1201.4171
Studying the asymmetry of the GC population of NGC 4261
Bonfinit, Zezas, Birkinshaw, Worrall, Fabbiano, O'Sullivan, Trinchieri, Wolter
Red GCs have radial distribution steeper than the galaxy surface brightness, the blue subpopulation is consistent. The significant asymmetry of the GC population about a NE-SW direction and the lack of any obvious feature in the morphology of the galaxy suggests that the asymmetry could be the result of an interaction of a merger.
1201.4175
Examining the radio-loud/radio-quiet dichotomy with new Chandra and VLA observations of 13 UGC galaxies
Kharb, et al
Explore the connection between the host galaxies and AGN activity in a radio-selected sample: detect nuclear x-ray emission in 8 sources, and radio emission in all but one. Presence of nuclear radio sources in 12 of the 13 galaxies confirms the AGN nature. Behaviour of the x-ray and radio emission in these sources depend on the form of their optical surface brightness profiles derived from HST imaging ("core", "power-law", or "intermediate" galaxies). Find: more than twice the number of "power-law" and "intermediate" galaxies lie well above the radio-x-ray correlation established in FRI radio galaxies and the low luminosity "core" galaxies. Results highlights the fact that the "radio-loud/radio-quiet" dichotomy is a function of the host galaxy's optical surface brightness profile [??]. Present radio-optical X-ray spectral indicies of 51 sample galaxies. Survival statistics point to significant differences in the radio-to-optical and radio-to-x-ray spectral indicies ...
* FR I radio galaxies (cored)
* FR II radio galaxies (lobed)
1201.4186
What sets the initial rotation rates of massive stars?
Rosen, Krumholz, Ramirez-Ruiz
Physical mechanisms that set the initial rotation rates in massive stars are unknown in current star formation theory. The magnetic coupling between a star and its accretion disk may be sufficient to spin down low-mass pre-main sequence (PMS) stars to well below breakup at the end stage of their formation when the accretion rate is low. However, show that the magnetic torques are insufficient to spin down massive PMS stars due to their short formation times and high accretion rates. Develop a model for the angular momentum evolution of stars over a wide range in mass, considering both magnetic and gravitational torques. Find magnetic torques are unable to spin down either low or high mass stars during the main accretion phase and that massive stars cannot be spun down significantly by magnetic torques during the end stage of their formation either. Spin-down occurs only if massive stars disk lifetimes are substantially longer of their magnetic fields are much stronger than current observations suggest.
1201.4190
Outliers in the 0Z survey
Cohen, et al
Abundance analysis of more than 100 candidate stars of extremely metal-poor stars with [Fe/H]<-3.0 dex. 57 match criteria, 18 are below -3.3. Ignore C enhancement which can vary, there are 0 to 3 strong outliers for abundance ratio tested from Mg to Ni. ...
1201.4204
New Observational evidence of flash mixing on the WD cooling curve
Brown, Lanz, Sweigart, Cracraft, Hubeny, Landsman
Blue hook stars: class of subluminous extreme horizontal branch stars discovered in UV images of massive globular clusters omega Cen and NGC 2808; occupy region of the HR diagram that is unexplained by canonical stellar evolution theory. New models (evolutionary and atmospheric), show that the blue hook stars are very likely the progeny of stars that undergo extensive internal mixing during a late helium-core flash on the WD cooling curve. This "flash mixing" produces hotter-than-normal EHB stars with atmospheres significantly enhanced in He and C. Large bolometric correction combined with the decrease in H opacity makes these stars appear subluminous in the optical and UV. Flash mixling is more likely to occur in stars born with a high He abundance, due to their lower mass at the main sequence turnoff. The phenomenon is more common in those massive globular clusters that show evidence for secondary populations enhanced in He. However, a high He abundance does not, by itself, explain the presence of blue hook stars in massive globular clusters. Present new observational evidence for flash mixing using HST observations: UV color-magnitude diagrams of six massive globular clusters and far-UV spectroscopy of hot subdwarfs.
1201.4240
Testing the AGN unification model in the IR
Almeida, et al
* Seyfert galaxies: class of galaxies with nuclei that produce spectral line emission from highly ionized gas.
Present near-to-mid IR SEDs for 21 Seyfert galaxies using subarcsecond resolution imaging data. Aim: compare properties of Sy1 and Sy2 tori using clumpy torus models and a Bayesian approach to fit the IR nuclear SEDs. These dusty tori have physical sizes smaller than 6pc radius. Find evidence that strong unification may not hold; immediate dusty surroundings of Sy1 and Sy2 nuclei are intrinsically different. Type 2 tori studied are broader, have more clumps, and these clumps have lower optical depths than those of Type 1 tori. Larger the covering factor of the torus, the smaller the probability of having direct view of the AGN, and vice-versa. In the sample, Sy2 tori have larger covering factors (C_T=0.95 pm 0.02) and smaller escape probabilities than those of Sy1. On the basis of results presented here, the classification of a Seyfert galaxy may depend more on the intrinsic properties of the torus rather than on its mere inclination, in contradiction with the simplest unification model.
