Should not result in a Type Ia SNe.
1108.2725
X-Ray and optical flux ratio anomalies in quadruply lensed quasars. II. Mapping the DM content in elliptical galaxies
Pooley, Rappaport, Balckburne, Schechter, Wambsganss
61 Chandra observations of 14 quadruply lensed quasars; observe flux ratio in x-ray, which gives clean determination of microlensing effects in the lensing galaxy. Local stellar fraction of 7%, the rest (93%) in a smooth, dark matter component (gas negligible?).
* is ignoring gas a good assumption? That's not true for galaxy clusters, is it?
1108.2842
What can the detection of single pair of circiles-in-the-sky tell us about the geometry and tolopgy of the Universe?
Mota, Reboucas, Tavakol
When the universe is *exactly* flat, then detection of non-trivial spatial topology doesn't have to be through detection of antipodal pairs of circles in the sky.
1108.2914
Exclusion of canonical WIMPs by the joint analysis of MW dwarfs with Fermi
Geringer-Sameth, Koushiappas
Generic WIMP candidates with M<27 GeV excluded.
2208.4128
Dominant Multipoles in WMAP5 Mosaic Data Correlation Maps
Verkhodanov, Khabibullina
ILC (?) map anomaly in the main plane and poles of ecliptic and equatorial coordinate systems. A dominant quadrupole contribution found.
Tuesday, August 23, 2011
Day 67
Wednesday. Talked to Mitra yesterday, but I know Rachel is busy this week, moving from NJ to CMU. I really want to get the shape catalog done...
1108.4021
The outskirts of globular clusters as modified gravity probes
Hernandez, Jimenez
* MOND picture: for a < a0, transition into MOND regime, where the equilibrium velocity scales as v^4 ~ M.
The MOND dropoff observed in outskirts of Galactic globular clusters. (?!? really?) Construct gravitational equilibrium dynamical models for these clusters: inner Newtonian region and outer modified gravity regime---reproduces observed half-light radii, total masses and LOS velocity dispersion profiles. Derive estimated total mass for each system; find asymptotic values of the velocity dispersion profiles consistent with scaling with the fourth root of the total masses, as expected from MOND.
* Which globular clusters are showing this? : Scarpa+ (2004, 2007, 2011)
NGC6171, NGC6341, NGC7078, NGC7099, NGC288
* What are their estimated mass?
* Is the acceleration smaller or larger than solar system velocity? : a0 ~ 1.2e-10 m/s^2
* Pioneer anomaly: At the edge of the solar system (20 AU = 3e9 km, where the Pioneer anomaly shows), unexplained acceleration towards the Sun of (8.74\pm1.33)e-10 m/s^2. Lunar laser ranging experiments have disproved MOND as the source of Pioneer anomaly.
* Is the v^4~M consistent with NFW profile mass distribution?
UCB SPI seminar
CO freeze-out and the origins of chemical complexity
Karin Oberg (CfA)
Organic molecules found in: low- and high-mass protostars, galactic center clouds, protostellar outflows, protoplanetary disks and comets. Demonstrates efficient astrophysical pathways to chemical complexity. Explore such pathways--constrain prebiotic chemistry during planetesimal formation and develop new tracers. Chemical evolution mostly takes place on interstellar grain surfaces, in icy mantles (?). Role of CO freeze-out for ice evolution from clouds to hot cores (?), and also its role in regulating the chemistry in protoplanetary disks. CO snowline in disks is important. Many results depend directly or indirectly on lab simulations of grain surface chemistry. New results on CO photodesorption; other experimental work required for ALMA.
1108.3950
The Cosmic Background Imager 2
Taylor et al.
* Cosmic Background Imager:
13 antennas, 0.9m replaced with 1.4m antennas. Excellent sidelobe and spillover performance at low cost. Off-the-shelf "spun primaries" used, secondary mirrors oversized, shaped relative to ... all these new improvements. Demonstrate performance of telescope and the inter-calibration with previous system using SZ effect on Abell 1689. Enhanced instruemt used to study the CMB, SZ and diffuse galactic emission.
