MPIfR Special Colloquium (Nov. 7, 11:00)
From spherical cows to modified Newtonian gravity
Robert Dickman
Milgrom pointed out in 1983 that MOND can explain galactic rotation curves without dark matter. MOND useful as economical modeling tool for galaxy rotation curves, and have predicted number of other regularities in the behavior of disk and ellipsoidal galactic systems (TF and FJ relations). In its Lagrangian formulation, nonlinearity is encoded by the ratio of total gravitational acceleration to a new fundamental acceleration scale, and under certain conditions, a system in equilibrium whose internal acceleration is below this scale may exhibit novel properties whose presence depends on the magnitude of the external gravitational field in which the system lies. This "external field effect" (EFE) can lead to phenomena that include morphological elongations as well as amplifications of the internal gravitational field. These signature effects can be suppressed by a sufficiently strong external gravitational field. The rarity of suitably simple test objects ("spherical cows") and the smallness of Milgrom's constant, have made difficult to test MOND EFE predictions observationally. Discuss some recent observational results and potential implications.
1111.0004
Modelling of the "Pi of the Sky" detector
Piotrowski (thesis)
Important to get the PSF right, for this wide FOV transient survey. The Zernike polynomial description of the PSF works pretty well, and although the photometry doesn't change, astrometry betters by x2.
1111.0005
Towards improving the prospects for coordinated gravitational-wave and electromagnetic observations
Mandel, Kelley, Ramirez-Ruiz
Detect GW, and follow-up with EM, or detect EM transients, and look for GW. Optimal methods discussed for each.
1111.0006
Optical spectroscopy of Halpha filaments in cool core clusters: kinematics, Reddening, and sources of ionization
McDonald, Veilleux, Rupke
High spatial and spectral resolution observation of Halpha nebulae in cool cores of 9 galaxy clusters: show that the emission are due to a composite of slow shocks and star formation (collisional ionization by CR, thermal conduction, and photoionization by ICM X-ray and AGN are ruled out as strong contributors, based on line ratios). Radial dependence of the velocity width probably linked with ICM turbulence. Central regions (r<10kpc) of several (warm gas) systems show kinematic signatures consistent with rotation. Kinematics of the most extended filaments in this sample are broadly consistent with both infall and outflow, and recommend further studies lining the warm gas kinematics to both radio and X-ray maps in order to further understand the observed kinematics.
1111.0007
A revised View of the transient radio sky
Frail, Kulkarni, Ofek, Bower, Nakar
Past long-duration radio transients reported by Bower and others are actually instrumental artifacts, whose SNR is rather low. There isn't as many true transients as initially reported, and must be careful in "detecting" things likes these in the future.
1111.0009
The X-ray luminous galaxy cluster population at 0.9<z<~1.6 as revealed by the XMM-Newton Distant Cluster Project
Fassbender ,Boehringer, ... et al
22 high-z clusters detected in XDCP, 2 of them new. Photo-z (z-H color) works pretty well to z~1.5, while R-z color only good till z~9. The z>0.9 systems usually do not harbor a central dominant galaxy coincident with the X-ray centroid position but rather exhibit significant BCG offsets from the X-ray center with a median value of about 50kpc in projection; and a msller median luminosity gap to the second-ranked galaxy of ~0.3 mag. Estimate fraction of cluster-associated NVSS 1.4 Ghz radio sources of about 30%, preferentially located within 1' from the X-ray center. Galaxy populations in z>1.5 cluster environments show first evidence of drastinc changes on the high-mass end of galaxies and signs for a gradual disappearance of a well-defined cluster red-sequence as strong SF activity is observed in an increasing fraction of massive galaxies down to the densest core regions.
1111.0013
Bayesian Cluster Finder: Clusters in the CFHTLS Archive research survey
Ascaso, Wittman, Benitez
New technique for detecting galaxy clusters based on Matched Filter Algorithm from a Bayesian point of view. Method: determine position, redshift and richness of the cluster through the maximization of a filter depending on galaxy luminosity, density and photometric redshift combined with a galaxy cluster prior that accounts for color-magnitude relations and BCG-redshift relation. Tested the algorithm through realistic mock galaxy catalogs, revealing that the detections are 100% complete and 80% pure; applied to CFHTLS archive research survey data, and recovered detections as previously published, plus additional clusters which appear to be real.