1201.4266
Radio-optical outlier quasars - a case study with ICRF2 and SDSS
Orosz, Frey
Find that DR7 astrometry is better than DR8, when compared to radio sources. The optical-to-radio offset may be due to dual AGN, etc.
1201.3920
AGN clustering in the X-ray band
Cappelluti, Allevato, Finoguenov
Review from 1988 to 2011 on X-ray clustering: First: clustering of CXB sources resembles that of optical QSO, then X-ray AGN are hosted by DM haloes of mass similar to that of galaxy groups; hypothesis of galaxy mergers constitute the main AGN triggering mechanism. However detailed analysis of observational data, acquired with modern telescopes along with the HOD models revealed that the triggering of an AGN could also be attributed to phenomena like tidal disruption or disk instability, and to galaxy evolution.
1201.3936
Globular cluster luminosity function as distance indicator
Rejkuba
Globular clusters: Differential magnitude distribution of old globular clusters is very similar in different galaxies presenting a peak at M_V~-7.5. This peak magnitude of the globular cluster luminosity function has been established as a secondary distance indicator. Intrinsic accuracy: ~0.2 mag. Recent results: show distance indicator depends on complex physics of the cluster formation and dynamical evolution, and can have dependencies on Hubble type [?], environment and dynamical history of the host galaxy. Corrections are often relatively small.
1201.3942
Dark Matter: a brief review
Peter
Review the current status of the search for the nature of dark matter. Provide an introduction to possible particle candidates for DM and highlight recent experimental astroparticle- and particle-physics results that constrain the properties of those candidates. Given the absence of detections in those experiments, advocate a return of the problem of DM identification to astronomy, and show what kinds of theoretical and observational work might be used to pin down the nature of DM once and for all. Intended for a broad astronomy audience.
1201.3989
The HST cluster SNe survey: III. correlated properties of types Ia SNe and their hosts at 0.9<z<1.46
Meyers, Aldering, Barbary, ... Dawson, ... Faccioli, Fakhouri, ... Gladders, Goldhaber, .. et al
Search for correlations between the properties of SNe and their host galaxies at high z. Use galaxy color and quantitative morphology to determine the red sequence in 25 clusters and develop a model to distinguish passively evolving early-type galaxies from SF galaxies in both clusters and the field. Identify 6 SN Ia hosts that are early-type cluster members and 11 SN Ia hosts that are early-type field galaxies. Confirm for the first time at z>0.9 that SNe Ia hosted by early-type galaxies brighten and fade more quickly than SN Ia hosted by late-type galaxies. Also show that the two samples of hosts produce SNe Ia with similar color distributions. Thow samples of hosts produce SNe Ia with similar color distributions. The relatively simple SEDs expected for passive galaxies enable measurement of stellar masses of early-type SN hosts. Combine with SM estimates of late-type GOODS SN hosts, investigate the correlation of host mass with Hubble residual observed at lower redshifts (sample small and uncertainties large). A hint of this relation found at z>0.9. Simultaneously fit the average cluster galaxy formation history and dust content to the red-sequence scatters: show that the reddening of early-type cluster SN hosts is likely E(B-V)<0.06. Similarity of the field and cluster early-type host samples suggests that field early-type galaxies that lie on the red sequence may also be minimally affected by dust. The early-type hosted SNeIa studied occupy a more favorable environment to use as well-characterized high-z standard candles than other SNIa.
1201.4011
Solar diameter with 2012 Venus transit
Sigismondi
Measure the diameter of the Sun better than 0.01 arcsec. Infer luminosity from size; compare with past values.
Outliers in the 0Z survey
Cohen, et al
Abundance analysis of more than 100 candidate stars of extremely metal-poor stars with [Fe/H]<-3.0 dex. 57 match criteria, 18 are below -3.3. Ignore C enhancement which can vary, there are 0 to 3 strong outliers for abundance ratio tested from Mg to Ni. ...
1201.4204
New Observational evidence of flash mixing on the WD cooling curve
Brown, Lanz, Sweigart, Cracraft, Hubeny, Landsman
Blue hook stars: class of subluminous extreme horizontal branch stars discovered in UV images of massive globular clusters omega Cen and NGC 2808; occupy region of the HR diagram that is unexplained by canonical stellar evolution theory. New models (evolutionary and atmospheric), show that the blue hook stars are very likely the progeny of stars that undergo extensive internal mixing during a late helium-core flash on the WD cooling curve. This "flash mixing" produces hotter-than-normal EHB stars with atmospheres significantly enhanced in He and C. Large bolometric correction combined with the decrease in H opacity makes these stars appear subluminous in the optical and UV. Flash mixling is more likely to occur in stars born with a high He abundance, due to their lower mass at the main sequence turnoff. The phenomenon is more common in those massive globular clusters that show evidence for secondary populations enhanced in He. However, a high He abundance does not, by itself, explain the presence of blue hook stars in massive globular clusters. Present new observational evidence for flash mixing using HST observations: UV color-magnitude diagrams of six massive globular clusters and far-UV spectroscopy of hot subdwarfs.
