Search

The Balmer decrement (H$\alpha$/H$\beta$) provides a constraint on attenuation, the cumulative effects of dust grains in the ISM. The ratio is a reliable spectroscopic tool for deriving the dust properties of galaxies that determine many different quantities such as star formation rate, metallicity, and SED models. Here we measure independently both the attenuation and H$\alpha$/H$\beta$ of an occulting galaxy pair: VV 191. Attenuation measurements in the visible spectrum (A$_{V,stars}$) from dust maps derived from the F606W filter of HST and the F090W filter of JWST are matched with spaxel-by-spaxel H$\alpha$/H$\beta$ observations from the George and Cynthia Mitchell Spectrograph (GCMS) of the McDonald Observatory. The 0.5 to 0.7 micron bandpass covers the Balmer lines for VV 191. The dust maps of JWST and HST provide the high sensitivity necessary for comparisons and tracking trends of the geometrically favorable galaxy. We present maps and plots of the Balmer lines for the VV 191 galaxy pair and for a specific region highlighting dust lanes for VV 191b in the overlap region. We compute A$_{V, HII}$ from H$\alpha$/H$\beta$ and plot both quantities against A$_{V, stars}$. Our results show that regions with higher dust content, residing closer to the spiral center, dominate ionized gas attenuation, leading to an overestimation of A$_{V, HII}$ by a factor or 2. Further out in the spiral arms, the lower dust content leads to more agreement between the attenuations, indicating lower SFR and larger contribution from older stars to the stellar continuum outside the Petrosian radius., Comment: 21 pages, 14 figures, 2 tables, accepted for publication by The Astronomical Journal

Groups of galaxies are the intermediate density environment in which much of the evolution of galaxies is thought to take place. In spectroscopic redshift surveys, one can identify these as close spatial redshift associations. However, spectroscopic surveys will always be more limited in luminosity and completeness than imaging ones. Here we combine the Galaxy And Mass Assembly group catalogue with the extended Satellites Around Galactic Analogues (xSAGA) catalogue of Machine Learning identified low-redshift satellite galaxies. We find 1825 xSAGA galaxies within the bounds of the GAMA equatorial fields (m < 21), 1562 of which could have a counterpart in the GAMA spectroscopic catalogue (m < 19.8). Of these, 1326 do have a GAMA counterpart with 974 below z=0.03 (true positives) and 352 above (false positives). By crosscorrelating the GAMA group catalogue with the xSAGA catalogue, we can extend and characterize the satellite content of GAMA galaxy groups. We find that most groups have <5 xSAGA galaxies associated with them but richer groups may have more. Each additional xSAGA galaxy contributes only a small fraction of the group's total stellar mass (<<10%). Selecting GAMA groups that resemble the Milky Way halo, with a few (<4) bright galaxies, we find xSAGA can add a magnitude fainter sources to a group and that the Local Group does not stand out in the number of bright satellites. We explore the quiescent fraction of xSAGA galaxies in GAMA groups and find a good agreement with the literature., Comment: 11 pages, 13 Figures, 2 Tables, accepted by MNRAS

