1901.02009
High redshift massive quiescent galaxies are as flat as star forming galaxies: the flattening of galaxies and the correlation with structural properties in CANDELS/3D-HST
Hill, et al
Investigate the median flattening of galaxies at 0.2<z<4.0 in all five CANDELS/3D-HST fields via the apparent axis ratio q. Separate the sample into bins of z, stellar-mass, sersic index, size and UVJ determined SF state to discover the most important drivers of the median q (q_med). Quiescent galaxies at z<1 and M*>1e11 Msun are rounder than those at lower masses, consistent with the hypothesis that they have grown significantly through dry merging. The massive quiescent galaxies at higher redshift become flatter, and are as flat as SF massive galaxies at 2.5<z<3.5, consistent with formation through direct transformations or wet mergers. Find that in quiescent galaxies, correlations with q_med and M*, z and r_e are driven by the evolution in the sersic index (n), consistent with the growing accumulation of minor mergers at lower redshift. Interestingly, n does not drive these trends fully in SF galaxies. Instead, the strongest predictor of q in SF galaxies is the effective radius, where larger galaxies are flatter. Findings suggest that q_med is tracing bulge-to-total (B/T) galaxy ratio which would explain why smaller/more massive SF galaxies are rounder than their extended/less massive analogues, although it is unclear why sersic index correlates more weakly with flattening for SF galaxies than fore quiescent galaxies.
1901.02014
Prospects for observing strongly lensed supernovae behind Hubble Frontier Fields galaxy clusters with the James Webb Space Telescope
Petrushevska, et al
Measuring time delays from strongly lensed SNe is emerging as a novel and independent tool for estimating the Hubble constant H0. This is very important given the recent discord in the value of H0 from two methods that probe different distance ranges. The success of this technique will rely on the ability to discover strongly lensed SNe with measurable time delays. Here, present the magnifications and the time delays for the multiply-imaged galaxies behind the Hubble Frontier Fields (HFF) galaxy clusters, by using recently published lensing models. Continuing on the previous work done for A1689 and A370, also show the prospects of observing strongly lensed SNe behind the HFF clusters with the upcoming JWST. With four 1 hr visits in one year, the summed expectations of all six HFF clusters are ~0.5 core-collapse SNe and ~0.06 SNe Ia in F115W band, while with F150W the expectations are higher, ~0.9 CC SNe and ~0.06 SNe Ia. These estimates match those expected by only surveying A1689, proving that the performance of A1689 as gravitational telescope is superior. In the five HFF clusters presented here, find that F150W will be able to detect SNe Ia (SNe IIP) exploding in 93 (80) pairs multiply-imaged galaxies with time delays of less than 5 years.
1901.02267
Extremely massive quasars are not good proxies for dense environments compared to massive galaxies: environments of extremely massive quasars and galaxies
Yoon, et al
BH mass scaling relations suggest that extremely massive black holes (EMBHs) with M_BH>=1e9.4 Msun are found in the most massive galaxies with M* >= 1e11.6 Msun, which are commonly found in dense environments, like galaxy clusters. Therefore, one can expect that there is a close connection between active EMBHs and dense environments. Here, study the environments of 9461 galaxies and 2943 quasars at 0.24 <= z <= 0.4, among whichh 52 are extremely massive quasars with log(M_BH/Msun) >=9.4, using SDSS and MMT Hectospec data. Find that, on average, both massive quasars and massive galaxies reside in environments more than ~2x as dense as those of their less massive counterparts with log(M_BH/Msun)>=9.0. However, massive quasars reside in environments about half as dense as inactive galaxies with log(M_BH/Msun) >= 9.4, and only about one third of massive quasars are found in galaxy clusters, while about 2/3 of massive galaxies reside in such clusters. This indicates that massive galaxies are a much better signpost for galaxy clusters than massive quasars. The prevalence of massive quasars in moderate to low density environments is puzzling, considering that several simulation results show that these quasars appear to prefer dense environments. Several possible reasons for this discrepancy are discussed, although further investigation is needed to obtain a definite explanation.
