Wednesday.
NYT article: http://www.nytimes.com/2013/08/13/science/how-to-share-scientific-data.html
Who will pay for public access to research data?Berman
The US office of science and technology policy (OSTP) released a memo calling for public access for publications and data resulting from federally sponsored research grants. The memo directed federal agencies with more than $100 M R&D expenditures to "develop a plan to support increased public access to the results of research funded by the Federal Government." A subsequent NYT page sported the headline "We paid for the research, so let's see it." So who pays for data infrastructure?
1308.2227
A search for RR Lyrae stars in Segue 2 and Segue 3
Boettcher, Willman, Fadely, ... et al
Search for RR Lyrae stars in ultra-faint MW companions Segue 2 and 3. In Segue 2, Find a RRab star ["fundamental mode" RR Lyrae] with period P_ab=0.748 days. Revisit inverse correlation between <P_ab> and <[Fe/H]> established in the literature for MW dwarf galaxies and their RR Lyrae. The long period of Segue 2's RRab star, as well as the known significant spread in metallicity in this dwarf galaxy are consistent with the observed trend in <P_ab> and <[Fe/H]>. Derive the first robust distance to Segue 2, using both its RRab star and spectroscopically confirmed blue horizontal branch stars. Using [Fe/H]=-2.16 and -2.44 dex, find d_RRL=36.6 and 37.7 (pm 2.5-ish) kpc; assuming [Fe/H]=-2.257 dex, find d_BHB=34.4pm2.6kpc. Although no RRLyrae were present in the Segue 3 field, find a candidate eclipsing binary star system.
1308.2252
KeSeF - Kepler Self Follow-up Mission
Ofir
The Kepler spacecraft is currently unable to hold steady pointing and it is slowly drifting during observations. If one has to deal with targets that drift across the CCDs, one should at least be able to track to targets well enough to correct for some -- if not most -- of the problems caused by this drift. Propose to observe as many stars as possible in short cadence. Propose that at least all currently known planetary candidate host stars will be so observed, with possibly known Kepler eclipsing binaries, astroseismology targets, guest observer targets and new targets in increasingly lower priority. Also outline the modifications needed to flight SW in order to allow for such observations to take place, aiming to provide ample non-photometric data that should allow post-processing to recover most of the pre-failure photometric performance. In total, the KeSeF Mission will allow Kepler to follow up it's own previous discoveries in a way that is not otherwise possible. By doing so it will enable to continue persuing nearly all the science goals that made the original mission choose staring at a single field of view in the first place. [confusing last sentence. I guess the drift doesn't allow Kepler to stare at one point anymore.]
1308.2367
The 9 and 18 micron luminosity function of various types of galaxies with AKARI: implication for the dust torus structure of AGN
Toba et al
Present the 9 and 18 micron LFs of galaxies at 0.006<z<0.8 (avg z ~0.04) using AKARI MIR all-sky survey catalog. 243 galaxies at 9 um and 255 galaxies at 18 um from SDSS spectroscopy region; classified by their optical emission lines, such as Ha or [OIII]/Hbeta and [NII]/H_alpha into 5 types: Type 1 AGN, Type 2, low-ionization narrow emission lines (LINER); galaxies with both SF and narrow-line AGN activity (composite galaxies); and star forming galaxies (SF). Find that (i) the number density ratio of Type 2 to Type 1 AGNs is 1.73, which is larger than a result obtained from the optical LF and (ii) this ratio decreases with increasing 18 um luminosity.
1308.2398
Photometric identification of objects from Galaxy Evolution Explorer survey and Sloan digital sky survey
Preethi, et al
Used GALEX and SESS to get 7-band photometric mag of 80k objects near the North Galactic Pole. Although these have been identified as stars by the SDSS pipeline, found through fitting with model SEDs that most were in fact of extragalactic origin. [really? how was the original 80k "stellar" object chosen?] Only about 9% of these objects turned out to be MS stars, and about 11% were WDs and RGs collectively, while galaxies and quasars contributed to the remaining 80% of the data. Classified these objects into different spectral types (for the stars) and into different galactic types (for the galaxies). As part of the fitting procedure, derive the distance and extinction to each object and the photometric redshift towards galaxies and quasars. This method easily allows for the addition of any number of observations to cover a more diverse range of wavelengths, as well as the addition of any number of model templates. The primary objective of this work is to eventually derive a 3d extinction map of the MW galaxy [cool!].