Background: In stars, carbon is produced exclusively via the $3\alpha$ process, where three $\alpha$ particles fuse to form $^{12}$C in the excited Hoyle state, which can then decay to the ground state. The rate of carbon production in stars depends on the radiative width of the Hoyle state. The radiative width can be deduced by combining three separately measured quantities, one of which is the $E0$ decay branching ratio. The $E0$ branching ratio can be measured by exciting the Hoyle state in the $^{12}$C$(p,p')$ reaction and measuring the pair decay of its Hoyle state and first $2^+$ state. Purpose: To reduce the uncertainties in the carbon production rate in the universe by measuring a set of proton angular distributions for the population of the Hoyle state ($0^+_2$) and $2^+_1$ state in $^{12}$C in $^{12}$C$(p,p')$ reactions between 10.20 and 10.70 MeV, used in the determination of the $E0$ branching ratio of the Hoyle state. Method: Proton angular distributions populating the ground, first $2^+$, and the Hoyle states in $^{12}$C were measured in $^{12}$C(p,p') reactions with a silicon detector array covering $22^\circ<\theta<158^\circ$ in 14 energy steps between 10.20 and 10.70 MeV with a thin ($60\ \mu$g/cm$^2$) $^{nat}$C target. Results: Total cross-sections for each state were extracted and the population ratio between the $2^+_1$ and Hoyle state determined at each energy step. By appropriately averaging these cross-sections and taking their ratio, the equivalent population ratio can be extracted applicable for any thick $^{12}$C target used in pair-conversion measurements. Conclusions: We present a general data set of high-precision $^{12}$C$(p,p')$ cross-sections that make uncertainties resulting from the population of the $2^+_1$ and $0^+_2$ states by proton inelastic scattering negligible for any future measurements of the $E0$ branching ratio in $^{12}$C., Comment: 11 pages, 7 figures

Vermont passed universal prekindergarten (preK) legislation in 2014 (Act 166) in an effort to increase access to quality preK programs for all young children in the state. Act 166 provides state funded preK to all olds (and to 5 year olds who are not eligible for kindergarten). Families can enroll their children at no cost in any prequalified preK program across the state regardless of location. To better understand implementation of Act 166, Vermont requested a study that describes the relationship between the characteristics and location of preK children and their enrollment by type of preK program (public school program within or outside the boundaries of a child's local education agency and private childcare center or family childcare home within or outside the boundaries of a child's local education agency) and state assessed program quality. The study found that in 2016/17, the first year of full implementation, preK children with an individualized education program and children eligible for the national school lunch program were more likely than their counterparts to be enrolled in a public school program and in a program with a higher quality rating. While most children were enrolled in a program within the boundaries of their local education agency, that was more likely for children with an individualized education program and children eligible for the national school lunch program. This study brief presents an overview of the study. [For the full report, see ED602006; for the appendixes, see ED602009; and for the study snapshot, see ED602008.]

A challenge preventing successful inverse kinematics measurements with heavy nuclei that are not fully stripped is identifying and tagging the beam particles. For this purpose, the HEavy ISotope Tagger (HEIST) has been developed. HEIST utilizes two micro-channel plate timing detectors to measure time of flight, a multi-sampling ion chamber to measure energy loss, and a high purity Ge detector to identify isomer decays and calibrate the isotope identification system. HEIST has successfully identified $^{198}$Pb and other nearby nuclei at energies of about 75 MeV/A. In the experiment discussed, a typical cut containing 89\% of all $^{198}$Pb$^{+80}$ in the beam had a purity of 86\%. We examine the issues of charge state contamination. The observed charge state populations of these ions are presented and are moderately well described by the charge state model GLOBAL., Comment: The following article has been submitted to Review of Scientific Instruments

Stellar carbon synthesis occurs exclusively via the $3\alpha$ process, in which three $\alpha$ particles fuse to form $^{12}$C in the excited Hoyle state, followed by electromagnetic decay to the ground state. The Hoyle state is above the $\alpha$ threshold, and the rate of stellar carbon production depends on the radiative width of this state. The radiative width cannot be measured directly, and must instead be deduced by combining three separately measured quantities. One of these quantities is the $E0$ decay branching ratio of the Hoyle state, and the current $10$\% uncertainty on the radiative width stems mainly from the uncertainty on this ratio. The $E0$ branching ratio was deduced from a series of pair conversion measurements of the $E0$ and $E2$ transitions depopulating the $0^+_2$ Hoyle state and $2^+_1$ state in $^{12}$C, respectively. The excited states were populated by the $^{12}$C$(p,p^\prime)$ reaction at 10.5 MeV beam energy, and the pairs were detected with the electron-positron pair spectrometer, Super-e, at the Australian National University. The deduced branching ratio required knowledge of the proton population of the two states, as well as the alignment of the $2^+_1$ state in the reaction. For this purpose, proton scattering and $\gamma$-ray angular distribution experiments were also performed. An $E0$ branching ratio of $\Gamma^{E0}_{\pi}/\Gamma=8.2(5)\times10^{-6}$ was deduced in the current work, and an adopted value of $\Gamma^{E0}_{\pi}/\Gamma=7.6(4)\times10^{-6}$ is recommended based on a weighted average of previous literature values and the new result. The new recommended value for the $E0$ branching ratio is about 14% larger than the previous adopted value of $\Gamma^{E0}_{\pi}/\Gamma=6.7(6)\times10^{-6}$, while the uncertainty has been reduced from 9% to 5%., Comment: Accepted for publication as a Regular Article in Phys. Rev. C on July 29 2020