1901.02269
Dark matter response to galaxy assembly history
Artale, et al
Aims: it is well known that the presence of baryons affects the DM host haloes. Exploring the galaxy assembly history together with the DM haloes properties through time can provide a way to measure these effects. Methods: Study the properties of 4 MW mass DM haloes from the Aquarius project during their assembly history, between z=0-4. In this work, use the SPH run from Scannapieco+2009 and the DM only counterpart as case studies. To asses the robustness of the findings, compare them with one of the haloes run using a moving-mesh technique and different sub-grid scheme. Results: the results show that the cosmic evolution of the DM halo profiles depends on the assembly history of the baryons. Find that the DM profiles do not significantly change with time, hence they become stable, when the fraction of baryons accumulated in the central regions reaches 80 percent of its present mass within the viral radius. Furthermore, the mass accretion history shows that the haloes that assembly earlier are those that contain a larger amount of baryonic mass aforetime, which in turn allows the DM halo profiles to reach a stable configuration earlier. For the SPH haloes, find that the specific angular momentum of the DM particles within the 5% of the viral radius at z=0, remains approximately constant from the time at which 60% of the stellar mass is gathered. Explore different theoretical and empirical models for the contraction of the haloes through z. A model to better describe the contraction of the haloes through z evolution must depend on the stellar mass content in the inner regions.
1901.02301
Bifurcation in the growth of continental crust
Höning, et al
Is the present-day water-land ratio a necessary outcome of the evolution of plate tectonic planets with a similar age, volume, mass and total water inventory as the Earth? This would be the case - largely independent of initial conditions - if Earth's present-day continental volume were at a stable unique equilibrium with strong self-regulating mechanisms of continental growth steering the evolution to this state. In this paper, this conjecture is questioned. Instead, suggest that positive feedbacks in the plate tectonics model of continental production and erosion may dominate and show that such a model can explain the history of continental growth. Investigate the main mechanisms that contribute to the growth of the volume of the continental crust. In particular, analyze the effect of the oceanic plate speed, depending on the area and thickness of thermally insulating continents, on production and erosion mechanisms. Effects that cause larger continental production rates for larger values of continental volume are positive feedbacks. In contrast, negative feedbacks act to stabilize the continental volume. They are provided by the increase of the rate of surface erosion, subduction erosion, and crustal delamination with the continental volume. Systematically analyze the strengths of positive and negative feedback contributions to the growth of the continental crust. Although the strengths of some feedbacks depend on poorly known parameters, conclude that a net predominance of positive feedbacks is plausible. Explore the effect of the combined feedback strength on the feasibility of modeling the observed small positive net continental growth rate over the past 2-3 billion years.
1901.02400
Can the homogeneity scale be used as a standard ruler?
Nesseris, Trashorras
Demonstrate that the answer is clearly negative.
1901.02578
Overview of initial results from the reconnaissance flyby of a Kuiper Belt planetesimal: 2014 MU69
Stern, et al
The centerpiece objective of the NASA New Horizons first Kuiper Extended Mission (KEM-1) was the close flyby of the KBO 2014 MU69, nicknamed Ultima Thule. On 1 Jan 2019 this flyby culminated, making the first close observations of a small KBO. Initial post flyby trajectory reconstruction indicated the spacecraft approached to within 3536 km of MU69 at 5:33:19 UT. Here, summarize the earliest results obtained from that successful flyby. At the time of this submission, only 4 days of data down-link from the flyby were available; well over an order of magnitude more data will be down-linked by the time of this Lunar and Planetary Science Conference presentation in 2019 March. Therefore many additional results not available at the time of this abstract submission will be presented in this review talk.