1308.2533
Detecting filamentary pattern in the cosmic web: a catalogue of filaments for the SDSS
Tempel et al
The main feature of the spatial large-scale galaxy distribution is its intricate network of galaxy filaments. This network is spanned by the galaxy locations that can be interpreted as 3d point distribution. The global properties of the point process can be measured by different statistical methods, which, however, do not describe directly the structure elements. The morphology of the large scale structure is an important property of galaxy distribution. Apply an object point process with interactions (the Bisous model) to trace and extract the filamentary network in the presently largest galaxy redshift survey, SDSS. Search for filaments in the galaxy dsitribution having a radius of about 0.5 Mpc/h. Divide the detected network into single filaments and present a public catalogue of filaments. Study the filament length distribution and show that the longest filaments reach the length of 60 Mpc/h. The filaments contain 35-40% of the total galaxy luminosity and they cover roughly 5-8% of the total volume, in good agreement with N-body simulations and previous observational results.
1308.2534
Dark Matter
Einasto
Review of the development of the concept of DM. The DM story passed through several stages from a minor observational puzzle to a major challenge for theory of elementary particles. Modern data suggest that DM is the dominant matter component in the Universe, and that it consists of some unknown non-baryonic particles. DM is the dominant matter component in the Universe, thus properties of Dm particles determine the structure of the cosmic web.
1308.2551
Predictions for BAO distance estimates from the cross-correlaton of the Lyman-alpha forest and redshifted 21-cm emission
Sarkar, Bharadwaj
Investigate the possibility of using cross-correlation of Ly-a forest and redshifted 21-cm emission to detect the BAO. The standard Fisher matrix formalism used to determine the accuracy with which it will be possible to measure cosmological distances using this signal. Earlier predictions indicate that it will be possible to measure the dilation factor D_V with 1.9% accuracy at z=2.5 from the BOSS Ly-a forest auto-correlation. Investigate if it is possible to improve the accuracy using the cross-correlation. Use a simple parameterization of the Ly-a forest survey which very loosely matches some properties of BOSS and predicts delta D_V/D_V=2.0% for the auto-correlation at z=2.5. For the redshifted 21-cm observations, consider individual antennas of 2m*2m distributed such that the baselines within 250m are uniformly sampled. Assumed that the observations span z=2 to 3 and coveres the 10k deg^2 sky coverage of BOSS. Find that for 2 years of observation with an array of 2k antennas, the cross-corelation is 1.7 times more sensitive that the Ly-a forest auto-correlation. The cross-correlation is 2.7 times more sensitive than the auto-correlation if we have 4k antennas and 4 years of observation. In conclusion, find that it is possible to significantly increase the accuracy of the distance estimates by considering the cross-correlation signal. [question: how significant is the 21cm signal from z=2-3?]
1308.2816
Galaxy spin alignment in filaments and sheets: observational evidence
Tempel, Libeskind
Galaxy properties are known to be affected by their environment. One important question is how their angular momentum reflects the surrounding cosmic web. Use the SDS to investigate the spin axes of spiral and elliptical galaxies relative to their surrounding filament/sheet orientations. To detect filaments a marked point process with interactions (the "Bisous model") is used. Sheets are found by detecting "flattened" filaments. The minor axis of ellipticals are found to be preferential perpendicular to hosting filaments. A weak correlation is found with sheets [what do you mean? correlation of sheets and what?]. These findings are consistent with the notion that elliptical galaxies formed via mergers which predominantly occurred along the filaments. The spin axis of spiral galaxies is found to align with the host filament [really?? that would be cool, but I thought previous studies didn't find any correlation. Does this result contradict them?], with no correlation between spiral spin and sheet normal. When examined as a function of distance from the filament axis, a much stronger correlation is found in outer parts, suggesting that the alignment is driven by the laminar infall of gas from sheets to filaments [that would be so cool]. When compared with numerical simulations, results suggest that the connection between DM halo and galaxy spin is not straightforward. Results provide an important input to the understanding of how galaxies acquire their angular momentum.