Tracking capabilities in Time Projection Chambers (TPCs) are strongly dictated by the homogeneity of the drift field. Ion back-flow in various gas detectors, mainly induced by the secondary ionization processes during amplification, has long been known as a source of drift field distortion. Here, we report on beam-induced space-charge effects from the primary ionization process in the drift region in low-energy nuclear physics experiment with Active Target Time Projection Chamber (AT-TPC). A qualitative explanation of the observed effects is provided using detailed electron transport simulations. As ion mobility is a crucial factor in the space-charge effects, the need for a careful optimization of gas properties is highlighted. The impact of track distortion on tracking algorithm performance is also discussed.

Energy dissipative processes play a key role in how quantum many-body systems dynamically evolve towards equilibrium. In closed quantum systems, such processes are attributed to the transfer of energy from collective motion to single-particle degrees of freedom; however, the quantum many-body dynamics of this evolutionary process are poorly understood. To explore energy dissipative phenomena and equilibration dynamics in one such system, an experimental investigation of deep-inelastic and fusion-fission outcomes in the $^{58}$Ni+$^{60}$Ni reaction has been carried out. Experimental outcomes have been compared to theoretical predictions using Time Dependent Hartree Fock and Time Dependent Random Phase Approximation approaches, which respectively incorporate one-body energy dissipation and fluctuations. Excellent quantitative agreement has been found between experiment and calculations, indicating that microscopic models incorporating one-body dissipation and fluctuations provide a potential tool for exploring dissipation in low-energy heavy ion collisions., Comment: 11 pages, 9 figures, 1 table, including Supplemental Material - Version accepted for publication in Physical Review Letters

The atomic numbers and the masses of fragments formed in quasi-fission reactions have been simultaneously measured at scission in 48 Ti + 238 U reactions at a laboratory energy of 286 MeV. The atomic numbers were determined from measured characteristic fluorescence X-rays whereas the masses were obtained from the emission angles and times of flight of the two emerging fragments. For the first time, thanks to this full identification of the quasi-fission fragments on a broad angular range, the important role of the proton shell closure at Z = 82 is evidenced by the associated maximum production yield, a maximum predicted by time dependent Hartree-Fock calculations. This new experimental approach gives now access to precise studies of the time dependence of the N/Z (neutron over proton ratios of the fragments) evolution in quasi-fission reactions., Comment: 6 pages, 5 figures, accepted for publication in Phys.Rev.Lett

Background: Formation of a fully equilibrated compound nucleus is a critical step in the heavy-ion fusion reaction mechanism but can be hindered by orders of magnitude by quasifission, a process in which the dinuclear system breaks apart prior to full equilibration. To provide a complete description of heavy-ion fusion it is important to characterize the quasifission process. In particular, the impact of changing the neutron-richness of the quasifission process is not well known. A previous study of Cr + W reactions at a constant 13 % above the Coulomb barrier concluded that an increase in neutron-richness leads to a decrease in the prominence of the quasifission reaction channel. Purpose: The interplay between the fusion-fission and quasifission reaction channels, with varying neutron-richness, was explored at a constant excitation energy, closer to the interaction barrier than the previous work, to see if the correlation between neutron-richness and quasifission is valid at lower energies. Methods: Mass distributions were determined for eight different combinations of Cr + W reactions at the Australian National University at 52.0 MeV of excitation energy in the compound nucleus. Results: A curvature parameter was determined for the fission-like fragment mass distributions and compared to various reaction parameters known to influence quasifission. Conclusions: The present work demonstrates that at energies near the interaction barrier the deformation effects dominate over the neutron-richness effects in the competition between quasifission and compound nucleus formation in these Cr + W systems and is an important consideration for future with heavy and superheavy element production reactions.

