1207.3786
Bounce and cyclic cosmology in extended nonlinear massive gravity
Cai, Gao, Saridakis
Extended nonlinear massive gravity can alter the evolution of the universe at both early and late times.
1207.3793
Cold molecular gas along the cooling X-ray filament in a bell 1795
McDonald, Wei, Veilleux
CO(1-0) observations of cool core (mm-wave). Detect significant amount of cold molecular gas (4e9 Msun) in the central 10 kpc. Discovery of a substantial clump of cold molecular gas at clustercentroic radius of 30 kpc, coincident in both position and velocity with the warm, ionized filaments. Upper limit on the H2 mass at the outer edge of the SF filament (60 kpc distant, <1e9 Msun). Strong gradient in HII/H2 ratio as a function of radius, different ionization mechanisms in the nucleus and filaments. Total mass of cold gas (7e9 Msun) is ~30% of the classical cooling estimate at the same position, assuming 1e9 yr cooling time. Good agreement with the cooling rate of the hot ICM and the mass of the cool gas reservoir suggest that the cooling flow problem stems from a lack of observable cooling in the more diffuse regions at large radii.
1207.3794
Cosmological constraints from the large scale weak lensing of SDSS MaxBCG clusters
Zu, Weinberg, Rozo, Sheldon, Tinker, Becker
Constrain Omega_m (Om) and sigma8 (sig8) from large scale WL (R=5-30 Mpc/h) by clusters in MaxBCG catalog. WL signal proportional to product of Om and xi_cm (cluster mass correlation function). Predicted lensing signal increases with Om or sig8; mild additional dependence on the assumed scatter between richness and mass. Degeneracy broken with dependence of signal on scale and richness. External priors on richness-mass scatter (from x-ray) and shape of MPS P(k) from galaxy clustering. Test adopted model for xi_cm against N-body sims. Use bayesian approach with minimal restrictive priors. Sig8 constraint = 0.82 pm 0.1 and Om = 0.325 pm 0.07 [that's not too great]. Consistent with GR growth and WMAP data. Join constraint is Om=0.29pm0.02 and sig8=0.83pm0.02. Errors dominated by statistical uncertainties of large scale WL measurements, better in future.
* compare with Rachel's paper!
Cosmological constraints from the large scale weak lensing of SDSS MaxBCG clusters
Zu, Weinberg, Rozo, Sheldon, Tinker, Becker
Constrain Omega_m (Om) and sigma8 (sig8) from large scale WL (R=5-30 Mpc/h) by clusters in MaxBCG catalog. WL signal proportional to product of Om and xi_cm (cluster mass correlation function). Predicted lensing signal increases with Om or sig8; mild additional dependence on the assumed scatter between richness and mass. Degeneracy broken with dependence of signal on scale and richness. External priors on richness-mass scatter (from x-ray) and shape of MPS P(k) from galaxy clustering. Test adopted model for xi_cm against N-body sims. Use bayesian approach with minimal restrictive priors. Sig8 constraint = 0.82 pm 0.1 and Om = 0.325 pm 0.07 [that's not too great]. Consistent with GR growth and WMAP data. Join constraint is Om=0.29pm0.02 and sig8=0.83pm0.02. Errors dominated by statistical uncertainties of large scale WL measurements, better in future.
* compare with Rachel's paper!
1207.2795
3D-HST grism spectrosocpy of a gravitationally lensed, low-metallicity starburst galaxy at z=1.847
Brammer, .... van Dokkum et al
HST imaging and spectroscopy of a cusp-arc lensed galaxy at z=1.847. UV continuum blue, but optically red. Source of this discrepancy is the extremely strong OIII 5007 and H-beta emission lines with rest-frame EWs of 2000 and 520 AA. sSFR~100/Gyr, M*~1e8 Msun, metallicity log(O/H) = 7.5 - 12. Compare with local blue compact dwarf analogs; simiar in UV/optical SED, spatial morphology and emission line equivalent widths and ratios; upturn at mid-IR wavelengths from hot dust heated by starbursts. Spectra spatially resolved; two clumps with combined size r_e~300pc, resolve differences in UV color and EW between them. This is a low-metallicity star-bursting dwarf galaxy (not AGN). Lots of this kind should be found in 3d-HST grism survey.
1207.3797
The Apache Point Observatory Glactic Evolution Experiment: first detection of high velocity milky way bar stars
Nidever ... Schneider (Don), et al
From APOGEE (SDSS III) found radial velocities for 4700 K/M-giant stars in MW bulge. A largest spec sample of giant stars in this region of the galaxy. A cold (sigma_v~30 km/s), high-velocity peak (V_GSR~200 km/s) is found to comprise a significant fraction (~10%) of stars in many of the 18 fields. This high RVs not expected for a simple, circularly rotating disk. Not from Sagittarius tidal stream or a new stream in MW disk (preliminary study). These high RVs are best explained by stars in orbits of the Galactic bar potential, although some features remain unexplained.