1308.2669
The AGORA high-resolution galaxy simulations comparison project
Kim, Abel, ... Conroy, Dekel, Gnedin, Hahn, Hopkins, Klypin, Kravtsov, Krumholz, et al
AGORA project: a comprehensive numerical study of well-resolved galaxies within the LCDM cosmology. Cosmological hydrodynamic sims with force resolutions of ~100 proper pc or better will be run with a variety of code platforms to follow the hierarchical growth, SFH, morphological transformation, and the cycle of baryons in and out of 8 galaxies with halo masses M_vir ~ 1e10, 11, 12, and 13 Msun at z=0 and two different ("violent" and "quiescent") assembly histories. The numerical techniques and implementations used in this project include the smoothed particle hydrodynamics codes GADGET and GASOLINE, and the adaptive mesh refinement codes ART, ENZO, and RAMSES. The codes will share common initial conditions and common astrophysics packages including UV background, metal-dependent radiative cooling, metal and energy yields of supernovae, and stellar IMF. These are described in detail in the paper. Subgrid SF and feedback prescriptions will be tuned to provide a realistic interstellar and circumgalactic medium using a non-cosmological disk galaxy simulation. Cosmological runs will be systematically compared with each other using a common analysis toolkit [like what? PS?], and validated against observations to verify that the solutions are robust -- i.e., that the astrophysical assumptions are responsible for any success, rather than artifacts of particular implementations. The goals of the AGORA project are, broadly speaking, to raise the realism and the predictive power of galaxy simulations and the understanding of the feedback processes that regulate galaxy "metabolism." The proof-of-concept DM-only test of the formation of a galactic halo with a z=0 mass of M_vir ~ 1.7e11 Msun by 9 different versions of the participating codes is also presented to validate the infrastructure of the project.
NYT article: http://www.nytimes.com/2013/08/13/science/how-to-share-scientific-data.html
Who will pay for public access to research data?Berman
The US office of science and technology policy (OSTP) released a memo calling for public access for publications and data resulting from federally sponsored research grants. The memo directed federal agencies with more than $100 M R&D expenditures to "develop a plan to support increased public access to the results of research funded by the Federal Government." A subsequent NYT page sported the headline "We paid for the research, so let's see it." So who pays for data infrastructure?
1308.2227
A search for RR Lyrae stars in Segue 2 and Segue 3
Boettcher, Willman, Fadely, ... et al
Search for RR Lyrae stars in ultra-faint MW companions Segue 2 and 3. In Segue 2, Find a RRab star ["fundamental mode" RR Lyrae] with period P_ab=0.748 days. Revisit inverse correlation between <P_ab> and <[Fe/H]> established in the literature for MW dwarf galaxies and their RR Lyrae. The long period of Segue 2's RRab star, as well as the known significant spread in metallicity in this dwarf galaxy are consistent with the observed trend in <P_ab> and <[Fe/H]>. Derive the first robust distance to Segue 2, using both its RRab star and spectroscopically confirmed blue horizontal branch stars. Using [Fe/H]=-2.16 and -2.44 dex, find d_RRL=36.6 and 37.7 (pm 2.5-ish) kpc; assuming [Fe/H]=-2.257 dex, find d_BHB=34.4pm2.6kpc. Although no RRLyrae were present in the Segue 3 field, find a candidate eclipsing binary star system.
