1110.5903
Andromeda XXVIII: A dwarf galaxy more than 350 kpc from Andromeda
Slater, Bell, Martin
Discovery of a new dwarf galaxy, Andromeda-the-28th, using data from SDSS DR8, at distance 365 kpc separation. 650kpc away from the sun, absolute magnitude of M_V=-8.5, half-light radius of r_h=210 pc (similar to may other faint Local Group dwarfs). Unable to determine whether star formation is going on, so don't know if it's a dwarf spheroidal or dwarf irregular.
1110.5904
Optical line emission in brightest cluster galaxies at 0<z<0.6: evidence for a lack of strong cool cores 3.5 Gyr ago?
McDonald
* Perseus A (NGC1275, Caldwell 24): a type 1.5 Seyfert galaxy located ~70 Mpc away. BCG of the Perseus Cluster of galaxies. Morphologically a type-cD galaxy. Contains a massive network of spectral line emitting filaments--dragged out by rising bubbles of relativistic plasma generated by the central AGN. Gas filaments are cooler than the surrounding intergalactic cloud--how do they persist? How come it hasn't collapsed to form stars? Possibly magnetic fields.
* cD galaxy: a subtype of type-D giant elliptical galaxy, which has a large halo of stars. Found near the centers of some rich galaxy clusters. ("central dominant galaxies", "supergiant ellipticals")
>30,000 optically-detected galaxy clusters in the range 0<z<0.6: combine these catalogs with the availability of optical spectroscopy of the brightest cluster galaxy from SDSS allows for the observation of evolution of optical line emission in BCGs over this redshift range. A minimum fraction of BCGs with optical line emission is found at z~0.3, suggesting that complex, filamentary emission in systems (e.g. Perseus A) are a recent phenomenon. Evidence for an upturn in the number of strongly-emitting systems is reported beyond z>0.3, hinting at an earlier epoch of strong cooling. Compare evolution of emission line nebulae to the X-ray derived cool core fraction from the literature, and find overall agreement, with the exception that an upturn in strong CC fraction is not observed at z>0.3. Overall agreement between the evolution of cool cores and optical line emission at low redshift suggests that emission-line surveys of galaxy clusters may provide an efficient method of indirectly probing the evolution of cool cores, and provide insights into the balance of heating and cooling processes at early cosmic times.
* but what about the "disagreement" at z>0.3, where line emission gets stronger, but CC fraction doesn't rise? Isn't there concern that emission line do not necessarily correlate to existence of CC?
1110.5904
Optical line emission in brightest cluster galaxies at 0<z<0.6: evidence for a lack of strong cool cores 3.5 Gyr ago?
McDonald
* Perseus A (NGC1275, Caldwell 24): a type 1.5 Seyfert galaxy located ~70 Mpc away. BCG of the Perseus Cluster of galaxies. Morphologically a type-cD galaxy. Contains a massive network of spectral line emitting filaments--dragged out by rising bubbles of relativistic plasma generated by the central AGN. Gas filaments are cooler than the surrounding intergalactic cloud--how do they persist? How come it hasn't collapsed to form stars? Possibly magnetic fields.
* cD galaxy: a subtype of type-D giant elliptical galaxy, which has a large halo of stars. Found near the centers of some rich galaxy clusters. ("central dominant galaxies", "supergiant ellipticals")
>30,000 optically-detected galaxy clusters in the range 0<z<0.6: combine these catalogs with the availability of optical spectroscopy of the brightest cluster galaxy from SDSS allows for the observation of evolution of optical line emission in BCGs over this redshift range. A minimum fraction of BCGs with optical line emission is found at z~0.3, suggesting that complex, filamentary emission in systems (e.g. Perseus A) are a recent phenomenon. Evidence for an upturn in the number of strongly-emitting systems is reported beyond z>0.3, hinting at an earlier epoch of strong cooling. Compare evolution of emission line nebulae to the X-ray derived cool core fraction from the literature, and find overall agreement, with the exception that an upturn in strong CC fraction is not observed at z>0.3. Overall agreement between the evolution of cool cores and optical line emission at low redshift suggests that emission-line surveys of galaxy clusters may provide an efficient method of indirectly probing the evolution of cool cores, and provide insights into the balance of heating and cooling processes at early cosmic times.