1108.4021
The outskirts of globular clusters as modified gravity probes
Hernandez, Jimenez
* MOND picture: for a < a0, transition into MOND regime, where the equilibrium velocity scales as v^4 ~ M.
The MOND dropoff observed in outskirts of Galactic globular clusters. (?!? really?) Construct gravitational equilibrium dynamical models for these clusters: inner Newtonian region and outer modified gravity regime---reproduces observed half-light radii, total masses and LOS velocity dispersion profiles. Derive estimated total mass for each system; find asymptotic values of the velocity dispersion profiles consistent with scaling with the fourth root of the total masses, as expected from MOND.
* Which globular clusters are showing this? : Scarpa+ (2004, 2007, 2011)
NGC6171, NGC6341, NGC7078, NGC7099, NGC288
* What are their estimated mass?
* Is the acceleration smaller or larger than solar system velocity? : a0 ~ 1.2e-10 m/s^2
* Pioneer anomaly: At the edge of the solar system (20 AU = 3e9 km, where the Pioneer anomaly shows), unexplained acceleration towards the Sun of (8.74\pm1.33)e-10 m/s^2. Lunar laser ranging experiments have disproved MOND as the source of Pioneer anomaly.
* Is the v^4~M consistent with NFW profile mass distribution?
UCB SPI seminar
CO freeze-out and the origins of chemical complexity
Karin Oberg (CfA)
Organic molecules found in: low- and high-mass protostars, galactic center clouds, protostellar outflows, protoplanetary disks and comets. Demonstrates efficient astrophysical pathways to chemical complexity. Explore such pathways--constrain prebiotic chemistry during planetesimal formation and develop new tracers. Chemical evolution mostly takes place on interstellar grain surfaces, in icy mantles (?). Role of CO freeze-out for ice evolution from clouds to hot cores (?), and also its role in regulating the chemistry in protoplanetary disks. CO snowline in disks is important. Many results depend directly or indirectly on lab simulations of grain surface chemistry. New results on CO photodesorption; other experimental work required for ALMA.
1108.3950
The Cosmic Background Imager 2
Taylor et al.
* Cosmic Background Imager:
13 antennas, 0.9m replaced with 1.4m antennas. Excellent sidelobe and spillover performance at low cost. Off-the-shelf "spun primaries" used, secondary mirrors oversized, shaped relative to ... all these new improvements. Demonstrate performance of telescope and the inter-calibration with previous system using SZ effect on Abell 1689. Enhanced instruemt used to study the CMB, SZ and diffuse galactic emission.
1108.3343
The Atacama Cosmology Telescope: high-resolution SZ array observations of ACT SZE-selected clusters from the Equatorial Strip
Reese, Mroczkowski, et al
Follow-up observations with SZA of optically confirmed galaxy clusters found in the equatorial survey region of ACT (3 clusters). One of them is new--it's also massive (1e15 Msun) and at high-z (z=0.81). SZA observation probes broader range of spatial scales, disentangle cluster decrements from radio point source emission, derive more robust integrated SZE flux and mass estimates than ACT data alone. For 2 clusters, compute integrated SZE signal and derive masses from SZA data only. Abell 2631 has Chandra X-ray-based mass estimate; optical richness also used to estimate cluster masses, shows good agreement with SZE and X-ray. Based on the point sources in SZA, point source contamination is at the <=20% level from some fraction of clusters.
1108.3384
An indirect search from WIMPs in the Sun using 3109.6 days of upward-going muons in Super-K
Tanaka et al.