1308.2252
KeSeF - Kepler Self Follow-up Mission
Ofir
The Kepler spacecraft is currently unable to hold steady pointing and it is slowly drifting during observations. If one has to deal with targets that drift across the CCDs, one should at least be able to track to targets well enough to correct for some -- if not most -- of the problems caused by this drift. Propose to observe as many stars as possible in short cadence. Propose that at least all currently known planetary candidate host stars will be so observed, with possibly known Kepler eclipsing binaries, astroseismology targets, guest observer targets and new targets in increasingly lower priority. Also outline the modifications needed to flight SW in order to allow for such observations to take place, aiming to provide ample non-photometric data that should allow post-processing to recover most of the pre-failure photometric performance. In total, the KeSeF Mission will allow Kepler to follow up it's own previous discoveries in a way that is not otherwise possible. By doing so it will enable to continue persuing nearly all the science goals that made the original mission choose staring at a single field of view in the first place. [confusing last sentence. I guess the drift doesn't allow Kepler to stare at one point anymore.]
1308.2367
The 9 and 18 micron luminosity function of various types of galaxies with AKARI: implication for the dust torus structure of AGN
Toba et al
Present the 9 and 18 micron LFs of galaxies at 0.006<z<0.8 (avg z ~0.04) using AKARI MIR all-sky survey catalog. 243 galaxies at 9 um and 255 galaxies at 18 um from SDSS spectroscopy region; classified by their optical emission lines, such as Ha or [OIII]/Hbeta and [NII]/H_alpha into 5 types: Type 1 AGN, Type 2, low-ionization narrow emission lines (LINER); galaxies with both SF and narrow-line AGN activity (composite galaxies); and star forming galaxies (SF). Find that (i) the number density ratio of Type 2 to Type 1 AGNs is 1.73, which is larger than a result obtained from the optical LF and (ii) this ratio decreases with increasing 18 um luminosity.
1308.2398
Photometric identification of objects from Galaxy Evolution Explorer survey and Sloan digital sky survey
Preethi, et al
Used GALEX and SESS to get 7-band photometric mag of 80k objects near the North Galactic Pole. Although these have been identified as stars by the SDSS pipeline, found through fitting with model SEDs that most were in fact of extragalactic origin. [really? how was the original 80k "stellar" object chosen?] Only about 9% of these objects turned out to be MS stars, and about 11% were WDs and RGs collectively, while galaxies and quasars contributed to the remaining 80% of the data. Classified these objects into different spectral types (for the stars) and into different galactic types (for the galaxies). As part of the fitting procedure, derive the distance and extinction to each object and the photometric redshift towards galaxies and quasars. This method easily allows for the addition of any number of observations to cover a more diverse range of wavelengths, as well as the addition of any number of model templates. The primary objective of this work is to eventually derive a 3d extinction map of the MW galaxy [cool!].
1308.2533
Detecting filamentary pattern in the cosmic web: a catalogue of filaments for the SDSS
Tempel et al
The main feature of the spatial large-scale galaxy distribution is its intricate network of galaxy filaments. This network is spanned by the galaxy locations that can be interpreted as 3d point distribution. The global properties of the point process can be measured by different statistical methods, which, however, do not describe directly the structure elements. The morphology of the large scale structure is an important property of galaxy distribution. Apply an object point process with interactions (the Bisous model) to trace and extract the filamentary network in the presently largest galaxy redshift survey, SDSS. Search for filaments in the galaxy dsitribution having a radius of about 0.5 Mpc/h. Divide the detected network into single filaments and present a public catalogue of filaments. Study the filament length distribution and show that the longest filaments reach the length of 60 Mpc/h. The filaments contain 35-40% of the total galaxy luminosity and they cover roughly 5-8% of the total volume, in good agreement with N-body simulations and previous observational results.
1308.2534
Dark Matter
Einasto
Review of the development of the concept of DM. The DM story passed through several stages from a minor observational puzzle to a major challenge for theory of elementary particles. Modern data suggest that DM is the dominant matter component in the Universe, and that it consists of some unknown non-baryonic particles. DM is the dominant matter component in the Universe, thus properties of Dm particles determine the structure of the cosmic web.