1207.3799
Colors of dynamically associated asteroid pairs
Moskovitz
(1) components of observed pair systems have the same colors, and (2) color distirbution of asteroid pairs appears indistinguishable from all Main Belt asteroids. Supports pair formation with a common progenitor, and pair formation is likely a compositionally independent process. Binary disruption and/or rotational fission.
1207.3812
How to nurture scientific discoveries despite their unpredictable nature
Loeb
You'd think that it's not possible to artificially cultivate an environment discoveries, because major discoveries are not predictable. But an open research without a programmatic agenda establishes a fertile ground for unexpected breakthroughs. Funding agencies should allocate a small fraction of their funds to support research centers of excellence without programmatic reins tied to specific goals.
1207.3814
Thermal instabilities in cooling galactic coronae: fuelling star formation in galactic disks
Hobs, Read, Power, Cole
Means by which cold gas can accrete onto MW mass galaxies from a hot corona of gas. Cold clumps seen in many classic SPH simulations are not present in SPHS simulations; classic SPH cold clumps owe to a numerical thermal instability caused by inability for cold gas to mix with hot halo. New simulation show cold filaments break up into bound clumps that form into stars. Filaments are overdense by a factor of 10-100 compared to surrounding gas; fragmentation results from a physical NL instability driven by the overdensity. Fragmenting filament mode of disk growth affects role of SF in brining cold gas into disk galaxies.
1207.3856
Sub-millimetre galaxies in cosmological hydrodynamic simulations: source number counts and the spatial clustering
Shimizu, Yoshida, Okamoto
Use SPH to study the formation and evolution of SMGs. Generate model, predict source number counts and clustering amplitude.
1207.3879
Probing pre-galactic metal enrichment with high-redshift gamma-ray bursts
Wang, Bromm, Greif, Stacy, Dai, Loeb, Cheng
Explore high-z GRBs as tools to probe pre-galactic metal enrichment. Afterglow of a Pop III GRB in a primordial dwarf galaxy as a luminous BG source; calculate the strength of metal absorption lines imprinted by the first heavy elements in the IGM. Use simulation of first galaxy, halo virial temperature of >1e4 K. GRBs have high luminosity and featureless power-law spectra, making it an ideal tool. The metals in the first galaxies produced by the first SN are likely to reside in low-ionization stages. Show: if afterglow observed sufficiently eraly, analysis of the metal lines can distinguish whether the first heavy elements were produced in a PISN or a core-collapse (Type II) SN, thus constraining the IMF of the first stars.
* what's a PISN?
1207.3924
Gas depletion in cluster galaxies depends strongly on their internal structure
Zhang, Li, Kauffmann, Xiao
Photometric gas mass indicator in 300 nearby groups: estimate the degree to which the ISM of a cluster galaxy has been depleted. Low density galaxies more easily depleted of their gas, has less to do with cluster-centric distance.
1207.3928
Qualitative interpretation of galaxy spectra
Almeida et al
Qualitative interpretation of galaxy spectra, for quick-look analysis, gain physical insight. Developed for understanding the nature of the automatic spectroscopic K-mans based (ASK) template spectra. Resulted from classification of galaxy spectra in SDSS DR7. ... Old stars are metal rich or metal poor depending on whether they reside in passive galaxies or in star-forming galaxies.
1207.3969
Warm H2O and OH in the disk around the Herbig star HD 163296
* Herbig Ae/Be star (HABe): pre-MS star, young (< 10Myr) of spectral types A or B, still embedded in gas-dust envelopes, and may be surrounded by circumstellar disks. H and Ca lines observed in their spectra. 2-8 Msun objects, not burning H at the center yet. Sometimes show significant brightness variability, probably due to clumps in circumstellar disk. In the lowest brightness stage, the radiation from the star becomes bluer and linearly polarized (disk-scatter light). Analogs in the smaller mass range are called T Tauri stars. >8Msun protostars not observed, because they evolve quickly (by the time they are observed, they are already burning H in the core).
As the title says.
1207.4032
Relative orientation of pairs of spiral galaxies in the Sloan digital sky survey
Buxton, Ryden
Study of binary spiral galaxies in SDSS DR6 find that the relative orientation of disks in binary spiral galaxies is consistent with their being drawn from random distribution of orientations. 747 isolated pairs of luminous disk galaxies studied. The distribution of the angle between the major axies of the galaxy images consistent with uniform distribution.
