Thursday.
1306.5746
Luminosity of young Jupiters revisited. massive cores make host planets
Mordasini
Intrinsic luminosity of young Jupiters is of high interest for planet formation theory. Related to physical mechanisms during formation are the accretion shock structure and the basic formation mechanism (core accretion of gravitational instability). Study the impact of the core mass on the post-formation entropy and luminosity of young giant planets forming via core accretion with a super critical shock (cold accretion). Conduct self-consistently coupled formation and evolution calculations of giant planets with masses between 1 and 12 Jovian masses and core masses between 20 and 120 Earth masses. Find that the post-formation luminosity of massive giant planets is very sensitive to core mass. An increase of the core mass by a factor 6 results in an increase of post-formation luminosity of a 10 Jovian mass planet by a factor 120. Due to this dependency, there is no single well defined post-formation luminosity for core accretion, but a wide range. For massive cores (~100 Earth masses), the post-formation luminosities of core accretion planets become so high that they approach those in the host start scenario that is often associated with gravitational instability. For the mechanism to work, it is necessary that the solids are accreted before or during gas runaway accretion, and that they sink deep into the planet. Make no claims whether or not such massive cores can actually form in giant planets. BUt if yes, it becomes difficult to rule out core accretion as formation mechanism based solely on luminosity for directly imaged planets that are more luminous than predicted for low core masses. Instead of invoking gravitational instability as the consequently necessary formation mode, the high luminosity could also be caused simply by a more massive core.
1306.5751
Teasing bits of information out of the CMB energy spectrum
Chuluba, Jeong
CMB spectral distortions (departures from BB) encode information about the thermal history of the early Universe (1e3<z<few 1e6). While the signal is usually characterized as mu- and y-type distortion, a smaller residual (non-y/non-mu) distortion can also be created at intermediate redshifts 1e4<z<3e5. Here, construct a new set of observables, nu_i, that describes the principal components of this residual distortion. The principal components are orthogonal to temperature shift, y- and mu-type distortion, and ranked by their detectability, thereby delivering a compression of all valuable information offered by the CMB spectrum. This method provides an efficient way of analyzing the spectral distortion for given experimental settings, and can be applied to a wide range of energy-release scenarios. As an illustration, discuss the analysis of the spectral distortion signatures caused by dissipation of small-scale acoustic waves and decaying/annihilating particles for a PIXIE-type experiments. Provide forecasts for the expected measurement uncertainties of model-parameters and detections limits in each case. Furthermore show that a PIXIE-type experiments can in principle distinguish dissipative energy release from particle decays for a nearby scale-invariant primordial PS with small running. Future CMB spectroscopy thus offers a unique way to probe physics in the primordial Universe. [what's the PIXIE experiment?]
1306.5752
Galaxy and mass assembly (GAMA): witnessing the assembly of the cluster Abell 1882
Owers et al
Combined optical and X-ray analysis of the rich cluster Abell 1882 with the aim of identifying merging substructure and understanding the recent assembly history of this system. Optical from GAMA; use 283 spectroscopically confirmed cluster members to detect and characterize substructure. X-ray from Chandra and XMM. A1882 harbors two main components A and B, which have a projected separation of 2 Mpc and a LoS velocity difference of -428 km/s. The primary system A has velocity dispersion sigma_v=500km/s and Chandra (XMM) temperature kT=3.57keV (3.31keV); B has sigma_v=457km/s and kT=2.39keV (2.12keV). The optical and X-ray estimates for the masses of the two systems are consistent within the uncertainties and indicate that there is twice as much mass in A (M_500=1.5-1.9e14 Msun) than B (0.8-1.0e14 Msun). Interpret the A+B system as being observed prior to a core passage. Supporting this interpretation is the large projected separation of A+B and the dearth of evidence for a recent (<2 Gyr) major interaction in the X-ray data. Two-body analyses indicate that A and B form a bound system with bound incoming solutions strongly favored. Compute blue fractions of f_b=0.28 and 0.18 for the spectroscopically confirmed member galaxies within r_500 of the centers of A and B, respectively. These blue fractions do not differ significantly from the blue fraction measured from an ensemble of 20 clusters with similar redshift.