* but what about the "disagreement" at z>0.3, where line emission gets stronger, but CC fraction doesn't rise? Isn't there concern that emission line do not necessarily correlate to existence of CC?
1110.5906
Andromeda XXIX: A new dwarf spheroidal galaxy 200kpc from Andromeda
Bell, Slater, Martin
Discovery of Andromeda-the-29th from SDSS DR8, and confirmed by Gemini North MOS imaging data, appears to be a dwarf spheroidal. Sky separation is >15 degrees from M31, red-branch tip distance estimate of 730kpc (from the Sun), corresponding to 200kpc distance from M31, it's virial radius. Absolute magnitude determined by comparison to Draco dwarf spheroidal is M_V=-8.3. The XXIX's stellar populations appear very similar to Draco's; estimate metallicity for And XXIX of [Fe/H]~-1.8. Half-light radius is 360pc, and its ellipticty is 0.35, typical of dwarf satellites of the MW and M31 at this magnitude range.
Andromeda XXIX: A new dwarf spheroidal galaxy 200kpc from Andromeda
Bell, Slater, Martin
Discovery of Andromeda-the-29th from SDSS DR8, and confirmed by Gemini North MOS imaging data, appears to be a dwarf spheroidal. Sky separation is >15 degrees from M31, red-branch tip distance estimate of 730kpc (from the Sun), corresponding to 200kpc distance from M31, it's virial radius. Absolute magnitude determined by comparison to Draco dwarf spheroidal is M_V=-8.3. The XXIX's stellar populations appear very similar to Draco's; estimate metallicity for And XXIX of [Fe/H]~-1.8. Half-light radius is 360pc, and its ellipticty is 0.35, typical of dwarf satellites of the MW and M31 at this magnitude range.
1110.5910
The clustering of X-ray selected AGN at z=0.1
Mountrichas, Georgakakis
Select AGNs at z~0.1 from XMM on SDSS, and cross correlate with the SDSS Main galaxy sample; inferred X-ray AGN auto-correlation function described by a power law with slope gamma~2.0. Corresponding mass of the DM haloes that host X-ray AGN at z~0.1 is 1e13 Msun/h. Comparison with high-z show that this mass scale is characteristic of moderate luminosity X-ray AGN out to z~1. Split AGN sample by rest-frame color shows that X-ray sources in red hosts are more clustered than those associated with blue galaxies, in agreement with results at z~1. Find host galaxies of X-ray AGN have lower stellar masses compared ot the typical central galaxy of a ~1e13Msun/h DM halo. AGN hosts either have experienced less stellar mass growth compared to the average central galaxy of this halo mass, or a fraction of them are associated with satellite galaxies.
* taking correlation function of AGN is useful for galaxy physics, but not so much for cosmology, I think.
1110.5913
Dense gas without star formation: the kpc-sized molecular disk in 3C326N
Nesvabda, Boulanger, Lehnert, Guillard, Salome
Discovery of 3kpc disk of 1e9 Ms [???] of dense, warm H2 in the nearby radio galaxy 3C326 N, which shows no signs of on-going or recent star formation and falls a factor of 60 below the Schmidt-Kennicutt law. Spectroscopy show ro-vibrational H2 lines across all of the disk, with irregular profiles and line ratios consistent with shocks. Gas is highly turbulent and not gravitationally bound. If Jet absent, then SF should be happening. Rapid H2 formation boosted by turbulent compression deemed possible with hydrosims, so propose that molecules formed from diffuse atomic gas in the turbulent jet cocoon. Gas is not self-gravitating, so cannot form molecular clouds or stars while the jet is active, and is likely to disperse and become atomic again after the nuclear activity ceases. [why? because it's too hot? once it's a molecule, what makes them become atomic again?] Speculate that very low star-formation rates are to be expected under such conditions, provided that large-scale turbulence sets the gas dynamics in molecular clouds. Results illustrate that jets may create large molecular reservours as expected in 'positive feedback' scenarios of AGN-triggered star formation, but that this alone is not sufficient to trigger star formation.