Complete fusion cross sections in collisions of light, weakly bound nuclei and high Z targets show above-barrier suppression of complete fusion. This has been interpreted as resulting from breakup of the weakly bound nucleus prior to reaching the fusion barrier, reducing the probability of complete fusion. This paper investigates how these conclusions are affected by lifetimes of the resonant states that are populated prior to breakup. If the mean life of a populated resonance is much longer than the fusion timescale, then its breakup cannot suppress complete fusion. For short-lived resonances, the situation is more complex. This work includes the mean life of the short-lived 2+ resonance in 8Be in classical dynamical model calculations to determine its effect on energy and angular correlations of the breakup fragments and on predictions of fusion suppression. Coincidence measurements of breakup fragments produced in reactions of 9Be with 144Sm, 168Er, 186W, 196Pt, 208Pb and 209Bi at energies below the barrier are re-analysed. Predictions of breakup observables and of complete and incomplete fusion at energies above the fusion barrier are made using the classical dynamical simulation code PLATYPUS, modified to include the lifetimes of short-lived resonant states. The agreement of the breakup observables is improved when lifetime effects are included. The predicted suppression of complete fusion due to breakup is nearly independent of Z, with an average value of 9%, below the experimentally determined fusion suppression of 30% in these systems. This more realistic treatment of breakup leads to the conclusion that the suppression of complete fusion cannot be fully explained by breakup prior to reaching the fusion barrier. Other mechanisms that can suppress complete fusion must be investigated. A candidate is cluster transfer that produces the same nuclei as incomplete fusion., Comment: 16 pages, 10 figures. Accepted as a Regular Article in Physical Review C

Measurements of mass-angle distributions (MADs) for Cr + W reactions, providing a wide range in the neutron-to-proton ratio of the compound system, (N/Z)CN, have allowed for the dependence of quasifission on the (N/Z)CN to be determined in a model-independent way. Previous experimental and theoretical studies had produced conflicting conclusions. The experimental MADs reveal an increase in contact time and mass evolution of the quasifission fragments with increasing (N/Z)CN, which is indicative of an increase in the fusion probability. The experimental results are in agreement with microscopic time-dependent Hartree-Fock calculations of the quasifission process. The experimental and theoretical results favor the use of the most neutron-rich projectiles and targets for the production of heavy and superheavy nuclei., Comment: Accepted to PRC as a Rapid Communication

The Taiwanese-American Occultation Survey (TAOS) aims to detect serendipitous occultations of stars by small (about 1 km diameter) objects in the Kuiper Belt and beyond. Such events are very rare (<0.001 events per star per year) and short in duration (about 200 ms), so many stars must be monitored at a high readout cadence. TAOS monitors typically around 500 stars simultaneously at a 5 Hz readout cadence with four telescopes located at Lulin Observatory in central Taiwan. In this paper, we report the results of the search for small Kuiper Belt Objects (KBOs) in seven years of data. No occultation events were found, resulting in a 95% c.l. upper limit on the slope of the faint end of the KBO size distribution of q = 3.34 to 3.82, depending on the surface density at the break in the size distribution at a diameter of about 90 km., Comment: 11 pages, 9 figures. Submitted to Astronomical Journal 2013 January 16