1306.5771
Panphasia: a user guide
Jenkins, Booth
Make a very large realization of a Gaussian white noise field, called PANPHASIA, public by releasing SW that computes this field. Panphasia is designed specifically for setting up Gaussian IC for cosmo sims and re-simulations of structure formation. Illustrate applications, including a modified version of a public serial IC generator. Document the SW and present the results of a few basic tests of the field. The properties and method of construction of Panphasia are described in full in a companion paper Jenkins 2013.
1306.5798
Clues on void evolution I: large scale galaxy distributions around voids
Ceccarelli, Paz, Lares, Padilla, Lambas
Statistical void environment study: examine galaxy density profiles around voids in the SDSS, finding a correlation between void-centric distance to the shell of maximum density and void radius when a maximum in overdensity exists. Analyze voids with and without a surrounding over-dense shell in the SDSS. Find that small voids are more frequently surrounded by over-dense shells whereas the radial galaxy density profile of large voids tends to rise smoothly towards the mean galaxy density. Analyze the fraction of voids surrounded by overdense shells finding a continuous trend with void radius. The differences between voids with and without an overdense shell around them can be understood in terms of whether the voids are, on average, in the process of collapsing [collapse?] or continuing their expansion, respectively, in agreement with previous theoretical expectations. Use numerical simulations coupled to SAM of galaxy formation in order to test and interpret results. The very good agreement between the mock catalog results and the observations provides additional support to the viability of a LCDM model to reproduce the LSS of the universe as defined by the void network, in a way which has not been analysed previously.
1306.5896
The one-dimensional Ly-alpha forest power spectrum from BOSS
Palanque-Delabrouille et al
Develop 2 independent methods to measure the one-dimensional PS of the transmitted flux in the Ly-a forest. The first method is based on a Fourier transform, and the second on a maximum likelihood estimator. The two methods are independent and have different systematic uncertainties. The determination of the noise level in the data spectra was subject to a novel treatment, because of its significant impact on the derived power spectrum. Apply the two methods to 13821 quasar spectra from DR9, selected from a larger sample of >60k spectra on the basis of their quality, S/N, and spectral resolution. The PS measured using either approach are in good agreement over all twelve redshift bins from <z>=2.2 to 4.4, and scales from 0.001(km/s)^-1 to 0.02(km/s)^-1. Determine the methodological and instrumental systematic uncertainties of our measurements. Provide a preliminary cosmological interpretation of measurements using available hydrodynamical simulations. The improvement in precision over previous results is a factor 2-3 for constraints on relevant cosmological parameters. For a LCDM model and using a constraint on H0 that encompasses measurements based on the local distance ladder and on CMB anisotropies, infer sigma_8=0.83pm0.03 and n_s=0.97pm0.02 based on HI absorption in the range 2.1<z<3.7.
1306.5968
A new way of setting the phases for cosmological multi-scale gaussian initial conditions
Jenkins
Describe how to define an extremely large discrete realization of a Gaussian white noise field that has a hierarchical structure and the property that the value of any part of the field can be computed quickly. Tiny subregions of such a field can be used to set the phase information for Gaussian IC for individual cosmological simulations of structure formation. This approach has several attractive features: (i) the hierarchical structure based on an octree is particular well suited for generating follow up resimulation or zoom initial conditions; (ii) the phases are defined for all relevant physical scales in advance so that resimulation ICs are, by construction, consistent both with their parent simulation and with each other; (iii) the field can easily be made public by releasing a code to compute it - once public, phase information can be shared or published by specifying a spatial location within the realization. In this paper describe the principles behind creating such realizations. Define an example called PANPHASIA and in a companion paper on arXiv, make public a code to compute it. With 50 octree levels Panphasia spans a factor of more than 1e15 in linear scale - a range that significantly exceeds the ratio of the current Hubble radius to the putative CDM free-streaming scale. Show how to modify a code used for making cosmo and resimulation ICs so that it can take the phase information from Panphasia and, using this code, demonstrate that it is possible to make good quality resimulation ICs. Define a convention for publishing phase information from Panphasia and publish the initial phases for several of the Virgo Consortium's most recent cosmological simulations including the 303 billion particle MXXL simulation.