Search of high-E nu from WIMP annihilation in the Sun, using upmu events in Super-K. Dataset from SKI-SKIII. Searched for excess of nu signal from Sun, compared with expected atmospheric nu BG in three upmu categories: (1) stopping, (2) non-showering, (3) showering. No significant excess observed. Upper limit for muon flux from WIMP (100GeV) were ~5e-15 cm^-2 s^-1; limits spin-dependent WIMP-nucleon scatter cross section in the soft and hard annihilation channels to ~1e-39 cm^-2.
* current DM derection limits are ~1e-41.
1108.3486 (companion paper to 1108.2323)
The US Eclipse Megamovie in 2017: a white paper on a unique outreach event
Hudson, Mcintosh, Habbel, Pasachoff, Peticolas
* 2017: First total eclipse in the continental US since 1979. Another in 2024...
Total eclipse from Oregon to South Carolina. Totality lasts for an hour and a half. Good chance for very high time resolution movie of the event: contain unprecendented information about the physics of the solar corona.
1108.3541
Constraining the axion mass through the astroseismology of the ZZ Ceti star G117-B15A
CArsico, Althaus, Romero, Miller Bertolami, GarcAa-Berro, Isern
* DAV star:
Study astroseismology on the basis of a modern set of fully evolutionary DA white dwarf models with consistent chemical profiles at the core and envelope. Model that closely reproduces the observed pulsation periods of this particular star. Use measured rate of period change for the dominant mode of the pulsating star to impose preliminary upper limit to the mass of the axion. (how in the world do they do that??)
1108.3546
Constraining DM models from a combined analysis of MW satellites with the Fermi LAT
Fermi-LAT collaboration
* good, solid limits
Satelite galaxies of the MW: most promising targets for DM searches in gamma rays (large dynamical M/L ratio, small expected BG from astrophysical sources (i.e., we're not looking into a BH). Apply joint likelihood analysis to 10 satellite galaxies with 24 months of data of Fermi LAT. No DM signal detected. Uncertainty in the DM distribution in the satellites taken into account in deriving robust upper limits on DM models. Annihilation cross section range from 1e-26 cm^3 s^-1 at 5GeV to 5e-23 cm^3/s at 1TeV, depending on the DM annihilation final state. For the first time using gamma rays, able to rule out models with the most generic cross section (~3e-26 cm^3/s for a purely s-wave cross section), w/o assuming additional astrophysical or particle physics boost factors.
1108.3512
Towards a general description of the interior structure of rotating BH
Hamilton
Present a number of proposals about the interior structure (structure where?) of a rotating BH that is accreting slowly. Proposal can possibly be tested with numerical simulations. Triggers "mass inflation instability", which happens with the outgoing and ingoing particles free-falling in the parent Kerr geometry become highly focused along the principal null directions as they approach the "inner horizon" (?). Argue: gravitational waves should behaving in the geometric optics limit, and hence the spacetime should be almost shear-free. Full set of shear-free equations derived. A specific line-element is proposed; argue that it should provide a satisfactory approximation during early inflation. Argue: super-Planckian collision between outgoing and ingoing particles will lead to "entropy production" (?!) brining inflation to an end, and precipitating collapse (?).
* what is "inflation" in a rotating black hole?
* whatever.
1106.4018
Predicted constraints on cosmic string tension from Planck and fugure CMB polarization measurements
Foreman, Moss, Scott
Fisher matrix calculation on the error estimates of cosmic string tension Gmu from Planck and future CMB experiments. Simulations are more general then commonly used in the literature: mean velocity of strings, correlation length of the string network, "wiggliness" are left as free parameters that can be observationally measured. StringFast (new code): efficient computation of the C_l spectra induced by a network of strings. If string parameters left free, the projected constraings on Gmu are larger by x2-7. If Gmu is equal to the current observational maximum, Planck will be able to make a confident detection of strings (bah). If factor of 100 smaller, then cannot detect string tension.
* how does string tension affect C_l? It must leave WL-like signatures, I guess, and the tension give the stringth of such signal?
