1201.1502
Search for shocks in XMM-Newton observations of CIZA J2242.8+5301
Ogrean, Bruggen, Rottgering, Simionescu, Croston, van Weeren, Hoeft
Study of the ICM of the galaxy cluster CIZA J2242 with XMM-Newton, showing elongated (2Mpc) narrow (~50 kpc) radio relic ("Sausage"). A counter relic is also present, along with a faint, extended radio halo. Surface brightness profiles to the north and south of the center are almost identical in shape, supporting the hypothesis that the two merging clusters have almost equal masses and a small impact parameter. ICM on the inner side has low temperature (5keV), and jumps to temperatures >10keV above 500kpc. Jumps in temperature and pressure coincide with two symmetric "bumps" in the x-ray surface brightness profiles. Inner shocks do not cause detectable radio relics. The temperatures and pressures determined from the spectral fits depend strongly on the assumed abundance table and absorption model---speculate that this is a characteristic of all clusters at low Galactic latitudes.
1201.1503
Strong molecular hydrogen emission and kinematics of the multiphase gas in radio galaxies with fast jet-driven outflows
Guillard, et al
Observation of ionized and neutral gas outflows in radio galaxies suggest AGN radio jet feedback has a galaxy-scale impact on the host ISM, but still unclear how molecular gas is affected. Deep Spitzer IRS spectroscopy of 8 RGs show fast HI outflows, which have bright H2 mid-IR lines that cannot be accounted for by UV or X-ray heating. Suggests that the radio jet, which drives the HI outflow, is also responsible for the shock-excitation of the warm H2 gas. It does not share the kinematics of the ionized/neutral gas. The mid-IR ionized gas lines are systematically broader than the H2 lines. In 5 sources the NeII line (and to a lesser extent NeIII and NeV lines) exhibit blue-shifted wings that match the kinematics of the outflowing HI or ionized gas. The H2 lines do not show broad wings, except a few detections. Shows that H2 gas is inefficiently coupled to the AGN jet-driven outflow of ionized gas. Dissipation of a small fraction (<10%) of the jet kinetic power can explain the dynamical heating of the molecular gas; bulk of the warm molecular gas is not expelled from these galaxies.
1201.1504
On the C-to-O ratio measurement in nearby sunlike stars: implications for planet formation and the determination of stellar abundances
Fortney
C/O>0.8 measurements common around FGK stars, where C/O~0.55 in the Solar system. Suggest that the derived C/O ratios are overestimated. IR T-dwarf spectra could show how common high C/O is in the stellar neighborhood. Expect carbon-dominated rocky planets are rarer than suggested.
1201.1506
How much H and He is "hidden" in SNe Ib/c? I. Low-mass objects
Hachinger et al
H and He features in photospheric spectra have been used to infer the properties of Type IIb, Ib and Ic SNe and their progenitor stars. Most radiative transfer models neglect NLTE effects [???], where are extremely strong especially in the He-dominated zones. Present comprehensive set of model atmospheres for low-mass SNe IIb/Ib/Ic. How much He can be contained in SNe Ic (where He lines are not seen) can be addressed. Include effect of heating by fast electrons, represent iso-energetic explosions of the same stellar core with different massive H/He envelopes on top. Synthetic spectra suggest that 0.06-0.14 Msun of He and even smaller amounts of H suffice to optical lines to be present, unless ejecta asymetries play a major role. Strongly supports the conjecture that low-mass SNe Ic originate from binaries where progenitor mass loss can be extremely efficient.
1201.1508
An observational test of the Vainshtein mechanism
Hui, Nicolis
Vainshtein mechanism: screens modified gravities on small scales (making it observable only on cosmological scales). In galilen scalar that mediates a long-range force, non-GR stars carry the full scalar charge, while black holes carry none. Implies SMBH lags behind the galaxy if galaxy is free-falling in some external gravitational field, and can range up to 0.1 kpc for small galaxies. Cannot explain observed offset in M87 unless the scalar force is significantly stronger than gravity.
1201.1533
Merging galaxy clusters: offset between the SZ effect and x-ray peaks
Molnar, Hearn, Stadel
Subarcminute resolution SZ effect images compared with high resolution X-ray images of some clusters show significant offsets between the two peaks. Use N-body/hydro sims of merging galaxy clusters using FLASH to study offsets quantitatively. Find significant displacements result between the SZ and X-ray peaks for large relative velocities for all masses used in the simulations, for impact parameters of 100-250 kpc. SZ peak coincides with the peak in pressure times the LoS characteristic length [???], and not the pressure maximum (as it would for clusters in equilibrium). Peak in X-ray emission coincides with the density maximum of the main cluster. Morphology of the SZ signal and X-ray peaks change with viewing angle. Compare with CL0152-1357 WL observations, a large velocity of 4800 km/s necessary to explain observations. Conclude that an analysis of the morphologies of multi-frequency observations of merging clusters can be used to put meaningful constraints on the initial parameters of the progenitors.