1306.6096
The mass-concentration relation in massive galaxy clusters at redshift ~1
Sereno, Covone
Mass and concentration of clusters of galaxies are related and evolving with redshift. Study the properties of a sample of 31 massive galaxy clusters at high z, 0.8<z<1.5, using WL and SL observations. Concentration is a steep function of mass, c_200~M_200^(-0.83pm0.39), with higher-redshift clusters being less concentrated. Mass and concentration from the stacked analysis, M_200=4.1e14 Msun/h and c_200=2.3pm0.2 are in line with theoretical results extrapolated from the local universe. Clusters with signs of dynamical activity preferentially feature high concentrations. Discuss the possibility that the whole sample is a mix of two different kinds of haloes. Over-concentrated clusters might be accreting haloes out of equilibrium in a transient phase of compression, whereas less concentrated ones might be more relaxed.
1306.6117
Galaxy clusters in the line of sight to background quasars - III multi-object spectroscopy
Andrews, ... Gladders, Yee, et al
Present multi-object spectroscopy of 31 galaxy cluster candidates at 0.2<z<1.0 and centered on QSO sight-lines taken from Lopez+(2008). The targets were selected based on the presence of an intervening MgII absorption system at a similar redshift to that of a galaxy cluster candidate lying at a projected distance < 2Mpc/h from the QSO sight-line (a 'photometric-hit'). The absorption systems span rest-frame equivalent widths between 0.015 and 2.028 A. Aim: (1) identify the absorbing galaxies and determine their impact parameters, (2) confirm the galaxy cluster candidates in the vicinity of each quasar sightline, (3) determine whether the absorbing galaxies reside in galaxy clusters. Findings: (1) 10/24 absorbing galaxies identified, with z up to 1.0955. (2) 20/31 cluster/group candidates spectroscopically confirmed, with most of the confirmed clusters/groups at z<0.7. (3) 10/14 spectro confirmation of photometric hits within ~650 km/s from galaxy clusters/groups, in addition to 2 new ones related to galaxy group environments. These number imply efficiencies of 71% in finding such systems with MOS spectroscopy. This is remarkable, since a photometric hit was defined as those cluster-absorber pairs having a redshift difference dz=0.1. Absorbing cluster-galaxies hosting weak absorbers are consistent with lower SF activity than the rest, which produce strong absorption and agree with typical MgII absorbing galaxies found in the literature. Spectroscopic confirmations lend support to the selection of photometric hits made in Lopez+(2008).
1306.6148
Is GBT 1355+5439 a dark galaxy?
Oosterloo, Heald, de Blok
Present HI imaging of GBT 1355+5439 with Westerbork Synthesis Radio Telescope. This is a dark HI object recently discovered close to the nearby galaxy M101. Find this object to be an HI cloud 5x3 arcmin in size. THe total HI image in and the kinematics show that the cloud consists of condensations that have small (~10 km/s) motions with respect to each other. THe column densities of the HI are low; the observed peak value is 7.1e19 cm^-2. The velocity field shows a mild velocity gradient over the body of this object, possibly due to rotation, but it may also indicate large-scale radial motions. Data limited in sensitivity, but at all positions the HI velocity dispersion is higher than 5 km/s and no narrow, cold, HI component is seen. Because its distance is not known, consider various possibilities for the nature of this object. Both scenarios of a tidal remnant near M101 and that it is a dark dwarf companion of M101 meet difficulties. Neither do the data fit the properties of known compact high-velocity clouds in the galactic halo exactly, but we cannot entirely exclude this option and deeper observations are required. Also considered the possibility that this object is a gas-rich dark minihalo in the outer regions of the Local Group. It would then have similar properties as the clouds of a proposed Local Group population recently found in the ALFALFA survey. In this case, the HI mass of this object would be about a few times 1e5 Msun, its size about 1kpc, and the dynamical mass M_dyn > 5e7 Msun. However, if this is a dark Local Group object, the internal kinematics of the HI appears to be different from that of gas-dominated, almost dark galaxies of similar size.