1108.3989
Three-dimensional hydrodynamic core-collapse SNe simulations for an 11.2 M_sun star with spectral neutrino transport
Takiwaki, Kotake, Suwa
Three-dimensional hydrodynamic core-collapse SNe simulations for an 11.2 M_sun star with spectral neutrino transport
Takiwaki, Kotake, Suwa
Monday, August 22, 2011
Day 66
Tuesday. Dad's BD dinner tonight, so will leave IPMU early today (4pm). Will I talk to Mitra or Rachel this week?
1108.2270
Tidal disruption rate of stars by supermassive black holes obtained by direct N-body simulations
Brockamp, Baumgardt, Kroupa
* How often do stars be tidally disrupted by SMBH?
Assume inital stellar distribution around SMBH as Sersic n=4 profile (bulge). 1e3 to 5e5 particles around SMBH; three different BH capture radii to allow scaling or results for SMBH up to M~1e6 Msun. Number of disrupted stars computed by diffusion in angular momentum space into the loss cone of BH; the rate scales with the total number of particles such that dN/dt ~ N^b, where b~0.83---steeper than the expected dN/dt ~ ln(N) derived from simple energy relaxation arguments. Only a realtively modest dependence of the tidal disruption rate on the mass of SMBH is found. The number of disrupted stars contribute a significant part of the mass growth of BH in the lower mass range if significant part of mass growth of BH is actually swallowed by the SMBH. Direct consequence for the search and existence of IMBHs in globular clusters. For SgrA* SMBHs, a tidal disruption rate of 55 +/- 27 events / Myr deduced. Relaxation driven stellar feeding cannot account for the masses of massive BHs with M > 1e7 M_sun.
* Not sure if the assuptions that went into the calculation is correct (i.e., Sersic distribution of stars; diffusion mechanism).
1108.2009
Hangup Kicks: still larger recoils by partial spin/orbit alignment of BH binaries
Lousto, Zlochower
Gravitational radiation recoil studied in configurations of final remanent of BH binary merger that have components of the spin both aligned with the orbital angular momentum and in the orbital plane. 24 new simulations for equal-mass and equal-spin-magintude binaries (but with different spin orientations). Include both new and known results. Predicted new maximum velocity is 5000 km/s (rather big v/c), where this is reached for spins partially aligned with the orbital angular momentum. Optimal configuration is near an equipartition of the hangup and superkick contributions. Newly discovered contribution to the recoil---increase the probabilities of large reciols in generic astrophysical mergers. Measure probabilities accretion-aligned spins and find non-negligible probabilities for SMBH encounters leading to recoil velocities of several thousand km/s.
* hangup? superkick?
* c = 3e5 km/s, so 5e3 km/s => beta = 1.7e-2
Sunday, August 21, 2011
Day 65
Monday. Lots to do before I leave Japan on Friday.
1108.2517
Weak Primordial Magnetic Fields and Anisotropies in the CMB Radiation
Jedamzik, Abel
* new tewt of primoridal magnetic fields using the CMB. Induces small scale but large baryon inhomogeneities. The RMS shift in recombination history would change in the CMB in a detectable way. Lowers the detection limit on primordial B-fields by at least 100-fold. (down to 1e-11G)
Small-scale magnitic fields present before recombination induce baryonic density inhomogeneities of appreciable magnitude. The presence of such inhomogeneities changes the ionization history of the universe (does it make ionization more inhomogeneous?), which in turn decrease the angular scale of the Doppler peaks (why?) and increases Silk damping by photon diffusion.
1108.3080
How unitary cosmology generalizes the thermodynamics and solves the inflationary entropy problem
Tegmark
* quantum entanglement: a form of quantum superposition, whose state is indefinite until a measurement is made. When a measurement is made on one member of the two initially interacting but subsequently separated pair, then the other member of this pair (the entangled pair) will take on a definite value. Verified experimentally.