1111.0014
Kinematics and chemistry of stars along the sagittarius trailing tidal tail and constraints on the MW mass distribution
Carlin, Majewski, Casetti-Dinescu, Law, Girard, Patterson
3d kinematics of Sgr trailing tidal debris in 6 fields along the stream from Sgr dwarf galaxy core. Proper motion (PM) from Kapteyn, and radial velocity (RV) from spectroscopic follow-up. Compare to predictions of Law & Majewski (2010) model of Sgr disruption; find reasonable agreement with model predictions in RVs and PMs along galactic latitude. However, an upward adjustment of the local standard of rest velocity from the standard 220 km/s to possibly up to 264pm23 km/s is necessary to bring 3-d model debris kinematics and measurements into agreement. Satisfactory model fits that simultaneously reproduce known position, distance, and radial velocity trends of the Sgr tidal streams while significantly increasing the local standard rest velocity can only be achieved by increasing the Galactic bulge and disk mass, while leaving the dark matte rhalo fixed to the best-fit values from Law & Majewski (2010). Derive low-resolution spectroscopic abundances along this stretch of the Sgr stream; find a constant [Fe/H]=-1.15 with ~0.5 dex scatter; typical for dwarf galaxy populations. Constant metallicity suggests that debris along the ~60 deg span of this study was all stripped from Sgr on the same orbital passage.
1111.0020
The gas distribution in galaxy cluster outer regions
Eckert, Vazza, Ettori, Molendi, Nagai, Lau, Roncarelli, Rosseti, Snowden, Gastaldello
Low-z (0.04~0.2) sample of 31 galaxy clusters, measure X-ray emitting gas density in cluster outskirts. Compare results with numerical simulations, set constraints on azimuthal symmetry and gas clumping in the outer regions of galaxy clusters. Stacking of density profiles to detect a signal beyond r200 and measure the typical density and scatter in cluster outskirts. Also compute azimuthal scatter of the profiles with respect to the mean value to look for deviations from spherical symmetry. Compare average density and scatter profiles iwth the results of numerical simulations. As opposed to recent Suzaku results but confirming evidence from ROSAT and Chandra, we observe a steepening of the density profiles beyond ~r500. Comparing our density profiles with simulations, find non-radiative runs predict too steep density profiles, whereas runs including additional physics and/or treating gas clumping are in better agreement with the observed gas distribution. Report first high-confidence detection of a systematic difference between cool-core and non-cool core clusters beyond ~0.3 r200, which is explained by a different distribution of the gas in the two classes. Beyond ~r500, galaxy clusters deviate significantly from spherical symmetry, with only little differences between relaxed and disturbed systems. Find good agreement between the observed and predicted scatter profiles, but only when the 1% densest clumps are filtered out in the simulations.
1111.0028
Ring galaxies from off-center collisions
Mapelli, Mayer
Investigate formation of RE galaxies (of collisional rings galaxies with an empty ring) with N-body/SPH simulations. Employ recipe for SF and feedback that has been shown to be crucial to produce realistic galaxies in a cosmological context. Show that RE galaxies can form via off-centre collisions, even for small inclination angles. Ring can be either a complete ring or an arc, depending on the initial conditions (especially on the impact parameter). In simulations, the nucleus of the target galaxy is displaced from the dynamical centre of the galaxy and is buried within the ring, as a consequence of the off-centre collision. ... Interaction enhances the SF rate. Compare results to Arp 147, the prototype of RE galaxies.
1111.0052
General requirements on matter power spectrum predictions for cosmology with WL tomography
Hearin, Zentner, Ma
Constraining w at the percent level with DES, LSST, WFIRST, Euclid: reliance on photoz constitutes a major source of uncertainty for these surveys. Interpreting WL signal requires a detailed understanding of the nonlinear physics of gravitational collapse. Present new analysis of the stringent calibration requirements for Wl analysis for future imaging surveys that addresses both photoz uncertainty and errors in the calibration of the matter power spectrum. Find when photoz uncertainty is taken in to account, the requirements on the level of precision in the prediction for the matter power spectrum are more stringent than previously thought. Including degree-scale galaxy clustering statistics in a joint analysis with WL not only strengthens the survey's constraining power by ~20% but can also have a profound impact on the calibration demands, decreasing the rate of degradation in dark energy constraints with matter power spectrum uncertainty by a factor of 2-5. Similarly, using galaxy clustering information significantly relaxes the demands on the photo-z calibration. Compare these calibration requirements to the best photoz estimation and predictions of the power spectrum, and suggest strategies to utilize forthcoming data optimally.