1306.6151
Source-lens clustering bias of weak-lensing estimators
Valageas
Estimate the amplitude of the source-lens clustering bias of weak lensing estimators of the 2-pt and 3-pt convergence and cosmic shear correlation functions. Use a linear galaxy bias model for the galaxy-density correlations. For the 3-pt and 4-pt density correlations, use analytical or semi-analytical models, based on a hierarchical ansatz or a combination of one-loop perturbation theory with a halo model. For two-point statistics, find that the source-lens clustering bias is typically several orders of magnitude below the weak lensing signal, except when we correlate a low-redshift galaxy (z<0.05) with a higher redshift galaxy (z>0.5), where it can reach 10% of the signal for the shear. For 3-pt statistics, the source-lens clustering bias is typically of order 10% of the signal, as soon as the 3 galaxy source redshifts are not identical.
1306.6191
Low-resolution spectrum of the Zodiacal light with AKARI InfraRed camera
Tsumura et al
Present NIR and MIR zodiacal light spectrum from AKARI IRC. A catalog of 278 spectra of the diffuse sky covering a wide range of Galactic and ecliptic latitudes constructed. Wavelength range: 1.8-5.3 um with resolution of lambda/Delta lambda ~ 20. Analysis of the spectra collected in different seasons and ecliptic latitudes, confirm that the spectral shape of the scattered component and the thermal emission component of zodiacal light does not show any dependence on location and time, but relative brightness between them varies with location. Also confirmed that the color temperature of the zodiacal emission at 3-5 um is 300 pm 10 K at any ecliptic latitude. This emission is expected to be originated from sub-micron dust particles in interplanetary space.
1306.5746
Luminosity of young Jupiters revisited. massive cores make host planets
Mordasini
Intrinsic luminosity of young Jupiters is of high interest for planet formation theory. Related to physical mechanisms during formation are the accretion shock structure and the basic formation mechanism (core accretion of gravitational instability). Study the impact of the core mass on the post-formation entropy and luminosity of young giant planets forming via core accretion with a super critical shock (cold accretion). Conduct self-consistently coupled formation and evolution calculations of giant planets with masses between 1 and 12 Jovian masses and core masses between 20 and 120 Earth masses. Find that the post-formation luminosity of massive giant planets is very sensitive to core mass. An increase of the core mass by a factor 6 results in an increase of post-formation luminosity of a 10 Jovian mass planet by a factor 120. Due to this dependency, there is no single well defined post-formation luminosity for core accretion, but a wide range. For massive cores (~100 Earth masses), the post-formation luminosities of core accretion planets become so high that they approach those in the host start scenario that is often associated with gravitational instability. For the mechanism to work, it is necessary that the solids are accreted before or during gas runaway accretion, and that they sink deep into the planet. Make no claims whether or not such massive cores can actually form in giant planets. BUt if yes, it becomes difficult to rule out core accretion as formation mechanism based solely on luminosity for directly imaged planets that are more luminous than predicted for low core masses. Instead of invoking gravitational instability as the consequently necessary formation mode, the high luminosity could also be caused simply by a more massive core.