1110.5919
Asymmetric dark matter may alter the evolution of low-mass stars and brown dwarfs
Zentner, Hearin
Theories of stellar interiors with puddles of 4~10 GeV DM particles.
1110.5920
Locations of satellite galaxies in the Two-degree field galaxy redshift survey
Agustsson, Brainered
Compute locations of satellite galaxies in 2dF using 2 selection criteria and 3 sources of photometric data. Find satellites are located preferentially near the major axes of their hosts, and the anisotropy is detected at a highly significant level. Locations of satellites that have high velocities relative to their hosts are statistically indistinguishable from locations of satellites that have low velocities relative to their hosts. [why is this important?] Satellites with passive star formation [what does this mean?] are distributed anisotropically about their hosts, while the locations of SF satellites are consistent with an isotropic distribution. These two distributions are, however, statistically indistinguishable [gah].
The clustering of X-ray selected AGN at z=0.1
Mountrichas, Georgakakis
Select AGNs at z~0.1 from XMM on SDSS, and cross correlate with the SDSS Main galaxy sample; inferred X-ray AGN auto-correlation function described by a power law with slope gamma~2.0. Corresponding mass of the DM haloes that host X-ray AGN at z~0.1 is 1e13 Msun/h. Comparison with high-z show that this mass scale is characteristic of moderate luminosity X-ray AGN out to z~1. Split AGN sample by rest-frame color shows that X-ray sources in red hosts are more clustered than those associated with blue galaxies, in agreement with results at z~1. Find host galaxies of X-ray AGN have lower stellar masses compared ot the typical central galaxy of a ~1e13Msun/h DM halo. AGN hosts either have experienced less stellar mass growth compared to the average central galaxy of this halo mass, or a fraction of them are associated with satellite galaxies.
* taking correlation function of AGN is useful for galaxy physics, but not so much for cosmology, I think.
1110.5913
Dense gas without star formation: the kpc-sized molecular disk in 3C326N
Nesvabda, Boulanger, Lehnert, Guillard, Salome
Discovery of 3kpc disk of 1e9 Ms [???] of dense, warm H2 in the nearby radio galaxy 3C326 N, which shows no signs of on-going or recent star formation and falls a factor of 60 below the Schmidt-Kennicutt law. Spectroscopy show ro-vibrational H2 lines across all of the disk, with irregular profiles and line ratios consistent with shocks. Gas is highly turbulent and not gravitationally bound. If Jet absent, then SF should be happening. Rapid H2 formation boosted by turbulent compression deemed possible with hydrosims, so propose that molecules formed from diffuse atomic gas in the turbulent jet cocoon. Gas is not self-gravitating, so cannot form molecular clouds or stars while the jet is active, and is likely to disperse and become atomic again after the nuclear activity ceases. [why? because it's too hot? once it's a molecule, what makes them become atomic again?] Speculate that very low star-formation rates are to be expected under such conditions, provided that large-scale turbulence sets the gas dynamics in molecular clouds. Results illustrate that jets may create large molecular reservours as expected in 'positive feedback' scenarios of AGN-triggered star formation, but that this alone is not sufficient to trigger star formation.
1110.5919
Asymmetric dark matter may alter the evolution of low-mass stars and brown dwarfs
Zentner, Hearin
Theories of stellar interiors with puddles of 4~10 GeV DM particles.
1110.5920
Locations of satellite galaxies in the Two-degree field galaxy redshift survey
Agustsson, Brainered
Compute locations of satellite galaxies in 2dF using 2 selection criteria and 3 sources of photometric data. Find satellites are located preferentially near the major axes of their hosts, and the anisotropy is detected at a highly significant level. Locations of satellites that have high velocities relative to their hosts are statistically indistinguishable from locations of satellites that have low velocities relative to their hosts. [why is this important?] Satellites with passive star formation [what does this mean?] are distributed anisotropically about their hosts, while the locations of SF satellites are consistent with an isotropic distribution. These two distributions are, however, statistically indistinguishable [gah].
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