* I should read this.
1111.0061
The Lick AGN monitoring project 2011: Reverberation mapping of Markarian 50
Barth,... Suzuki, ... et al
Observing campaign over 11 weeks in Spring of 2011. Mrk 50 highly variable by a factor of 4 in the U-band continuum and factor of 2 in the H beta line. Find H-beta and H-gamma lag the V-band continuum by 10 and 8 (pm1) days, respectively, while the lag of He II 4686 is unresolved. The H-beta line exhibits a symmetric velocity-resolved reverberation signature with shorter lags in the high-velocity wings than in the line core [too much jargon], consistent with an origin in a broad-line region dominated by orbital motion rather than infall or outflow. Assuming a virial normalization factor of f=5.25, the virial estimate of the BH mass is 3e7 Solar masses. Observations demonstrate the Mrk 50 is among the most promising nearby AGN for detailed investigations of broad-line region structure and dynamics.
1111.0099
Baryons in the outskirts of the X-ray brightest galaxy cluster
Simionescu, Allen, Mantz, Werner, Takei
Results from Suzaku observations of the Perseus Cluster, which provide best measurements of the thermodynamic properties of the ICM at large radii to date. In particular, focus on the details of the data analysis procedure and discuss the evidence for a clumpy distribution of the gas in the outskirts, which is important for understanding the physics of the ongoing growth of clusters from the surrounding cosmic web.
* Similar results (about the clumpy gas in the outskirts) to 1111.0020.
Baryons in the outskirts of the X-ray brightest galaxy cluster
Simionescu, Allen, Mantz, Werner, Takei
Results from Suzaku observations of the Perseus Cluster, which provide best measurements of the thermodynamic properties of the ICM at large radii to date. In particular, focus on the details of the data analysis procedure and discuss the evidence for a clumpy distribution of the gas in the outskirts, which is important for understanding the physics of the ongoing growth of clusters from the surrounding cosmic web.
* Similar results (about the clumpy gas in the outskirts) to 1111.0020.
1111.0132
A novel method to identify AGNs based on emission line excess and the nature of low-luminosity AGNs in the SDSS: I - A Novel Method
Takana
New method to identify low-luminosity AGN in SDSS. Emission line is a sum of star formation component and AGN component (if present). Demonstrate an accurate estimate of the SF component by fitting model spectra, generated with a recent stellar population synthesis code, to a continuum. Compare observed total line luminosity with that from SF, identify existence of AGN. Compare method with commonly used emission line diagnostics by Baldwin et al (1981, BPT); new method recovers the same star formation/AGN classification as BPT for 85% of the strong emission line objects (43% of sample). Unique feature of new method is sensitivity: applicable to 78% of the sample. Further make comparisons between new method and BPT using stacked spectra and selection in X-ray and radio wavelengths, show the method suffers from incompleteness and contamination as any AGN identification methods do, it is overall sensitive method to identify AGNs. Unique feature: allows us to subtract emission line luminosity due to SF and extract intrinsic AGN luminosity. Paper II studies the nature of low-luminosity AGNs selected in this way.
1111.0133
Paper II (cf above): - Nature of low luminosity AGNs
Tanaka
AGNs typically show extinction of tauV=1.2 and exhibit a wide range of ionization levels, which requires the use of [OII] + [OIII] luminosity as an indicator of AGN power Find AGNs are preferentially located in massive, red, early-type galaxies [really?]. Carefully take into account a selection bias of Oxygen-excess method, and show that strong AGNs are located in actively SF galaxies and rapidly growing SMBHs are located in rapidly growing galaxies, which clearly shows the co-evolution of SMBH and the host galaxies. [why are they contradicting each other about which galaxy types AGNs form?]. AGN power does not strongly correlate with the host galaxy mass. Mass works like a 'switch' to activate AGNs. Absence of AGNs in low-mass galaxies might be due to the absence of SMGHs in these galaxies, but a dedicated observaton of nuclear region of nearby low-mass galaxies are necessary for more insight.