2nd law of thermodynamics : "The system's entropy cannot decrease unless it interacts with the observer; cannot increase unless it interacts with the environment." Long-range entanglement created by cosmological inflation causes the cosmic entropy to decrease exponentially rather than linearly with the number of bits of information observed. Whatever.
1108.3332
Central Powering of the largest Lyman-alpha Nebula is revealed by polarized radiation
Hayes, Scarlata, Siana
* Lyman-alpha blob (LAB): a huge concentration of gas emitting the Ly-a emission line, generated by recombination of electrons with ionized hydrogen atoms.
High-z Lyman-alpha blobs: extended, luminous, rare structures; appears to be associated with the highest peaks in the matter density of the universe. Energy output an morphology similar to powerful radio galaxies, but source of luminosity unclear. Some seem to be associated with extreme starburst, while another possibility is gas that is shock-excited by supernovae. Some blobs not associated with galaxies, and could be heated by gas falling into a DM halo. Have detected polarization from LAB1: centralregions show no measurable polarization, while the polarization fraction increase to 20% at radius 45 kpc, formng an almost complete polarized ring. The detection of polarized radiation is inconsistent with the in situ production of Ly-a photons, and so the conclusion is that they must have been produced in the galaxies hosted within the nebula, and re-scattered by neutral H. (So the starburst scenario, eh?)
1108.3697
Using dwarf satellite proper motions to determine their origin
Angus, Diaferio, Kroupa
It's kinda hard to get these dwarf galaxies around MW to come in from a filament, given their current proper motion and assumed dynamical friction.
1108.3717
Halo shapes from WL: the impact of Galaxy-halo misalignment
Bett
Need quite a bit of galaxy-halo alignment for the halo shape to show in stacked gg-lensing analysis.
1108.2517
Weak Primordial Magnetic Fields and Anisotropies in the CMB Radiation
Jedamzik, Abel
* new tewt of primoridal magnetic fields using the CMB. Induces small scale but large baryon inhomogeneities. The RMS shift in recombination history would change in the CMB in a detectable way. Lowers the detection limit on primordial B-fields by at least 100-fold. (down to 1e-11G)
Small-scale magnitic fields present before recombination induce baryonic density inhomogeneities of appreciable magnitude. The presence of such inhomogeneities changes the ionization history of the universe (does it make ionization more inhomogeneous?), which in turn decrease the angular scale of the Doppler peaks (why?) and increases Silk damping by photon diffusion.
1108.3080
How unitary cosmology generalizes the thermodynamics and solves the inflationary entropy problem
Tegmark
* quantum entanglement: a form of quantum superposition, whose state is indefinite until a measurement is made. When a measurement is made on one member of the two initially interacting but subsequently separated pair, then the other member of this pair (the entangled pair) will take on a definite value. Verified experimentally.
2nd law of thermodynamics : "The system's entropy cannot decrease unless it interacts with the observer; cannot increase unless it interacts with the environment." Long-range entanglement created by cosmological inflation causes the cosmic entropy to decrease exponentially rather than linearly with the number of bits of information observed. Whatever.
1108.3332
Central Powering of the largest Lyman-alpha Nebula is revealed by polarized radiation
Hayes, Scarlata, Siana
* Lyman-alpha blob (LAB): a huge concentration of gas emitting the Ly-a emission line, generated by recombination of electrons with ionized hydrogen atoms.
High-z Lyman-alpha blobs: extended, luminous, rare structures; appears to be associated with the highest peaks in the matter density of the universe. Energy output an morphology similar to powerful radio galaxies, but source of luminosity unclear. Some seem to be associated with extreme starburst, while another possibility is gas that is shock-excited by supernovae. Some blobs not associated with galaxies, and could be heated by gas falling into a DM halo. Have detected polarization from LAB1: centralregions show no measurable polarization, while the polarization fraction increase to 20% at radius 45 kpc, formng an almost complete polarized ring. The detection of polarized radiation is inconsistent with the in situ production of Ly-a photons, and so the conclusion is that they must have been produced in the galaxies hosted within the nebula, and re-scattered by neutral H. (So the starburst scenario, eh?)