1306.5751
Teasing bits of information out of the CMB energy spectrum
Chuluba, Jeong
CMB spectral distortions (departures from BB) encode information about the thermal history of the early Universe (1e3<z<few 1e6). While the signal is usually characterized as mu- and y-type distortion, a smaller residual (non-y/non-mu) distortion can also be created at intermediate redshifts 1e4<z<3e5. Here, construct a new set of observables, nu_i, that describes the principal components of this residual distortion. The principal components are orthogonal to temperature shift, y- and mu-type distortion, and ranked by their detectability, thereby delivering a compression of all valuable information offered by the CMB spectrum. This method provides an efficient way of analyzing the spectral distortion for given experimental settings, and can be applied to a wide range of energy-release scenarios. As an illustration, discuss the analysis of the spectral distortion signatures caused by dissipation of small-scale acoustic waves and decaying/annihilating particles for a PIXIE-type experiments. Provide forecasts for the expected measurement uncertainties of model-parameters and detections limits in each case. Furthermore show that a PIXIE-type experiments can in principle distinguish dissipative energy release from particle decays for a nearby scale-invariant primordial PS with small running. Future CMB spectroscopy thus offers a unique way to probe physics in the primordial Universe. [what's the PIXIE experiment?]
1306.5752
Galaxy and mass assembly (GAMA): witnessing the assembly of the cluster Abell 1882
Owers et al
Combined optical and X-ray analysis of the rich cluster Abell 1882 with the aim of identifying merging substructure and understanding the recent assembly history of this system. Optical from GAMA; use 283 spectroscopically confirmed cluster members to detect and characterize substructure. X-ray from Chandra and XMM. A1882 harbors two main components A and B, which have a projected separation of 2 Mpc and a LoS velocity difference of -428 km/s. The primary system A has velocity dispersion sigma_v=500km/s and Chandra (XMM) temperature kT=3.57keV (3.31keV); B has sigma_v=457km/s and kT=2.39keV (2.12keV). The optical and X-ray estimates for the masses of the two systems are consistent within the uncertainties and indicate that there is twice as much mass in A (M_500=1.5-1.9e14 Msun) than B (0.8-1.0e14 Msun). Interpret the A+B system as being observed prior to a core passage. Supporting this interpretation is the large projected separation of A+B and the dearth of evidence for a recent (<2 Gyr) major interaction in the X-ray data. Two-body analyses indicate that A and B form a bound system with bound incoming solutions strongly favored. Compute blue fractions of f_b=0.28 and 0.18 for the spectroscopically confirmed member galaxies within r_500 of the centers of A and B, respectively. These blue fractions do not differ significantly from the blue fraction measured from an ensemble of 20 clusters with similar redshift.
1306.5771
Panphasia: a user guide
Jenkins, Booth
Make a very large realization of a Gaussian white noise field, called PANPHASIA, public by releasing SW that computes this field. Panphasia is designed specifically for setting up Gaussian IC for cosmo sims and re-simulations of structure formation. Illustrate applications, including a modified version of a public serial IC generator. Document the SW and present the results of a few basic tests of the field. The properties and method of construction of Panphasia are described in full in a companion paper Jenkins 2013.
1306.5798
Clues on void evolution I: large scale galaxy distributions around voids
Ceccarelli, Paz, Lares, Padilla, Lambas
Statistical void environment study: examine galaxy density profiles around voids in the SDSS, finding a correlation between void-centric distance to the shell of maximum density and void radius when a maximum in overdensity exists. Analyze voids with and without a surrounding over-dense shell in the SDSS. Find that small voids are more frequently surrounded by over-dense shells whereas the radial galaxy density profile of large voids tends to rise smoothly towards the mean galaxy density. Analyze the fraction of voids surrounded by overdense shells finding a continuous trend with void radius. The differences between voids with and without an overdense shell around them can be understood in terms of whether the voids are, on average, in the process of collapsing [collapse?] or continuing their expansion, respectively, in agreement with previous theoretical expectations. Use numerical simulations coupled to SAM of galaxy formation in order to test and interpret results. The very good agreement between the mock catalog results and the observations provides additional support to the viability of a LCDM model to reproduce the LSS of the universe as defined by the void network, in a way which has not been analysed previously.
