Saturday. Sunday.
1310.7020
Exploring the chemical link between local ellipticals and their high-redshift progenitors
Leja, van Dokkum, … Franx, Kriek, … Bezanson, Conroy, … et al
K-band spectroscopy of mass-selected, 6 galaxies at z~2.3; have mean [NII]/Ha ratio of 0.27 pm 0.01. Mean value similar to that of UV-selected galaxies of the same mass. The man gas-phase oxygen abundance inferred from the [NII]/Ha ratios depends on the calibration method, and ranges from 12+log(O/H)_gas=8.57 to 8.87 [what's the typical variation within a sample of galaxies?]. Measurements of stellar oxygen abundance in nearby quiescent galaxies with the same number density indicate 8.95, similar to the gas-phase abundances of the z~2.3 galaxies (if using the latter calibration method). Suggests that these high-z SF galaxies may be progenitors of today's massive early-type galaxies. The main uncertainties are the absolute calibration of the gas-phase oxygen abundance and the incompleteness of the z~2.3 sample: the galaxies with detected Ha tend to be larger and have higher SFRs than the galaxies without detected Ha, and may still be missing the most dust-obscured progenitors.
1310.7022
The peculiar pulsar population of the central parsec
Dexter, O'Leary
No pulsar (ordinary or millisecond) found within 25 pc of the Galactic center Sgr A*, although it would be useful to test GR. Explanation: hyper strong temporal scattering prevents pulsar detections, but a recent discovery of radio pulsations from a magnetar within 0.1 pc shows that the temporal scattering [?] is much weaker than predicted. Argue that an intrinsic deficit in the ordinary pulsar population is the most likely reason for the lack of detections to date: a "missing pulsar problem" in the Galactic center. In contrast, discovery of a single magnetar implies efficient magnetar formation in the region. If the massive stars in the central parsec form magnetars rather than ordinary pulsars, their short lifetimes could explain the missing pulsars. Efficient magnetar formation could be caused by strongly magnetized progenitors, or could be further evidence of a top-heavy IMF. Current high-frequency surveys should already be able to detected bright millisecond pulsars, given the measured degree of temporal scattering.
1310.7023
CMB lensing power spectrum biases from Galaxies and clusters using high-angular resolution temperature maps
Engelen, … Holder, Zahn, Nagai
Study several types of biases to the temperature-based lensing reconstruction signal from FG sources such as radio and IR galaxies in the SZ effect from galaxy clusters. These FGs bias the CMB lensing signal due to their non-Gaussian nature. Using simulations as well as some analytical models, find that these sources can substantially impact the measured signal if left untreated. However, these biases can be brought to the percent level if one masks galaxies with fluxes at 150 GHz above 1mJy and galaxy clusters with masses above M_vir=1e14 Msun. To achieve such percent level bias, find that only modes up to a maximum multipole of L_max~2500 should be inlaced in the lensing reconstruction. Also discuss ways to minimize additional bias induced by aggressive FG masking by, for example, exploring a two-step masking and in-painting algorithm.
1310.7031
What next-generation 21 cm power spectrum measurements can teach us about the epoch of reionization
Pober, Liu, … Aguirre, … McQuinn, … Parsons, Tegmark, et al
…find that 0.1 km&2 of collecting area is enough to ensure a ~30 sigma detection of the reionization PS in even the most pessimistic scenarios. This sensitivity should allow for meaningful constraints on the reionization history and astrophysical parameters, especially if FG subtraction techniques can be improved and successfully implemented.
1310.7155
Voids in the SDSS DR9: observations, simulations, and the impact of the survey mask
Sutter, … Weinberg, et al
Find: mask reduces the number density of voids at all scales by factor of 3 and slightly skews the relative size distributions, increases the mean ellipticity by ~30%. Radial density profiles are largely robust to the effects of the mask. No tension with LCDM.
1310.7293
The domination of Saturn's low latitude ionosphere by ring `rain'
O'Donoghue et al
Ionosphere produced when otherwise neutral atmosphere is exposed to a flow of energetic charged particles or solar radiation. At low latitudes, the latter should result in a weak planet-wide glow in IR, corresponding to the planet's uniform illumination by the Sun. The observed low-latitude ionospheric electron density is lower and the temperature higher than predicted by models. A planet-ring magnetic connection has been previously suggested in which an influx of water from the rings could explain the lower than expected electron densities in Saturn's atmosphere. Here, report the detection of a pattern of features, extending across a broad latitude band from ~25 to 60 degrees, that is superposed on the lower latitude background glow, with peaks in emission that map along the planet's B-field lines to gaps in Saturn's rings. This pattern implies the transfer of charged water products from the ring-plane to the ionosphere, revealing they influx on a global scale, flooding between 30 to 43 % of the planet's upper-atompsheric surface. This ring `rain' plays a fundamental role in modulating ionospheric emissions and suppressing electron densities.