1111.0166
Galaxy and Mass assembly (GAMA): ugriz galaxy luminosity functions
Loveday, ... et al
At low z (z<0.1), find blue galaxies are reasonably well fit over a range of more than 10 magnitudes by simple Schechter functions in all bands. Red galaxies and the combined (red+blue) sample require double power-law Schechter functions to fit a dip in their LF faintward of he characteristic magnitude M* before a steepening faint end. This upturn is at least partly due to dust-reddened disk galaxies. Measure z evolution of the galaxy LF to z<0.5 using both a parametric fit and by measuring binned LFs in redshift slices. Characteristic luminosity L* is found to increase with redshift in all bands, with red galaxies showing stronger luminosity evolution than blue galaxies. Blue galaxies, as well as being more numerous at high z, dominate the overall luminosity density beyond redshifts z=0.2. At lower redshifts, the luminosity density is dominated by red galaxies in the riz bands, and by blue galaxies in u and g.
A novel method to identify AGNs based on emission line excess and the nature of low-luminosity AGNs in the SDSS: I - A Novel Method
Takana
New method to identify low-luminosity AGN in SDSS. Emission line is a sum of star formation component and AGN component (if present). Demonstrate an accurate estimate of the SF component by fitting model spectra, generated with a recent stellar population synthesis code, to a continuum. Compare observed total line luminosity with that from SF, identify existence of AGN. Compare method with commonly used emission line diagnostics by Baldwin et al (1981, BPT); new method recovers the same star formation/AGN classification as BPT for 85% of the strong emission line objects (43% of sample). Unique feature of new method is sensitivity: applicable to 78% of the sample. Further make comparisons between new method and BPT using stacked spectra and selection in X-ray and radio wavelengths, show the method suffers from incompleteness and contamination as any AGN identification methods do, it is overall sensitive method to identify AGNs. Unique feature: allows us to subtract emission line luminosity due to SF and extract intrinsic AGN luminosity. Paper II studies the nature of low-luminosity AGNs selected in this way.
1111.0133
Paper II (cf above): - Nature of low luminosity AGNs
Tanaka
AGNs typically show extinction of tauV=1.2 and exhibit a wide range of ionization levels, which requires the use of [OII] + [OIII] luminosity as an indicator of AGN power Find AGNs are preferentially located in massive, red, early-type galaxies [really?]. Carefully take into account a selection bias of Oxygen-excess method, and show that strong AGNs are located in actively SF galaxies and rapidly growing SMBHs are located in rapidly growing galaxies, which clearly shows the co-evolution of SMBH and the host galaxies. [why are they contradicting each other about which galaxy types AGNs form?]. AGN power does not strongly correlate with the host galaxy mass. Mass works like a 'switch' to activate AGNs. Absence of AGNs in low-mass galaxies might be due to the absence of SMGHs in these galaxies, but a dedicated observaton of nuclear region of nearby low-mass galaxies are necessary for more insight.
1111.0166
Galaxy and Mass assembly (GAMA): ugriz galaxy luminosity functions
Loveday, ... et al
At low z (z<0.1), find blue galaxies are reasonably well fit over a range of more than 10 magnitudes by simple Schechter functions in all bands. Red galaxies and the combined (red+blue) sample require double power-law Schechter functions to fit a dip in their LF faintward of he characteristic magnitude M* before a steepening faint end. This upturn is at least partly due to dust-reddened disk galaxies. Measure z evolution of the galaxy LF to z<0.5 using both a parametric fit and by measuring binned LFs in redshift slices. Characteristic luminosity L* is found to increase with redshift in all bands, with red galaxies showing stronger luminosity evolution than blue galaxies. Blue galaxies, as well as being more numerous at high z, dominate the overall luminosity density beyond redshifts z=0.2. At lower redshifts, the luminosity density is dominated by red galaxies in the riz bands, and by blue galaxies in u and g.
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