1108.3697
Using dwarf satellite proper motions to determine their origin
Angus, Diaferio, Kroupa
It's kinda hard to get these dwarf galaxies around MW to come in from a filament, given their current proper motion and assumed dynamical friction.
1108.3717
Halo shapes from WL: the impact of Galaxy-halo misalignment
Bett
Need quite a bit of galaxy-halo alignment for the halo shape to show in stacked gg-lensing analysis.
Friday, August 19, 2011
Day 64
Saturday. I want to write up my goals today.
LBL INPA
New insights on galaxy evolution since z~1.2 from the CFHT Legacy Survey
Jean Coupon, Tohoku University
Galaxies in low- and high-mass halos experience very distinct fate. Study relationship between stellar mass and halo mass brings valuable clues about physical processes involved in galaxy evolution. Halo model assumes that number of galaxies only depend on halo mass (HOD model), which seems to an accurate analytic prediction of galaxy distribution. Reciprocally, interpreting galaxy clustering using the HOD model allows to make a direct comparison between galaxy properties and halo mass. Use CFHTLS data to see the relationship evolve between the galaxy and DM haloes since z~1.2.
1108.1812
The Bolocam galactic plane survey VII: Characterizing the properties of massive star-forming regions
Dunham, Rosolowsky, Evans, Cyganowski, Urquhart
Toward the high column density regions targeted by BGPS (Bolocam galactic plane survey) with GBT, 72% of the targets (456) were found to have NH3(1,1) lines, demonstrating the high-column density features found there accurately predict the presence of dense gas (what was the original target criteria for BGPS?). Determine kinematic distance and resolved distance ambiguity (what's important about that?) of those with NH3. Locates the Scutum and Sagittarius spiral arms; number of sources detected peak at 4-5 kpc. Depending on the distance, the BGPS objects are mostly clumps, with some cores and clouds. The mean gas kinetic temperature is 15.6K; the NH3 column density and abundance decrease by an order of magnitude between 3 to 11 kpc from the Galaxy center. Similar distance objects have physical properties that are indistinguishable--suggest similarity in clump structure across the Galactic disk. Compared BGPS sources to criteria for efficient star formation. 48% of sample should be forming stars (including massive ones) with high efficiency and 87% contain subregions with should have efficient SF; find 67% of the sample exhibit signs of SF activity based on mid-IR information.
* what is the difference between cores, clumps and clouds?
1108.1796
The effects of a hot gaseous halo on disc thickening in galaxy minor mergers
Moster, Maccio, Somerville, Naab, Cox
Simulate (for the first time) diffuse, rotating, cooling, hot gaseous halo to hydro simulations of minor mergers. Effect of this new gaseous component on MW galaxy to its thickness on 1:10 and 1:5 mergers. For 1:10 mergers the thin disc scale does not show thickening (compared to isolated galaxies)--accretion of new cold gas leads to formation of massive new thin stellar disc that dominates the surface brightness profile. Disc thickening dominated by cold-gas induced SF--the thick disc is the old stellar disc that has been thickened in a minor merger at z>1 ("in this scenario")--the thin disc is the new stellar disc that forms after merger. Evolution of the scale height during a 1:5 merger--a thin disc can be present even after the merger, if enough hot (?) gas is avaliable. ...etc.
1108.2052
No wide spread of stellar ages in the Orion Nebula cluster
Jeffries, Littlefair, Naylor, Mayne
Disc signatures decay monotinically (on average) over timescales of only a few Myr--hence any spread in SF time distribtion should lead to clear differences in the age distribtions of stars with and without discs (if all stars are born with circumstellar discs). Any real age spread must be smaller than the median disc lifetime. For a log-normal age distribution, there is an upper limit of <0.14 dex (>2 sigma) to any real age dispersion, compared to ~0.4 dex implied by the HR diagram. If the mean age for ONC is 2.5 Myr, then 95% the low-mass stellar population should have ages 1.3-4.8 Myr. The obsered luminosity dispersion is caused by a combination of observational uncertainties and physical mechanisms that disorder the conventional relationship between luminosity and age for pre-main-sequence stars.