1901.02542
Asteroids detection technique: classic "Blink" an automated approach
Copandean, et al
Asteroids detection is a very important research field that received increased attention in the least couple of decades. [...] ...obtain their results in a visual manner: they "blink" a sequence of reduced images of the same field, taken at a specific time interval, and they try to detect a real moving objection the resulting animation. Such a technique becomes harder with the increase in size of the CCD cameras. Aiming to replace manual detection, propose an automated "blink" technique for asteroids detection.
1901.02568
The impact of environment on late time evolution of the stellar mass - halo mass relation
Golden-Marx, Miller
At a fixed halo mass, galaxy clusters with higher magnitude gaps have larger BCG stellar masses. Recent studies have shown that by including the magnitude gap (m_gap) as a latent parameter in the stellar mass - halo mass (SMHM) relation, we can make more precise measurement on the amplitude, slope, and intrinsic scatter. Using galaxy clusters from SDSS, measure the SMHM-m_gap relation and its evolution out to z=0.3. Using a fixed comoving aperture of 100 kpc to define the central galaxy's stellar mass, report statistically significant negative evolution in the slope of the SMHM relation to z=0.3 (>3.5 sigma). The steepening of the slope over the last 3.5 Gyrs can be explained by late-time merger activity at the cores of galaxy clusters. Also find that the inferred slope depends on the aperture used to define the radial extent of the central galaxy. At small radii (20 kpc), the slope of the SMHM relation is shallow, indicating that the core of the central galaxy is less related to the growth of the underlying host halo. By including all of the central galaxy's light within 100 kpc, the slope reaches an asymptote at a value consistent with recent high resolution hydrodynamical cosmology simulations.
1901.02576
First detection of the pre-biotic molecule glycolonitrile (HOCH2CN) in the interstellar medium
Zeng, et al
Theories of a pre-RNA world suggest that glycolonitrile (HOCH_2CN) is a key species in the process of ribonucleotide assembly, which is considered as a molecular precursor of nucleic acids. In this Letter, report the first detection of this pre-biotic molecule in the interstellar medium (ISM) by using ALMA data obtained at frequencies between 86.5 GHz and 266.5 GHz toward the Solar-type protostar IRAS16293-2422 B. A total of 15 unblended transitions of HOCH_2CN were identified. The analysis indicates the presence of a cold (T_ex = 24±8 K) and a warm (T_ex = 158±38 K) component meaning that this molecule is present in both the inner hot corino and the outer cold envelope of IRA16293 B. The relative abundance with respect to H2 is (6.5±0.6)e-11 and >=(6±2)e-10 for the warm and cold components respectively. The chemical modeling seems to underproduce the observed abundance for both the warm and cold component under various values of the cosmic-ray ionization rate (zeta). Key gas phase routes for the formation of the molecule might be missing in the chemical network.
1901.02724
Can HI gas trace the matter density distribution linearly on large scales?
Wang, et al
It is customary to assume that HI gas traces the matter density distribution linearly on large scales. However, nonlinear effects which modulate HI gas in haloes might spoil this. Employ three approaches to generate the mock HI density from an N-body simulation at low redshifts, and demonstrate, for the first time, that the HI linearity assumption breaks down at k>0.1 h/Mpc, generically, except for a "sweet-spot" redshift near z=1.2. In addition, the HI bias scales approximately linearly with redshift for z<=3. The founding are independent of models.