[Abridged] Context. To construct and interpret the spectral energy distribution (SED) of BL Lacertae objects, simultaneous broad-band observations are mandatory. Aims. We present the results of a dedicated multi-wavelength study of the high-frequency peaked BL Lacertae (HBL) object and known TeV emitter 1ES 2344+514 by means of a pre-organised campaign. Methods. The observations were conducted during simultaneous visibility windows of MAGIC and AGILE in late 2008. The measurements were complemented by Mets\"ahovi, RATAN-600, KVA+Tuorla, Swift and VLBA pointings. Additional coverage was provided by the ongoing long-term F-GAMMA and MOJAVE programs, the OVRO 40-m and CrAO telescopes as well as the Fermi satellite. The obtained SEDs are modelled using a one-zone as well as a self-consistent two-zone synchrotron self-Compton model. Results. 1ES 2344+514 was found at very low flux states in both X-rays and very high energy gamma rays. Variability was detected in the low frequency radio and X-ray bands only, where for the latter a small flare was observed. The X-ray flare was possibly caused by shock acceleration characterised by similar cooling and acceleration time scales. MOJAVE VLBA monitoring reveals a static jet whose components are stable over time scales of eleven years, contrary to previous findings. There appears to be no significant correlation between the 15 GHz and R-band monitoring light curves. The observations presented here constitute the first multi-wavelength campaign on 1ES 2344+514 from radio to VHE energies and one of the few simultaneous SEDs during low activity states. The quasi-simultaneous Fermi-LAT data poses some challenges for SED modelling, but in general the SEDs are described well by both applied models. The resulting parameters are typical for TeV emitting HBLs. Consequently it remains unclear whether a so-called quiescent state was found in this campaign., Comment: 29 pages, 20 figures, 10 tables, accepted for publication by A&A

In December 2010, NASA created a Science Definition Team (SDT) for WFIRST, the Wide Field Infra-Red Survey Telescope, recommended by the Astro 2010 Decadal Survey as the highest priority for a large space mission. The SDT was chartered to work with the WFIRST Project Office at GSFC and the Program Office at JPL to produce a Design Reference Mission (DRM) for WFIRST. Part of the original charge was to produce an interim design reference mission by mid-2011. That document was delivered to NASA and widely circulated within the astronomical community. In late 2011 the Astrophysics Division augmented its original charge, asking for two design reference missions. The first of these, DRM1, was to be a finalized version of the interim DRM, reducing overall mission costs where possible. The second of these, DRM2, was to identify and eliminate capabilities that overlapped with those of NASA's James Webb Space Telescope (henceforth JWST), ESA's Euclid mission, and the NSF's ground-based Large Synoptic Survey Telescope (henceforth LSST), and again to reduce overall mission cost, while staying faithful to NWNH. This report presents both DRM1 and DRM2., Comment: 102 pages, 57 figures, 17 tables

Brown dwarfs are important objects because they may provide a missing link between stars and planets, two populations that have dramatically different formation history. In this paper, we present the candidate binaries with brown dwarf companions that are found by analyzing binary microlensing events discovered during 2004 - 2011 observation seasons. Based on the low mass ratio criterion of q < 0.2, we found 7 candidate events, including OGLE-2004-BLG-035, OGLE-2004-BLG-039, OGLE-2007-BLG-006, OGLE-2007-BLG-399/MOA-2007-BLG-334, MOA-2011-BLG-104/OGLE-2011-BLG-0172, MOA-2011-BLG-149, and MOA-201-BLG-278/OGLE-2011-BLG-012N. Among them, we are able to confirm that the companions of the lenses of MOA-2011-BLG-104/OGLE-2011-BLG-0172 and MOA-2011-BLG-149 are brown dwarfs by determining the mass of the lens based on the simultaneous measurement of the Einstein radius and the lens parallax. The measured mass of the brown dwarf companions are (0.02 +/- 0.01) M_Sun and (0.019 +/- 0.002) M_Sun for MOA-2011-BLG-104/OGLE-2011-BLG-0172 and MOA-2011-BLG-149, respectively, and both companions are orbiting low mass M dwarf host stars. More microlensing brown dwarfs are expected to be detected as the number of lensing events with well covered light curves increases with new generation searches., Comment: 10 pages, 9 figures, 4 tables