1207.4061
Planck Intermediate results. V. Pressure profiles of galaxy clusters from the Sunyaev-Zeldovich effect
Planck Collaboration
Pressure profiles of 62 nearby massive clusters at high S/N. Most clusters are individually detected at least out to R500. Stack radial profiles to get profile out to 3xR500; dispersion about the mean profile dominates the statistical errors across the whole radial range. Measurement fully consistent earlier Planck integrated flux, which is consistent with X-ray inside R500. Correct profile for the effects of Planck beam.
[Wed **/53]
1207.3683
On the nature and detectability of Type Ib/c supernova progenitors
Yoon, et al
* Wolf-Rayet stars: evolved, massive stars (>20 Msun) which are losing mass rapidly by means of very strong stellar wind (up to 2000 km/s). Typically loses 1e-5 Msun/yr. Extremely hot (30kK to 200kK) and highly luminous, mostly in FUV and soft X-rays.
The progenitors should be WR stars, but survey search unsuccessful. At pre-SN stage, they are visually faint, despite their high bolometric luminosities, compared to bulk of WR stars. SNe Ibc observations have so far not provided strong constraints on progenitor bolometric luminosities and masses. Ic progenitors more challenging to identify than Ib in optical.
1207.3720
Astrophysical applications of gravitational microlensing
Mao
(1) u-lensing towards MCs rule out MW halo dominated by MACHOs---most DM are non-baryonic. (2) discovery of 20 extrasolar planets (16 published)---test core accreetion theory of planet formation. (3) measure the mass of isolated stars (brown dwarfs to normal stars) (4) high-res, ToO spectra of highly-magnified dwarf stars---hint at enhanced He enrichment or unusual bulge formation theories (5) limb-darkening profiles measured for ~10 giant stars, challenges stellar atmosphere models. (6) strong constraints on the geometry and kinematics of MW bar (through proper motions).
3D-HST grism spectrosocpy of a gravitationally lensed, low-metallicity starburst galaxy at z=1.847
Brammer, .... van Dokkum et al
HST imaging and spectroscopy of a cusp-arc lensed galaxy at z=1.847. UV continuum blue, but optically red. Source of this discrepancy is the extremely strong OIII 5007 and H-beta emission lines with rest-frame EWs of 2000 and 520 AA. sSFR~100/Gyr, M*~1e8 Msun, metallicity log(O/H) = 7.5 - 12. Compare with local blue compact dwarf analogs; simiar in UV/optical SED, spatial morphology and emission line equivalent widths and ratios; upturn at mid-IR wavelengths from hot dust heated by starbursts. Spectra spatially resolved; two clumps with combined size r_e~300pc, resolve differences in UV color and EW between them. This is a low-metallicity star-bursting dwarf galaxy (not AGN). Lots of this kind should be found in 3d-HST grism survey.
1207.3797
The Apache Point Observatory Glactic Evolution Experiment: first detection of high velocity milky way bar stars
Nidever ... Schneider (Don), et al
From APOGEE (SDSS III) found radial velocities for 4700 K/M-giant stars in MW bulge. A largest spec sample of giant stars in this region of the galaxy. A cold (sigma_v~30 km/s), high-velocity peak (V_GSR~200 km/s) is found to comprise a significant fraction (~10%) of stars in many of the 18 fields. This high RVs not expected for a simple, circularly rotating disk. Not from Sagittarius tidal stream or a new stream in MW disk (preliminary study). These high RVs are best explained by stars in orbits of the Galactic bar potential, although some features remain unexplained.
1207.3799
Colors of dynamically associated asteroid pairs
Moskovitz
(1) components of observed pair systems have the same colors, and (2) color distirbution of asteroid pairs appears indistinguishable from all Main Belt asteroids. Supports pair formation with a common progenitor, and pair formation is likely a compositionally independent process. Binary disruption and/or rotational fission.
1207.3812
How to nurture scientific discoveries despite their unpredictable nature
Loeb
You'd think that it's not possible to artificially cultivate an environment discoveries, because major discoveries are not predictable. But an open research without a programmatic agenda establishes a fertile ground for unexpected breakthroughs. Funding agencies should allocate a small fraction of their funds to support research centers of excellence without programmatic reins tied to specific goals.
1207.3814
Thermal instabilities in cooling galactic coronae: fuelling star formation in galactic disks
Hobs, Read, Power, Cole
Means by which cold gas can accrete onto MW mass galaxies from a hot corona of gas. Cold clumps seen in many classic SPH simulations are not present in SPHS simulations; classic SPH cold clumps owe to a numerical thermal instability caused by inability for cold gas to mix with hot halo. New simulation show cold filaments break up into bound clumps that form into stars. Filaments are overdense by a factor of 10-100 compared to surrounding gas; fragmentation results from a physical NL instability driven by the overdensity. Fragmenting filament mode of disk growth affects role of SF in brining cold gas into disk galaxies.