1310.7485
Color differences between clockwise and counterclockwise spiral galaxies
Shamir
Clockwise galaxies tend to be bluer than clockwise spiral galaxies. [-2 votes]
1310.7571
The impact of baryonic process on the two-point correlation functions of galaxies, sub haloes and matter
van Daalen, Schaye, … et al
Use large hydro sims to investigate how galaxy formation affects the autocorrelation functions of galaxies, sub haloes, as well as their cross-correlation with matter. Changes due to including baryons not limited to small scales, also present in samples selected by sub halo mass: cluster ~10% more strongly in a baryonic run on scales r~1Mpc/h or larger; difference increases for smaller separations. Inclusion of baryons boosts the clustering at fixed sub halo mass on all scales, the sign of the effect on the cross-correlation of sub haloes with matter can vary with radius. Show: LS effects are due to the cage in sub halo mass caused by the strong feedback associated with galaxy formation and may therefore not affect samples selected by number density. However, on r<r_vir significant differences remain after accounting for the change in sub halo mass. Conclude that predictions for gg and g-mass clustering from models based on DM only sims will have errors greater than 10% on sub-Mpc scales, unless the simulation results are modified to correctly account for the effects of baryons on the distributions of mass and satellites.
1310.7582
Tracing the mass growth and star formation rate evolution of massive galaxies from z~6 to z~1 in the Hubble ultra-feep field
Lundgren van Dokkum, … et al
1500 photo-z galaxies in UDF, 1<z<6; explore the co-evolution of stellar masses and SFR since z~6. SFR steadily increases from z=6 to 3, galaxy number density constant. The peak epoch of SF later for galaxies with increasing number densities, in agreement with cosmic downsizing [I still don't understand this term]. Observed SFR can fully account for the mass growth to z~2 amongst galaxies with cumulative number densities greater than 1e-3.5 Mpc^-3. For lower density galaxies, find observed M* are ~3x greater than which may be accounted for observed SF alone at late times, implying growth from mergers plays win important role at z<2. Observe decreasing sSFR by ~10x from z=6 to 2 with similar densities. The combination of these foundlings can qualitatively explain the previous findings of a sSFR plateau at high z. Trace evolution of the fraction of quiescent galaxies for samples matched in cumulative number density over this z range. Find no unambiguous examples of quiescent galaxies at z>4. [cool!]
1310.7942
Densities and eccentricities of 163 Kepler planets from transit time variations
Hadden, Lithwick
TTVs of 163 sub-Jovian planets, use analytical formula for TTV and find most of these planets have eccentricities of few percent (rms e~0.018pm0.005); planets with R<3R_earth are 3x as eccentric as those with R>3R_earth. Also fit radius-density relation rho ~ 2.2 g/cm^3 x (R/3R_earth)^-1.8 for the 64 planets with small eccentricity (and hence small mass correction). Planets >3R_earth are motley less dense than water, implying that their radii are largely set by a massive H atmosphere.
1310.7948
A uniform metal distribution in the intergalactic medium of the Perseus cluster of galaxies
Werner et al
As the title says. Constant of 0.306pm0.012 Solar out to the edge of the nearby Perseus Cluster. Implies most of the metal enrichment of IGM occurred before the cluster formed, during the maximal SF and BH activity.
1310.8103
Instability windows and evolution of rapidly rotating neutron stars
Gusakov, et al
NS in low mass x-ray binaries (LMXBs) wrt excitation of r-modes. Argue: finite temperature effects in the superfluic core of a NS lead to a resonance coupling and enhanced damping (and hence stability) of oscillation modes at certain stellar temperatures. Demonstrate that NSs with high spin frequency spend a substantial amount of time at these resonance temperatures. Explains hot rapidly rotating NSs in LMXBs, and predict a new class of hot non-accreeting rapidly rotating NSs, some of which may have already been observed and tentatively identified as quiescent LMXB (qLMXB) candidates. Theoretical upper limit on NS spin frequency (~730 Hz), following from statistical analysis of accreting millisecond X-ray pulsars. New tool to constrain superdense matter properties comparing measured and theoretically predicted resonance temperatures.
1310.8298
Tracing the evolution of active galactic nuclei host galaxies over the last 9 Gyrs of cosmic time
Goulding, et al
0<z<1.4 AGN host galaxies in SDSS, Bootes and DEEP2 surveys. ID with X-ray, IR and radio. Radiatively-efficient accretion (X-ray or IR) AGN hosted in separate population than mechanical accretion (radio) AGN. Former appear to preferentially be hosted in modest SF galaxies, with little dependence on AGN or galaxy luminosity. AGN exhibiting radio-emitting jets due to mechanically-dominated accretion are almost exclusively observed in massive, passive galaxies. Strong evidence that the observed host-galaxy trends are independent of redshift. In particular, these different accretion-mode AGN have remained as separate galaxy populations throughout the last 9 Gyr; galaxies hosting AGN appear to have evolved along the same path as galaxies that are not hosting AGN with little evidence for distinctly separation evolution [but I thought AGNs have duty cycles (mostly inactive, with 10% activation rate)?].