1308.2551
Predictions for BAO distance estimates from the cross-correlaton of the Lyman-alpha forest and redshifted 21-cm emission
Sarkar, Bharadwaj
Investigate the possibility of using cross-correlation of Ly-a forest and redshifted 21-cm emission to detect the BAO. The standard Fisher matrix formalism used to determine the accuracy with which it will be possible to measure cosmological distances using this signal. Earlier predictions indicate that it will be possible to measure the dilation factor D_V with 1.9% accuracy at z=2.5 from the BOSS Ly-a forest auto-correlation. Investigate if it is possible to improve the accuracy using the cross-correlation. Use a simple parameterization of the Ly-a forest survey which very loosely matches some properties of BOSS and predicts delta D_V/D_V=2.0% for the auto-correlation at z=2.5. For the redshifted 21-cm observations, consider individual antennas of 2m*2m distributed such that the baselines within 250m are uniformly sampled. Assumed that the observations span z=2 to 3 and coveres the 10k deg^2 sky coverage of BOSS. Find that for 2 years of observation with an array of 2k antennas, the cross-corelation is 1.7 times more sensitive that the Ly-a forest auto-correlation. The cross-correlation is 2.7 times more sensitive than the auto-correlation if we have 4k antennas and 4 years of observation. In conclusion, find that it is possible to significantly increase the accuracy of the distance estimates by considering the cross-correlation signal. [question: how significant is the 21cm signal from z=2-3?]
1308.2816
Galaxy spin alignment in filaments and sheets: observational evidence
Tempel, Libeskind
Galaxy properties are known to be affected by their environment. One important question is how their angular momentum reflects the surrounding cosmic web. Use the SDS to investigate the spin axes of spiral and elliptical galaxies relative to their surrounding filament/sheet orientations. To detect filaments a marked point process with interactions (the "Bisous model") is used. Sheets are found by detecting "flattened" filaments. The minor axis of ellipticals are found to be preferential perpendicular to hosting filaments. A weak correlation is found with sheets [what do you mean? correlation of sheets and what?]. These findings are consistent with the notion that elliptical galaxies formed via mergers which predominantly occurred along the filaments. The spin axis of spiral galaxies is found to align with the host filament [really?? that would be cool, but I thought previous studies didn't find any correlation. Does this result contradict them?], with no correlation between spiral spin and sheet normal. When examined as a function of distance from the filament axis, a much stronger correlation is found in outer parts, suggesting that the alignment is driven by the laminar infall of gas from sheets to filaments [that would be so cool]. When compared with numerical simulations, results suggest that the connection between DM halo and galaxy spin is not straightforward. Results provide an important input to the understanding of how galaxies acquire their angular momentum.
1308.2669
The AGORA high-resolution galaxy simulations comparison project
Kim, Abel, ... Conroy, Dekel, Gnedin, Hahn, Hopkins, Klypin, Kravtsov, Krumholz, et al
AGORA project: a comprehensive numerical study of well-resolved galaxies within the LCDM cosmology. Cosmological hydrodynamic sims with force resolutions of ~100 proper pc or better will be run with a variety of code platforms to follow the hierarchical growth, SFH, morphological transformation, and the cycle of baryons in and out of 8 galaxies with halo masses M_vir ~ 1e10, 11, 12, and 13 Msun at z=0 and two different ("violent" and "quiescent") assembly histories. The numerical techniques and implementations used in this project include the smoothed particle hydrodynamics codes GADGET and GASOLINE, and the adaptive mesh refinement codes ART, ENZO, and RAMSES. The codes will share common initial conditions and common astrophysics packages including UV background, metal-dependent radiative cooling, metal and energy yields of supernovae, and stellar IMF. These are described in detail in the paper. Subgrid SF and feedback prescriptions will be tuned to provide a realistic interstellar and circumgalactic medium using a non-cosmological disk galaxy simulation. Cosmological runs will be systematically compared with each other using a common analysis toolkit [like what? PS?], and validated against observations to verify that the solutions are robust -- i.e., that the astrophysical assumptions are responsible for any success, rather than artifacts of particular implementations. The goals of the AGORA project are, broadly speaking, to raise the realism and the predictive power of galaxy simulations and the understanding of the feedback processes that regulate galaxy "metabolism." The proof-of-concept DM-only test of the formation of a galactic halo with a z=0 mass of M_vir ~ 1.7e11 Msun by 9 different versions of the participating codes is also presented to validate the infrastructure of the project.
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