1201.1538
Primordial power spectrum versus extension parameters beyond the standard model
Guo, Zhang
Reconstruct the shape of primordial power spectrum of curvature perturbations in extended cosmological models, including massive neutrions, extra relativistic species, or varying primordial He abundance, from WMAP, ACT and SPT. Find scale-invariant primordial spectrum disfavored even in the presence of massive neutrinos, but is acceptable if the effective number of relativistic species or the primordial hellium abundance is allowed to vary freely.
1201.1569
Lensing and X-ray mass estimates of clusters (SIMULATION)
Rasia, Meneghetti, Martino, Borgani, Bonafede, Dolag, Ettori, Fabjan, Giocoli, Mazzotta, Merten, Radovich, Tornatore
Comparison between WL and x-ray mass estimates of a sample of numerically simulated clusters. Skylens and X-MAS to generate optical and x-ray mock observations. Standard observational tools and methods used to recover the mass profiles of each cluster pojrection from mock catalogues. Investigate the dependence of the results on cluster morphology, environment, temperature inhomogeneity, and mass. WL masses obtained from the fit of the cluster tangential shear profiles with NFW functionals are biased low by 5-10% with a large scatter (10-25%). Show that scatter can be reduced by optimally selecting clusters either having regular morphology or living in substructure-poor environment. X-ray masses are biased low by a large amount (25-35%), evidencing the presence of non-thermal sources of pressure in the ICM and temperature inhomogeneity, but show a significantly lower scatter than WL-derived masses. The X-ray mass bias grows from the inner to outer regions of the clusters. Both biases are weakly correlated with the 3rd order power ratio, while a stronger correlation exists with the centroid shift. X-ray bias is strongly connected with temperature inhomogeneities.
* must quote in cluster paper.
1201.1616
CLASH: precise new constraints on the mass profile of abell 2261
Coe, Umetsu, Zitrin, Donahue, Medezinski, Postman, Carrasco, Anguita, Geller, Rines, Diaferio, Kurtz, Bradley, Koekemoer, Zheng, Nonino, Molino, Mahdavi, Lemze, Infante
Precisely constrain the inner mass profile of Abell 2261 (z=0.225) for the first time, and determine this cluster is not "over-concentrated" as found previously, based on new HST 16-band imaging as part of CLASH. Combine with Subaru + KPNO photometry, place tight new constraints on the halo virial mass M_vir 2.2pm0.2e15 Msun/h70 and concentration c=6.2 assuming a spherical halo. Agrees broadly with average c(M,z) predictions from LCDM simulations which span 5-8. Most significant uncertainty is halo elongation along the LoS. To estimate, derive a mass profile based on archival Chandra and find it to be !35% lower than lensing-derived profile at r2500~600kpc. Agreement achieved by halo elongated with 2:1 axis ratio along LoS. For this model, Mvir=1.7pm0.2e15Msun/h70 and c=4.6, placing rough lower limits on these values. Need for halo elongation can be partially obviated by non-tehrmal pressure support and by systematic errors in the X-ray mass measurements. Estimate the effect of BG structures based on MMT spectro-z and find these tend to lower Mvir further by 7% and increase c by 5%.
* also must quote in cluster paper. They used our KPNO data!
1201.1617
Galaxy formation in WDM cosmology
Menci, Fiore, Lamastra
Effects of WDM power spectrum on the statistical properties of galaxies using SAM. WDM spectrum is suppressed (compared to CDM) below a cut-off scale of ~1Mpc, corresponding to a mass m=0.75keV, consistent with WMAP bounds and Lya forest. Predicted color distribution (from stellar mass distributions over a range of cosmic epochs) compared to CDM case, the luminosity and stellar mass distributions are characterized by: (1) a flattening of the faint end slope [of course], and (2) a sharpening of the cutoff at the bright end for z<0.8. Latter is related to the smaller number of satellite galaxies accumulating in massive haloes at low redshift, thus suppressing the accretion of small lumps on the central, massive galaxies.
1201.1660
Origin of TeV galactic CRs
Neronov, Semikoz
CR of energy above 1TeV via observation of degree-scale extended gamma-ray emission which traces the location of recent sources in Galaxy. Energy above 100 GeV is produce by CR nuclei and electrons released by the sources and spreading into the interstellar medium. Data from Fermi gamma-ray telescope to locate the degree-scale 100 GeV gamma-ray sources in Galactic Plane, find that large fraction of the sources is associated to pulsars with spin down age less than 30kyr and hence to the recent SNe explosions. Supports hypothesis of SNe origin of Galactic CRs. Degree-scale extended emission does not surround shell-like supernova remnants without pulsars. Based on this observation, argue that the presence of pulsar is essential for the CR acceleration process.
* SNe and pulsar remnants are the origin of Galactic CRs.
1201.1673
A journey from the outskirts to the cores of groups I: Color- and mass-segregation in 20K-zCOSMOS groups
Presotto, et al
zCOSMOS spectra catalog, investigate color and mass segregation in groups. Color segregation found in small groups, but not massive ones. Mass segregation found in large groups, but not smaller ones. Mass segregation due to dynamical friction.