1306.5896
The one-dimensional Ly-alpha forest power spectrum from BOSS
Palanque-Delabrouille et al
Develop 2 independent methods to measure the one-dimensional PS of the transmitted flux in the Ly-a forest. The first method is based on a Fourier transform, and the second on a maximum likelihood estimator. The two methods are independent and have different systematic uncertainties. The determination of the noise level in the data spectra was subject to a novel treatment, because of its significant impact on the derived power spectrum. Apply the two methods to 13821 quasar spectra from DR9, selected from a larger sample of >60k spectra on the basis of their quality, S/N, and spectral resolution. The PS measured using either approach are in good agreement over all twelve redshift bins from <z>=2.2 to 4.4, and scales from 0.001(km/s)^-1 to 0.02(km/s)^-1. Determine the methodological and instrumental systematic uncertainties of our measurements. Provide a preliminary cosmological interpretation of measurements using available hydrodynamical simulations. The improvement in precision over previous results is a factor 2-3 for constraints on relevant cosmological parameters. For a LCDM model and using a constraint on H0 that encompasses measurements based on the local distance ladder and on CMB anisotropies, infer sigma_8=0.83pm0.03 and n_s=0.97pm0.02 based on HI absorption in the range 2.1<z<3.7.
1306.5968
A new way of setting the phases for cosmological multi-scale gaussian initial conditions
Jenkins
Describe how to define an extremely large discrete realization of a Gaussian white noise field that has a hierarchical structure and the property that the value of any part of the field can be computed quickly. Tiny subregions of such a field can be used to set the phase information for Gaussian IC for individual cosmological simulations of structure formation. This approach has several attractive features: (i) the hierarchical structure based on an octree is particular well suited for generating follow up resimulation or zoom initial conditions; (ii) the phases are defined for all relevant physical scales in advance so that resimulation ICs are, by construction, consistent both with their parent simulation and with each other; (iii) the field can easily be made public by releasing a code to compute it - once public, phase information can be shared or published by specifying a spatial location within the realization. In this paper describe the principles behind creating such realizations. Define an example called PANPHASIA and in a companion paper on arXiv, make public a code to compute it. With 50 octree levels Panphasia spans a factor of more than 1e15 in linear scale - a range that significantly exceeds the ratio of the current Hubble radius to the putative CDM free-streaming scale. Show how to modify a code used for making cosmo and resimulation ICs so that it can take the phase information from Panphasia and, using this code, demonstrate that it is possible to make good quality resimulation ICs. Define a convention for publishing phase information from Panphasia and publish the initial phases for several of the Virgo Consortium's most recent cosmological simulations including the 303 billion particle MXXL simulation.
1306.6096
The mass-concentration relation in massive galaxy clusters at redshift ~1
Sereno, Covone
Mass and concentration of clusters of galaxies are related and evolving with redshift. Study the properties of a sample of 31 massive galaxy clusters at high z, 0.8<z<1.5, using WL and SL observations. Concentration is a steep function of mass, c_200~M_200^(-0.83pm0.39), with higher-redshift clusters being less concentrated. Mass and concentration from the stacked analysis, M_200=4.1e14 Msun/h and c_200=2.3pm0.2 are in line with theoretical results extrapolated from the local universe. Clusters with signs of dynamical activity preferentially feature high concentrations. Discuss the possibility that the whole sample is a mix of two different kinds of haloes. Over-concentrated clusters might be accreting haloes out of equilibrium in a transient phase of compression, whereas less concentrated ones might be more relaxed.
1306.6117
Galaxy clusters in the line of sight to background quasars - III multi-object spectroscopy
Andrews, ... Gladders, Yee, et al
Present multi-object spectroscopy of 31 galaxy cluster candidates at 0.2<z<1.0 and centered on QSO sight-lines taken from Lopez+(2008). The targets were selected based on the presence of an intervening MgII absorption system at a similar redshift to that of a galaxy cluster candidate lying at a projected distance < 2Mpc/h from the QSO sight-line (a 'photometric-hit'). The absorption systems span rest-frame equivalent widths between 0.015 and 2.028 A. Aim: (1) identify the absorbing galaxies and determine their impact parameters, (2) confirm the galaxy cluster candidates in the vicinity of each quasar sightline, (3) determine whether the absorbing galaxies reside in galaxy clusters. Findings: (1) 10/24 absorbing galaxies identified, with z up to 1.0955. (2) 20/31 cluster/group candidates spectroscopically confirmed, with most of the confirmed clusters/groups at z<0.7. (3) 10/14 spectro confirmation of photometric hits within ~650 km/s from galaxy clusters/groups, in addition to 2 new ones related to galaxy group environments. These number imply efficiencies of 71% in finding such systems with MOS spectroscopy. This is remarkable, since a photometric hit was defined as those cluster-absorber pairs having a redshift difference dz=0.1. Absorbing cluster-galaxies hosting weak absorbers are consistent with lower SF activity than the rest, which produce strong absorption and agree with typical MgII absorbing galaxies found in the literature. Spectroscopic confirmations lend support to the selection of photometric hits made in Lopez+(2008).