* ..but is there observational evidence (from stellar discs) that ONC stars all have similar ages? Or is this already true and known--but then the argument all depends on the rate of circumstellar disc dissipation rate? I wish they would explain.
1108.1786
Molecular gas around low-luminosity AGN in late-type spirals
Beoker, Schinnerer, Lisenfeld
UCB Astro Seminar
The Physics of Self-Regulated Star Formation
Andi Burkert
If star formation happened according to the simple cosmological sequence of DM halo collapse, to the gravitational collapse of cold, dense molecular gas that burst into stars, the galaxies should be burned out by now---which is in contrast to observations.
Physics of interstellar medium and star formation is still in its early phase of exploration; high-resolution observations provide insight into the complex structure of the turbulent interstellar medium and its various gas phases. Star formation history of molecular cloud regions like Taurus and Orion have been investigated in great detail; numerical simulations have achieved enough resolution and complexity to study the origin and evolution of turbulent molecular clouds and their fragmentation into stars and stellar clusters within the galactic environment.
First summarize the most puzzling and challenging questions of star formation, then discuss a new approach that links star formation in galaxies to their cosmic baryonic accretion history. Then present new numerical simulations by Dobbs+ (2011a,b) on the evolution of the molecular web in disk galaxies that provide new insight into the self-regulated evolution of the multi-phase interstellar medium and its condensation into stars.
* I should probably read the paper by Dobbs+ (2011a,b). Sounds interesting.
LBL INPA
New insights on galaxy evolution since z~1.2 from the CFHT Legacy Survey
Jean Coupon, Tohoku University
Galaxies in low- and high-mass halos experience very distinct fate. Study relationship between stellar mass and halo mass brings valuable clues about physical processes involved in galaxy evolution. Halo model assumes that number of galaxies only depend on halo mass (HOD model), which seems to an accurate analytic prediction of galaxy distribution. Reciprocally, interpreting galaxy clustering using the HOD model allows to make a direct comparison between galaxy properties and halo mass. Use CFHTLS data to see the relationship evolve between the galaxy and DM haloes since z~1.2.
1108.1812
The Bolocam galactic plane survey VII: Characterizing the properties of massive star-forming regions
Dunham, Rosolowsky, Evans, Cyganowski, Urquhart
Toward the high column density regions targeted by BGPS (Bolocam galactic plane survey) with GBT, 72% of the targets (456) were found to have NH3(1,1) lines, demonstrating the high-column density features found there accurately predict the presence of dense gas (what was the original target criteria for BGPS?). Determine kinematic distance and resolved distance ambiguity (what's important about that?) of those with NH3. Locates the Scutum and Sagittarius spiral arms; number of sources detected peak at 4-5 kpc. Depending on the distance, the BGPS objects are mostly clumps, with some cores and clouds. The mean gas kinetic temperature is 15.6K; the NH3 column density and abundance decrease by an order of magnitude between 3 to 11 kpc from the Galaxy center. Similar distance objects have physical properties that are indistinguishable--suggest similarity in clump structure across the Galactic disk. Compared BGPS sources to criteria for efficient star formation. 48% of sample should be forming stars (including massive ones) with high efficiency and 87% contain subregions with should have efficient SF; find 67% of the sample exhibit signs of SF activity based on mid-IR information.
* what is the difference between cores, clumps and clouds?