1901.02850
Ultima Thule: a prediction for the origin, bulk chemical composition, and physical structure, submitted prior to the new horizons spacecraft 100 Pixel LORRI data return
Prentice
The 2019 January 01 flypast of Ultima Thule by the New Horizons spacecraft has provided the author with a new opportunity to test his gas ring model of planetary origin (Prentice, 1978). The model proposes that Ultima Thule condensed from the first gas ring shed by the gravitationally contracting protosolar cloud. Use the fully quantified gas ring model to compute the thermal properties of the gas ring in which Ultima condensed and thence to predict the initial bulk chemical composition of the condensate. It is predicted that all KBOs initially constrained large stores of CO2 ice and CH4 ices. These make up fractions 0.2210 and 0.513 of the condensate mass, respectively. Water ice makes up a mass fraction 0.1845, nearly-dry rock has fraction 0.5269 and graphite has 0.0163. Next, compute the thermal evolution of Ultima, taking into account the radiogenic heat released by the decay of 26Al. Stellar occultation data suggest that Ultima Thule may consist of 2 lobes of radius about 10 km and 7.5 km. The thermal evolution model shows that within 0.2 Myr, the peak internal temperatures are sufficient for a fraction ~0.7 of the CH4 ice in the larger lobe to melt and for a fraction ~0.4 of the CO2 ice to sublime. For the smaller lobe, these fractions are less. Liquid CH4 quickly migrates upwards to the surface and refreezes to form a thick outer shell of CH4 ice. The sublimation of CO2 takes place after the melting of CH4. The possibility now exists for rising CO2 vapor to become trapped beneath the CH4 shell. This may lead to explosive eruptions of the outer shell and destruction of the primordial surface of Ultima and loss of the CO2. If 60% of CO2 is lost, the lobe radii each shrinks by ~5%. Even so, the intensity of 26Al radiogenic heating may not be sufficient to render the surface of Ultima Thule globally smooth, unless the lobe sizes are of order ~15km.
1901.02897
Climate sensitivity to ozone and its relevance on the habitability of Earth-like planets
Gomez-Leal, et al
Show that the warming effect of ozone increases both the humidity of the lower atmosphere and the surface temperature.
1901.02900 ***
The birth of the Milky Way: the in-situ halo and early thick disk as uncovered by accurate stellar ages with Gaia
Gallart et al
As MW-like galaxies form, smaller stellar systems accrete onto the main galactic progenitor, assembling a kinematically hot spheroidal-like stellar halo surrounding the galactic disc. There is extensive observational evidence of this merging process both in the MW and in external galaxies. However, unambiguously identifying the oldest stellar population formed in the MW main progenitor has remained elusive, as a good fraction of observed stars in our Galactic halo have characteristics pointing to an external origin. In this paper, unveil the old stellar population that can be associated with the first star formation events in the MW. Identify this population with the red sequence of the enigmatic, double sequenced color-magnitude diagram (CMD) of the kinematically hot, halo stars discovered in the second data release of the Gaia mission. This discovery results from the novel, robust determination of stellar age distributions in the thick disc and halo Gaia CMDs, using the well established technique of CMD modeling, and the comparison with state-of-the-art cosmological simulations of galaxy formation. The age distributions unambiguously show that the stars in the blue and red sequences of the halo CMD are equally old, and older than the bulk of thick disc stars. This evidence allows us the identify the red sequence as the 'in-situ' halo stars, formed within the seed progenitor of our MW. The in-situ halo is naturally more metal rich than the accreted halo population originating in the lower-mass galaxy Gaia-Enceladus whose stars form most of the blue sequence. These findings provide a crystal clear picture of the early sequence of events that gave rise to the complex MW structure, and have far reaching implications for understanding the formation of disc galaxies in general.
1901.02901
Climate sensitivity to carbon dioxide and moist greenhouse threshold of Earth-like planets under an increasing solar forcing
Gomez-Leal, et al
CO2 is one of the major contributors to the radiative forcing, increasing both the temperature and the humidity of Earth's atmosphere. If the stellar irradiance increases and water becomes abundant in the stratosphere of an Earth-like planet, it will be dissociated and the resultant hydrogen will escape from the atmosphere. This state is called the moist greenhouse threshold (MGT). Using a global climate model (GCM) of intermediate complexity, explore how to identify this state for different CO2 concentrations and including the radiative effect of atmospheric ozone for the first time. Show that the moist greenhouse threshold correlates with the inflection point in the water vapor mixing ratio in the stratosphere and a peak in the climate sensitivity. For CO2 concentrations between 560 ppm an 200 ppm, the moist greenhouse threshold is reached at a surface temperature of 320K. Despite the higher simplicity of the model, the results are consistent with similar simulations without ozone by complex GCMs, suggesting that they are robust indicators of the MGT. Discuss the implications for inner edge of the habitable zone as well as the water loss timescales for Earth analog planets.