1207.3856
Sub-millimetre galaxies in cosmological hydrodynamic simulations: source number counts and the spatial clustering
Shimizu, Yoshida, Okamoto
Use SPH to study the formation and evolution of SMGs. Generate model, predict source number counts and clustering amplitude.
1207.3879
Probing pre-galactic metal enrichment with high-redshift gamma-ray bursts
Wang, Bromm, Greif, Stacy, Dai, Loeb, Cheng
Explore high-z GRBs as tools to probe pre-galactic metal enrichment. Afterglow of a Pop III GRB in a primordial dwarf galaxy as a luminous BG source; calculate the strength of metal absorption lines imprinted by the first heavy elements in the IGM. Use simulation of first galaxy, halo virial temperature of >1e4 K. GRBs have high luminosity and featureless power-law spectra, making it an ideal tool. The metals in the first galaxies produced by the first SN are likely to reside in low-ionization stages. Show: if afterglow observed sufficiently eraly, analysis of the metal lines can distinguish whether the first heavy elements were produced in a PISN or a core-collapse (Type II) SN, thus constraining the IMF of the first stars.
* what's a PISN?
1207.3924
Gas depletion in cluster galaxies depends strongly on their internal structure
Zhang, Li, Kauffmann, Xiao
Photometric gas mass indicator in 300 nearby groups: estimate the degree to which the ISM of a cluster galaxy has been depleted. Low density galaxies more easily depleted of their gas, has less to do with cluster-centric distance.
1207.3928
Qualitative interpretation of galaxy spectra
Almeida et al
Qualitative interpretation of galaxy spectra, for quick-look analysis, gain physical insight. Developed for understanding the nature of the automatic spectroscopic K-mans based (ASK) template spectra. Resulted from classification of galaxy spectra in SDSS DR7. ... Old stars are metal rich or metal poor depending on whether they reside in passive galaxies or in star-forming galaxies.
1207.3969
Warm H2O and OH in the disk around the Herbig star HD 163296
* Herbig Ae/Be star (HABe): pre-MS star, young (< 10Myr) of spectral types A or B, still embedded in gas-dust envelopes, and may be surrounded by circumstellar disks. H and Ca lines observed in their spectra. 2-8 Msun objects, not burning H at the center yet. Sometimes show significant brightness variability, probably due to clumps in circumstellar disk. In the lowest brightness stage, the radiation from the star becomes bluer and linearly polarized (disk-scatter light). Analogs in the smaller mass range are called T Tauri stars. >8Msun protostars not observed, because they evolve quickly (by the time they are observed, they are already burning H in the core).
As the title says.
1207.4032
Relative orientation of pairs of spiral galaxies in the Sloan digital sky survey
Buxton, Ryden
Study of binary spiral galaxies in SDSS DR6 find that the relative orientation of disks in binary spiral galaxies is consistent with their being drawn from random distribution of orientations. 747 isolated pairs of luminous disk galaxies studied. The distribution of the angle between the major axies of the galaxy images consistent with uniform distribution.
1207.4061
Planck Intermediate results. V. Pressure profiles of galaxy clusters from the Sunyaev-Zeldovich effect
Planck Collaboration
Pressure profiles of 62 nearby massive clusters at high S/N. Most clusters are individually detected at least out to R500. Stack radial profiles to get profile out to 3xR500; dispersion about the mean profile dominates the statistical errors across the whole radial range. Measurement fully consistent earlier Planck integrated flux, which is consistent with X-ray inside R500. Correct profile for the effects of Planck beam.
[Wed **/53]
1207.3683
On the nature and detectability of Type Ib/c supernova progenitors
Yoon, et al
* Wolf-Rayet stars: evolved, massive stars (>20 Msun) which are losing mass rapidly by means of very strong stellar wind (up to 2000 km/s). Typically loses 1e-5 Msun/yr. Extremely hot (30kK to 200kK) and highly luminous, mostly in FUV and soft X-rays.
The progenitors should be WR stars, but survey search unsuccessful. At pre-SN stage, they are visually faint, despite their high bolometric luminosities, compared to bulk of WR stars. SNe Ibc observations have so far not provided strong constraints on progenitor bolometric luminosities and masses. Ic progenitors more challenging to identify than Ib in optical.
1207.3720
Astrophysical applications of gravitational microlensing
Mao
(1) u-lensing towards MCs rule out MW halo dominated by MACHOs---most DM are non-baryonic. (2) discovery of 20 extrasolar planets (16 published)---test core accreetion theory of planet formation. (3) measure the mass of isolated stars (brown dwarfs to normal stars) (4) high-res, ToO spectra of highly-magnified dwarf stars---hint at enhanced He enrichment or unusual bulge formation theories (5) limb-darkening profiles measured for ~10 giant stars, challenges stellar atmosphere models. (6) strong constraints on the geometry and kinematics of MW bar (through proper motions).
[Tue **/47]
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