1201.4240
Testing the AGN unification model in the IR
Almeida, et al
* Seyfert galaxies: class of galaxies with nuclei that produce spectral line emission from highly ionized gas.
Present near-to-mid IR SEDs for 21 Seyfert galaxies using subarcsecond resolution imaging data. Aim: compare properties of Sy1 and Sy2 tori using clumpy torus models and a Bayesian approach to fit the IR nuclear SEDs. These dusty tori have physical sizes smaller than 6pc radius. Find evidence that strong unification may not hold; immediate dusty surroundings of Sy1 and Sy2 nuclei are intrinsically different. Type 2 tori studied are broader, have more clumps, and these clumps have lower optical depths than those of Type 1 tori. Larger the covering factor of the torus, the smaller the probability of having direct view of the AGN, and vice-versa. In the sample, Sy2 tori have larger covering factors (C_T=0.95 pm 0.02) and smaller escape probabilities than those of Sy1. On the basis of results presented here, the classification of a Seyfert galaxy may depend more on the intrinsic properties of the torus rather than on its mere inclination, in contradiction with the simplest unification model.
1201.4266
Radio-optical outlier quasars - a case study with ICRF2 and SDSS
Orosz, Frey
Find that DR7 astrometry is better than DR8, when compared to radio sources. The optical-to-radio offset may be due to dual AGN, etc.
1201.3920
AGN clustering in the X-ray band
Cappelluti, Allevato, Finoguenov
Review from 1988 to 2011 on X-ray clustering: First: clustering of CXB sources resembles that of optical QSO, then X-ray AGN are hosted by DM haloes of mass similar to that of galaxy groups; hypothesis of galaxy mergers constitute the main AGN triggering mechanism. However detailed analysis of observational data, acquired with modern telescopes along with the HOD models revealed that the triggering of an AGN could also be attributed to phenomena like tidal disruption or disk instability, and to galaxy evolution.
1201.3936
Globular cluster luminosity function as distance indicator
Rejkuba
Globular clusters: Differential magnitude distribution of old globular clusters is very similar in different galaxies presenting a peak at M_V~-7.5. This peak magnitude of the globular cluster luminosity function has been established as a secondary distance indicator. Intrinsic accuracy: ~0.2 mag. Recent results: show distance indicator depends on complex physics of the cluster formation and dynamical evolution, and can have dependencies on Hubble type [?], environment and dynamical history of the host galaxy. Corrections are often relatively small.
1201.3942
Dark Matter: a brief review
Peter
Review the current status of the search for the nature of dark matter. Provide an introduction to possible particle candidates for DM and highlight recent experimental astroparticle- and particle-physics results that constrain the properties of those candidates. Given the absence of detections in those experiments, advocate a return of the problem of DM identification to astronomy, and show what kinds of theoretical and observational work might be used to pin down the nature of DM once and for all. Intended for a broad astronomy audience.
1201.3989
The HST cluster SNe survey: III. correlated properties of types Ia SNe and their hosts at 0.9<z<1.46
Meyers, Aldering, Barbary, ... Dawson, ... Faccioli, Fakhouri, ... Gladders, Goldhaber, .. et al
Search for correlations between the properties of SNe and their host galaxies at high z. Use galaxy color and quantitative morphology to determine the red sequence in 25 clusters and develop a model to distinguish passively evolving early-type galaxies from SF galaxies in both clusters and the field. Identify 6 SN Ia hosts that are early-type cluster members and 11 SN Ia hosts that are early-type field galaxies. Confirm for the first time at z>0.9 that SNe Ia hosted by early-type galaxies brighten and fade more quickly than SN Ia hosted by late-type galaxies. Also show that the two samples of hosts produce SNe Ia with similar color distributions. Thow samples of hosts produce SNe Ia with similar color distributions. The relatively simple SEDs expected for passive galaxies enable measurement of stellar masses of early-type SN hosts. Combine with SM estimates of late-type GOODS SN hosts, investigate the correlation of host mass with Hubble residual observed at lower redshifts (sample small and uncertainties large). A hint of this relation found at z>0.9. Simultaneously fit the average cluster galaxy formation history and dust content to the red-sequence scatters: show that the reddening of early-type cluster SN hosts is likely E(B-V)<0.06. Similarity of the field and cluster early-type host samples suggests that field early-type galaxies that lie on the red sequence may also be minimally affected by dust. The early-type hosted SNeIa studied occupy a more favorable environment to use as well-characterized high-z standard candles than other SNIa.
1201.4011
Solar diameter with 2012 Venus transit
Sigismondi
Measure the diameter of the Sun better than 0.01 arcsec. Infer luminosity from size; compare with past values.
No comments:
Post a Comment