* SF quenching taking place slower in low mass groups, while probably instantaneous in massive groups.
1201.1677
The SWELLS survey. III. Disfavouring "heavy" initial mass functions for spiral lens galaxies
Brewer, Dutton, Treu, Auger, Marshall, Barnabe, Bolton, Koo, Koopmans
Present gravitational lens models for 20 SL systems based as part of Sloan WFC Edge-on Late-type Lens Survey (SWELLS) project. For each system, compare the total mass inside the critical curve inferred from gravitational lens modelling to the stellar mass inferred from SPS models, compute stellar mass fraction within critical curve. Find for lower mass systems, Salpeter IMF leads to estimates of the stellar mass fraction that exceed 1 (unphysical). IMF is lighter with 98% probability, consistent with Chabrier IMF. Combined with heavier IMF inferred from lensing and dynamical analysis of more massive early-type lens galaxies from the SLACS sample, result provides strong evidence against a universal stellar IMF.
1201.1680
On the consistency of neutron-star radius measurements from the thermonuclear bursts
Galloway, Lampe
Radius of NSs can in principle be measured via the normalization of a BB spectra fitted to the X-ray spectrum during thermonuclear (type-I) X-ray bursts, although few studies have addressed the reliability of such measurements. Examine the apparent radius in homogeneous sample of long, mixed H/He bursts from the low-mass X-ray binaris GS1826-24 and KS 1731-26. The measured BB normalization (proportional to the emitting area) in these bursts is constant over a period of up to 60s in the burst tail, even though the flux (BB temperature) decreased by a factor of 60-75% (30-40%). The typical RMS variation in the mean normalization from burst to burst was 3-5%, although a variation of 17% was found between bursts observed from GS 1826-24 in two epochs. A comparison of the time-resolved spectroscopic measurements during bursts from the two epochs show that normalization evolves consistently through the burst rise and peak, but subsequently increase further in the earlier epoch bursts [???]. The elevated normalization values may arise from a change in the anisotropy of the burst emission, or alternatively variations in the spectral correction factor, f_c, or order 10%. Since burst samples observed from systems other than GS1826 are more heterogeneous, expect that systematic uncertainties of at least 10% are likely to apply generally to measurements of NS radii, unless the effects described here can be corrected for.
1201.1692
The SWELLS survey. IV. Precision measurements of stellar and DM distributions in a spiral lens galaxy
Barnabe, Dutton, Marshall, ... et al
Self-consistent mass model for the lens galaxy J2141 at z=0.14 and use it to improve on previous studies by modelling its gravitational lensing effect, gas rotation curve and stellar kinematics simultaneously. Adopt a very flexible axisymmetric mass model constituded by generalized NFW DM halo and a stellar mass distribution obtained by deprojecting the MGE fit to high resolution K'-band LGSAO imaging of galaxy, with the (spatilly constant) M/L ratio as a free parameter. Model the stellar kinematics by solving the anisotropic Jeans equations. Find inner logarithmic slope of dark halo weakly constrained (gamma = 0.82pm0.5) and consistent with unmodified NFW profile. Infer (1) DM fraction within 2.2 disk radii of 0.28pm0.1 (maximal disk), (2) an apparent uncontracted DM halo, with concentration 7.7 pm 3 and v_vir-242 km/s, (3) a lightly oblate halo (0.75), consistent with predictions from baryon-affected models. Comparing the stellar mass inferred from the combined analysis (M* = 1e11.1 Msun) with that inferred from SPS modeling of galaxy colors, and accounting for cold gas fraction of 20pm10%, determine a preference for a Chabrier IMF over Salperter IMF by a Bayes factor of 5.7 (substantial evidence). ...
* Reina's DM fraction within 2.2:
1201.1700
H I Epoch of reionization arrays
Greenhill, Bernardi
IGM thermal history following global recombination are currently constrained by CMB and optical spectroscopy along a few LoS, but direct study of IGM in emission or absorption against CMB via the 1S hyperfine transition of H would enable broad characterization thermal history and source populations. FOr new generation of radio arrays.
1201.1800
SHARDS: survey for high-z absorption red & dead sources
Perez-Gonzalez, Cava, the SHARDS team
GOODS-N field spectro-photometric survey with GTC/OSIRIS for z=1.0-2.3 sources using 24 medium band filters covering 500-950nm spectral range. Used to: (1) derive an unbiased sample of high-z quiescent galaxies, (2) derive accurate ages and stellar masses based on robust measurements of spectral features such as Mg(UV) or D(4000) indicies, (3) measure z with accuracy Delta(z)/(1+z)<0.02, and (4) study emission-line galaxies (starbursts and AGN) up to very high redshifts.
1201.1803
Constraints on the neutrino mass from SZ surveys
Shimon, Rephaeli, Itzhaki
Statistical measures of galaxy clusters are sensitive to neutrino masses in the sub-eV range. ... analysis show that if the (total) neutrino mass is close to the lower limits deduced from neutrino oscillation experiments, cluster number counts provide a viable complimentary cosmological probe to CMB lensing constraints on M_nu.
No comments:
Post a Comment