1311.0013
The population of giant clumps in simulated high-z galaxies: in-situ and ex-situ, migration and survival
Mandelker, Dekel, .. Primack
AMR cosmo sim study of giant clumps and their radial gradients in high-z disc galaxies. ID clumps by gas density (stellar and DM components considered afterwards). Most over densities are diffuse and elongated, 91% of their mass and 83% of their SFR are in compact round clumps. Almost all galaxies have central, massive bulge clump, 70% of discs show off-center clumps (3-4 per galaxy). Fraction of clumpy disks peaks at intermediate disc masses. Clumps divided into DM content into in-situ and ex-sity, originating from violent disc instability (VDI) and minor mergers, respectively. 60% of the discs are in VDI phase showing off-center in-situ clumps, which contribute 1-7% of the disc mass and 5-45% of its SFR. The in-situ clumps constitute 75% of the off-center clumps in terms of number and SFR but only half the mass, each clump containing on average 1% of the disc mass and 6% of its SFR. The in-situ clumps have young stellar ages, 100-400 Myr, and high sSFR, 1-10 /Gyr. They exhibit certain gradients resulting from inward clump migration, where the inner clumps are somewhat more massive and older, with lower gas fraction and sSFR and higher metallicity. Similar observed gradients indicate that the clumps survive outflows. The ex-situ clumps have stellar ages 0.5-3 Gyr and sSFR 0.1-2 /Gyr, and they exhibit weaker gradients. Massive clumps of old stars at large radii are most likely ex-situ mergers, though half of them share the disc rotation. [Where is the comparison with observation?]
1311.0026
Hydrogen-poor super luminous supernovae and log-duration gamma-ray bursts have similar host galaxies
Lunnan, … Rest, et al
As the title says. The host galaxies of H-poor SLSNe are statistically distinct from the hosts of GOODS core-collapse SNe, but resemble the host galaxies of LGRBs in terms of stellar mass, SFR, sSFR and metallicity. Indicates that the environmental causes leading to massive stars forming either SLSNe or LGRBs are similar, and in particular that SLSNe are more effectively formed in low metallicity environments. Speculate that the key ingredient is large core angular momentum, leading to a rapidly spinning magnetar in SLSNe and an accreting BH in LGRBs.
1311.0057
Spectroscopy of z~7 candidate galaxies: using Lyman-alpha to constrain the neutral fraction of hydrogen in the high-redshift universe
Caruana et al
Target 22 z-band dropouts, find no evidence of Lya emission. May indicate that a significant neutral HI fraction in the IGM suppresses Lya, with an estimated neutral fraction chi_HI~0.5, in agreement with other estimates.
1311.0139
Probing a dark matter density spike at the galactic center
Lacroix, Boehm, Silk
Need to know DM density to estimate DM annihilation amount (seen in gamma-ray and radio fluxes). Use synchrotron emission to probe the DM energy distribution in the inner galaxy. Most crucial assumptions: DM is heavier than a few GeV and directly produces a reasonable amount of e- and e+ in the galaxy. Conclude that DM indirect detection techniques (including the Planck experiment) could be used to shed light on the DM halo profile on scales that lie beyond the capability of any current numerical sims.
1311.0284
The ATLA$^{\rm{3D}}$ project - XXV: Two-dimensional kinematic analysis of simulated galaxies and the cosmological origin of fast and slow rotators
Naab, … et al
In general, major galaxy mergers have a significant influence on the rotation properties resulting win both a sin-down as well as a spin-up of the merger remnant. Lower mass galaxies with significant in-situ formation of stars, or with additional gas-rich major mergers - resulting in a spin-up - in their formation history, form elongated fast rotators with a clear anti-correlation of h3 and v/sigma. Additional formation for fast rotators includes gas poor major mergers leading up to a spin-up of the remnants. This formation path does not result in anti-correlated h3 and v/sigma. The galaxies most consistent with the rare class of non-rotating round early-type galaxy grow by gas-poor minor mergers alone. In general, more massive galaxies have less in-situ SF since z~2, rotate slower and have older stellar populations.
1311.0287
The energy production rate density of cosmic rays in the local universe is $\sim10^{44-45}/rm erg~Mpc^{-3}~yr^{-1}$ at all particle energies
Katx, Waxman, Thompson, Loeb
As the title says. …most exciting possibility is that CRs at all energies are emitted from a single type of (unknown) sources, which cannot be SN remnants.
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