1901.03156
Galaxies with monstrous black holes in galaxy cluster environments
van Son, et al
Massive early-type galaxies follow a tight relation between the mass of their central SMBH (M_BH) and their stellar mass (M*). The origin of observed positive outliers from this relation with extremely high M_BH (>1e9 Msun) remains unclear. Present a study of such outliers in the Hydrangea/C-EAGLE cosmo hydro sims, designed to enable the study of high-mass galaxy formation and evolution in cluster environments. Find 69 M_BH(M*) outliers at z=0, defined as those with M_BH>1e7 Msun and M_BH/M*>0.01. This paper focusses on a sample of 5 extreme outliers, that have been selected based on their M_BH and M* values, which are comparable to the most recent estimates of observed positive outliers. This sample of 5 outliers, classified as Black hole monster galaxies (BMGs), was traced back in time to study their origin and evolution. In agreement with the results of previous simulations for lower-mass M_BH(M*) outliers, find that these galaxies became outliers due to a combination of their early formation times and tidal stripping. For BMGs with M_BH>1e9 MSun, major mergers (with a stellar mass ratio of mu>0.25) at early times (z>2) precede the rapid growth of their SMBH. Furthermore, the scatter in the relation between M_BH and stellar velocity dispersion, sigma, correlates positively with the scatter in [Mg/Fe](sigma). This indicates that the alpha enhancement of these galaxies, which is closely related to their star formation history, is related to the growth of their central BHs.
1901.03190 ***
Twin LIGO/Virgo detections of a viable gravitationally-lensed black hole merger
Broadhurst, et al
Identify a binary black hole (BBH) merger that appears to be multiply lensed by an intervening galaxy. The LIGO/Virgo events GW190809 and GW190814 have indistinguishable waveforms separated by 5 days, and overlap on the sky within the 90% credible region. Their strain amplitudes are also similar, implying a modest relative magnification ratio, as expected for a pair of lensed gravitational waves. The phase of the two events is also consistent with being the same, adding more evidence in support of both events originating from the same BBH merger. The difference in the published inferred distances of each event can then be interpreted as following from their different magnifications. The observed chirp masses of both events are also similar, as expected for a pair of lensed events, with a common detected values of 29.1+1.3-1.0 Msun, lying at the peak of the observed distribution of chirp masses. Infer this case as a prototypical example of a lensed event that supports the lensing prediction (Broadhurst 2018) according to which, cosmologically distant, magnified BBH comprise most of the LIGO/Virgo events with chirp masses enhanced above ~=15 Msun by the cosmological expansion. From the predictions, estimate an intrinsic, unlicensed, chirp mass of ~=10-12 Msun, with a source redshift in the range 0.9<z<2.5. Also outline a joint analysis over all baseline permutations that can stringently test the lensing interpretation of these two events. More generally, lensed events effectively multiply the number of baseline permutations and motivates the use of more interferometers for round the clock coverage of all repeat events of a given source, in order to maximize the orbital details and sky localization of lensed BBH sources.