1108.1796
The effects of a hot gaseous halo on disc thickening in galaxy minor mergers
Moster, Maccio, Somerville, Naab, Cox
Simulate (for the first time) diffuse, rotating, cooling, hot gaseous halo to hydro simulations of minor mergers. Effect of this new gaseous component on MW galaxy to its thickness on 1:10 and 1:5 mergers. For 1:10 mergers the thin disc scale does not show thickening (compared to isolated galaxies)--accretion of new cold gas leads to formation of massive new thin stellar disc that dominates the surface brightness profile. Disc thickening dominated by cold-gas induced SF--the thick disc is the old stellar disc that has been thickened in a minor merger at z>1 ("in this scenario")--the thin disc is the new stellar disc that forms after merger. Evolution of the scale height during a 1:5 merger--a thin disc can be present even after the merger, if enough hot (?) gas is avaliable. ...etc.
1108.2052
No wide spread of stellar ages in the Orion Nebula cluster
Jeffries, Littlefair, Naylor, Mayne
Disc signatures decay monotinically (on average) over timescales of only a few Myr--hence any spread in SF time distribtion should lead to clear differences in the age distribtions of stars with and without discs (if all stars are born with circumstellar discs). Any real age spread must be smaller than the median disc lifetime. For a log-normal age distribution, there is an upper limit of <0.14 dex (>2 sigma) to any real age dispersion, compared to ~0.4 dex implied by the HR diagram. If the mean age for ONC is 2.5 Myr, then 95% the low-mass stellar population should have ages 1.3-4.8 Myr. The obsered luminosity dispersion is caused by a combination of observational uncertainties and physical mechanisms that disorder the conventional relationship between luminosity and age for pre-main-sequence stars.
* ..but is there observational evidence (from stellar discs) that ONC stars all have similar ages? Or is this already true and known--but then the argument all depends on the rate of circumstellar disc dissipation rate? I wish they would explain.
1108.1786
Molecular gas around low-luminosity AGN in late-type spirals
Beoker, Schinnerer, Lisenfeld
Study of molecular gas around low-luminosity AGN in 3 late-type spirals (bulge-less): transitions of gaseous CO clearly detected within the central kpc of all 3 galaxies. The CO emission is faint (expected from low SF activity). Face-on galaxies show elevated intensity ratio of CO(2-1)/CO(1-0) transitions compared to similar galaxies w/o AGN---unlikely due to a very compact CO source; speculate that energetically weak AGN can still impact the physcial state of surrounding gas. No tracers of dense molecular gas (e.g., HCN or HCO+), but can establish upper limits that lie at the low end of the range in more energetic AGN The derived gas density is less than n(H2) ~ 2e3 cm^-3, which is significantly lower than in most other newrby galaxies. Scarsity of dense gas suggests that the conditions for SF are poor in these nuclei. (duh)
* what is the connection between AGN, dense gas and SF? It seems that AGN triggers SF---or is it not a causal effect, but rather the results of a single cause (i.e., mergers)?
UCB Astro Seminar
The Physics of Self-Regulated Star Formation
Andi Burkert
If star formation happened according to the simple cosmological sequence of DM halo collapse, to the gravitational collapse of cold, dense molecular gas that burst into stars, the galaxies should be burned out by now---which is in contrast to observations.
Physics of interstellar medium and star formation is still in its early phase of exploration; high-resolution observations provide insight into the complex structure of the turbulent interstellar medium and its various gas phases. Star formation history of molecular cloud regions like Taurus and Orion have been investigated in great detail; numerical simulations have achieved enough resolution and complexity to study the origin and evolution of turbulent molecular clouds and their fragmentation into stars and stellar clusters within the galactic environment.
First summarize the most puzzling and challenging questions of star formation, then discuss a new approach that links star formation in galaxies to their cosmic baryonic accretion history. Then present new numerical simulations by Dobbs+ (2011a,b) on the evolution of the molecular web in disk galaxies that provide new insight into the self-regulated evolution of the multi-phase interstellar medium and its condensation into stars.
* I should probably read the paper by Dobbs+ (2011a,b). Sounds interesting.
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