1306.6148
Is GBT 1355+5439 a dark galaxy?
Oosterloo, Heald, de Blok
Present HI imaging of GBT 1355+5439 with Westerbork Synthesis Radio Telescope. This is a dark HI object recently discovered close to the nearby galaxy M101. Find this object to be an HI cloud 5x3 arcmin in size. THe total HI image in and the kinematics show that the cloud consists of condensations that have small (~10 km/s) motions with respect to each other. THe column densities of the HI are low; the observed peak value is 7.1e19 cm^-2. The velocity field shows a mild velocity gradient over the body of this object, possibly due to rotation, but it may also indicate large-scale radial motions. Data limited in sensitivity, but at all positions the HI velocity dispersion is higher than 5 km/s and no narrow, cold, HI component is seen. Because its distance is not known, consider various possibilities for the nature of this object. Both scenarios of a tidal remnant near M101 and that it is a dark dwarf companion of M101 meet difficulties. Neither do the data fit the properties of known compact high-velocity clouds in the galactic halo exactly, but we cannot entirely exclude this option and deeper observations are required. Also considered the possibility that this object is a gas-rich dark minihalo in the outer regions of the Local Group. It would then have similar properties as the clouds of a proposed Local Group population recently found in the ALFALFA survey. In this case, the HI mass of this object would be about a few times 1e5 Msun, its size about 1kpc, and the dynamical mass M_dyn > 5e7 Msun. However, if this is a dark Local Group object, the internal kinematics of the HI appears to be different from that of gas-dominated, almost dark galaxies of similar size.
1306.6151
Source-lens clustering bias of weak-lensing estimators
Valageas
Estimate the amplitude of the source-lens clustering bias of weak lensing estimators of the 2-pt and 3-pt convergence and cosmic shear correlation functions. Use a linear galaxy bias model for the galaxy-density correlations. For the 3-pt and 4-pt density correlations, use analytical or semi-analytical models, based on a hierarchical ansatz or a combination of one-loop perturbation theory with a halo model. For two-point statistics, find that the source-lens clustering bias is typically several orders of magnitude below the weak lensing signal, except when we correlate a low-redshift galaxy (z<0.05) with a higher redshift galaxy (z>0.5), where it can reach 10% of the signal for the shear. For 3-pt statistics, the source-lens clustering bias is typically of order 10% of the signal, as soon as the 3 galaxy source redshifts are not identical.
1306.6191
Low-resolution spectrum of the Zodiacal light with AKARI InfraRed camera
Tsumura et al
Present NIR and MIR zodiacal light spectrum from AKARI IRC. A catalog of 278 spectra of the diffuse sky covering a wide range of Galactic and ecliptic latitudes constructed. Wavelength range: 1.8-5.3 um with resolution of lambda/Delta lambda ~ 20. Analysis of the spectra collected in different seasons and ecliptic latitudes, confirm that the spectral shape of the scattered component and the thermal emission component of zodiacal light does not show any dependence on location and time, but relative brightness between them varies with location. Also confirmed that the color temperature of the zodiacal emission at 3-5 um is 300 pm 10 K at any ecliptic latitude. This emission is expected to be originated from sub-micron dust particles in interplanetary space.
No comments:
Post a Comment