1901.03336
Disruption of satellite galaxies in simulated groups and clusters: the roles of accretion time, baryons, and pre-processing
Bahé, et al
Investigate the disruption of group and cluster satellite galaxies with total mass (DM plus baryons) above 1e10 Msun in the Hydrangea simulations, a suite of 24 high-res cosmo hydro zoom-in sims based on the EAGLE model. The simulations predict that ~50% of satellites survive to z=0, with higher survival fractions in massive clusters than in groups and only small differences between baryonic and pure N-body simulations. For clusters, up to 90% of galaxies disruption occurs in lower-mass sub-groups (i.e., during pre-processing); 96% of satellites in massive clusters that were accreted at z<2 and have not been pre-processed survive. Of those satellites that are disrupted, only a few % merge with other satellites, even in low-mass groups. The survival fraction changes rapidly from less than 10% of those accreted at high z to more than 90% at low z. This shift, which reflects faster disruption of satellites accreted at higher z, happens at lower z for more massive galaxies and those accreted onto less massive haloes. The disruption of satellite galaxies is found to correlate only weakly with their pre-accretion baryon content, SFR, and size, so that surviving galaxies are nearly unbiased in these properties. These results suggest that satellite disruption in massive haloes is uncommon, and that it is predominantly the result of gravitational rather than baryonic processes.
1901.03338
A new view on Auger data and cosmogenic neutrinos in light of different nuclear disintegration and air-shower models
Heinze, et al
Study the implications of UHECR data from the Pierre Auger Observatory for potential accelerator candidates and cosmogenic neutrino fluxes for different combinations of nuclear disintegration and air-shower models. Exploit the most recent spectral and mass composition data (2017) with new, computationally very efficient simulation code PriNCe. Extend the systematic framework originally developed by the Pierre Auger Collaboration with the cosmo source evolution as an additional free parameter. In this framework, an ensemble of generalized UHECR accelerators is characterized by a universal spectral index (equal for all injection species), a maximal rigidity, and the normalizations for five nuclear element groups. Find that the 2017 data favor a small but constrained contribution of heavy elements (Fe) at the source. Demonstrate that the results moderately depend on the nuclear disintegration (PSB, Peanut, or Talys) model, and more strongly on the air-shower (EPOS-LHC, Sibyll-2.3, or QGSjet-II-04) model. Variations of these models result in different source evaluations and spectral indices, limiting the interpretation in terms of a particular class of cosmic accelerators. Better constrained parameters include the maximal rigidity and the mass composition at the source. Hence, the cosmogenic neutrino flux can be robustly predicted, since it originates from interactions with the cosmic infrared background and peaks at 1e8 GeV. Depending on the source evolution at high redshifts the flux is likely out of reach of future neutrino observatories in most cases, and a minimal cosmogenic neutrino flux cannot be claimed from data without assuming a cosmological distribution of the sources.
1901.03341
An upper limit on primordial magnetic fields from ultra-faint dwarf galaxies
Safarzadeh, Loeb
The presence of primordial magnetic fields increases the minimum halo mass in which star formation is possible at high z. Estimates of the dynamical mass of ultra-faint dwarf galaxies (UFDs) within their half-light radius constrain their virtualized halo mass before their infall into the MW. The inferred halo mass and formation redshift of the UFDs place upper bounds on the primordial comoving magnetic field, B0. Derive an upper limit of 0.40±0.086 (0.31±0.04) nG on B0~assuming the average formation redshift of the UFD host haloes is z_form=10(20), respectively.
1901.03344
Constraining first star formation with 21cm-Cosmology
Schauer, et al
Within standard LCDM cosmology, Pop III star formation in mini haloes of mass M_halo >~5e5 Msun provides the first stellar sources of Lyman alpha photons. The Experiment to Detect the Global Epoch of Reionization Signature (EDGES) has measured a strong absorption signal of the redshifted 21 cm radiation from neutral H at z~17, requiring efficient formation of massive stars before then. In this paper, investigate whether SF in mini haloes plays a significant role in establishing the early Ly-a background required to produce the EDGES absorption feature. Find that Pop III stars are important in providing the necessary Ly-a-flux at high zs, and derive a best-fitting average Pop III stellar mass of ~120 Msun per minimal. Further, it is important to include baryon-DM streaming velocities in the calculation, to limit the efficiency of Pop-III star formation in mini haloes. Without this effect, the cosmic dawn coupling between 21 cm spin temperature and that of the gas would occur at z higher than what is implied by EDGES.
1901.03485
The analysis of effective galaxies number count for Chinese Space Station Optical Survey (CSS-OS) by image simulation
Zhang, et al
CSS-OS is a mission to explore the vast universe. This mission will equip a 2-m space telescope to perform a multi-band NUV-opitcal large area survey (over 40% of the sky) and deep survey (~1% of the sky) for the cosmological and astronomical goals. Galaxy detection is one of the most important methods to achieve scientific goals. In this paper, evaluate the galaxy number density for CSS-OS in i band (depth, i~26 for large area survey and ~27 for the deep survey), point source, 5-sigma by the method of image simulation. Also compare galaxies detected by CSS-OS with that of LSST (i~27, point source, 5-sigma). In the simulation, the HUDF galaxy catalogs are used to create mock images due to long enough integration time which meets the completeness requirements of the galaxy analysis for CSS-OS and LSST. The galaxy surface profile and spectrum are produced by the morphological information, photometric z and SEDs from the catalogs. The instrumental features and the environmental condition are also considered to produce the mock galaxy images. The galaxies of CSS-OS and LSST are both extracted by SExtractor from the mock i band image and matched with the original catalog. Through the analysis of the extracted galaxies, find that the effective galaxy number count is ~13 arcmin^-2, ~40 arcmin^-2 and ~42 arcmin^-2 for CSS-OS large area, CSS-OS deep, and LSST, respectively. Moreover, CSS-OS shows the advantage in small galaxy detection with high spatial resolution, especially for the deep survey: about 20% of the galaxies detected by CSS-OS deep survey are not detected by LSST, and they have a small effective radius of re<0.3".
1901.03569
First cryogenic test operation of underground km-scale gravitational-wave observatory KAGRA
KAGRA Collaboration, et al
KAGRA is a second-generation interferometric gravitational-wave detector with 3-km arms constructed at Kamioka, Gifu in Japan. It is now in its final installation phase, which is called bKAGRA (baseline KAGRA), with scientific observations expected to begin in late 2019. One of the advantages of kAGRA is its underground location of at least 200m below the ground surface, which brings small seismic motion at low frequencies and high stability of the detector. Another advantage is that it cools down the sapphire test mass mirrors to cryogenic temperatures to reduce thermal noise. In April-May 2018, operated a 3-km Michelson interferometer with a cryogenic test mass for 10 days, which was the first time that km-scale interferometer was operated at cryogenic temperatures. In this article, report the results of this "bKAGRA Phase 1" operation. Demonstrated the feasibility of 3-km interferometer alignment and control with cryogenic mirrors.
1901.03609
Escape of cosmic rays from the Galaxy and effects on the circumgalactic medium
Blasi, Amato
The escape of cosmic rays from the Galaxy is expected to shape their spectrum inside the Galaxy. Yet, this phenomenon is very poorly understood and, in the absence of a physical description, it is usually modeled as free escape from a given boundary, typically located at a few kpc distance from the Galactic disc. Show that the assumption of free escape leads to the conclusion that the CR current propagating in the circumgalactic medium is responsible for a non resonant CR induced instability that in turn leads to the generation of a magnetic field of strength ~2e-8 Gauss on a scale ~10kpc around our Galaxy. The self-generated diffusion produces large gradients in the particle pressure that induce a displacement of the intergalactic medium with velocity ~10-100 km/s. CRs are then carried away by advection. If the over density of the intergalactic gas in a region of size ~10 kpc around our Galaxy is >~100 with respect to the cosmological baryon density Omega_b rho_cr, then the flux of high energy neutrinos as due to pion production becomes comparable with the flux of astrophysical neutrinos recently measured by IceCube.
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