We report the extremely high magnification (A > 1000) binary microlensing event OGLE-2007-BLG-514. We obtained good coverage around the double peak structure in the light curve via follow-up observations from different observatories. The binary lens model that includes the effects of parallax (known orbital motion of the Earth) and orbital motion of the lens yields a binary lens mass ratio of q = 0.321 +/- 0.007 and a projected separation of s = 0.072 +/- 0.001$ in units of the Einstein radius. The parallax parameters allow us to determine the lens distance D_L = 3.11 +/- 0.39 kpc and total mass M_L=1.40 +/- 0.18 M_sun; this leads to the primary and secondary components having masses of M_1 = 1.06 +/- 0.13 M_sun and M_2 = 0.34 +/- 0.04 M_sun, respectively. The parallax model indicates that the binary lens system is likely constructed by the main sequence stars. On the other hand, we used a Bayesian analysis to estimate probability distributions by the model that includes the effects of xallarap (possible orbital motion of the source around a companion) and parallax (q = 0.270 +/- 0.005, s = 0.083 +/- 0.001). The primary component of the binary lens is relatively massive with M_1 = 0.9_{-0.3}^{+4.6} M_sun and it is at a distance of D_L = 2.6_{-0.9}^{+3.8} kpc. Given the secure mass ratio measurement, the companion mass is therefore M_2 = 0.2_{-0.1}^{+1.2} M_sun. The xallarap model implies that the primary lens is likely a stellar remnant, such as a white dwarf, a neutron star or a black hole., Comment: 31 pages, 6 figures, 7 tables, accepted in ApJ

The microlensing event OGLE-2008-BLG-510 is characterised by an evident asymmetric shape of the peak, promptly detected by the ARTEMiS system in real time. The skewness of the light curve appears to be compatible both with binary-lens and binary-source models, including the possibility that the lens system consists of an M dwarf orbited by a brown dwarf. The detection of this microlensing anomaly and our analysis demonstrates that: 1) automated real-time detection of weak microlensing anomalies with immediate feedback is feasible, efficient, and sensitive, 2) rather common weak features intrinsically come with ambiguities that are not easily resolved from photometric light curves, 3) a modelling approach that finds all features of parameter space rather than just the `favourite model' is required, and 4) the data quality is most crucial, where systematics can be confused with real features, in particular small higher-order effects such as orbital motion signatures. It moreover becomes apparent that events with weak signatures are a silver mine for statistical studies, although not easy to exploit. Clues about the apparent paucity of both brown-dwarf companions and binary-source microlensing events might hide here., Comment: 17 pages with 8 figures, MNRAS submitted

Most known extrasolar planets (exoplanets) have been discovered using the radial velocity$^{\bf 1,2}$ or transit$^{\bf 3}$ methods. Both are biased towards planets that are relatively close to their parent stars, and studies find that around 17--30% (refs 4, 5) of solar-like stars host a planet. Gravitational microlensing$^{\bf 6\rm{\bf -}\bf 9}$, on the other hand, probes planets that are further away from their stars. Recently, a population of planets that are unbound or very far from their stars was discovered by microlensing$^{\bf 10}$. These planets are at least as numerous as the stars in the Milky Way$^{\bf 10}$. Here we report a statistical analysis of microlensing data (gathered in 2002--07) that reveals the fraction of bound planets 0.5--10 AU (Sun--Earth distance) from their stars. We find that 17$_{\bf -9}^{\bf +6}$% of stars host Jupiter-mass planets (0.3--10 $\MJ$, where $\MJ {\bf = 318}$ $\Mearth$ and $\Mearth$ is Earth's mass). Cool Neptunes (10--30 $\Mearth$) and super-Earths (5--10 $\Mearth$) are even more common: their respective abundances per star are 52$_{\bf -29}^{\bf +22}$% and 62$_{\bf -37}^{\bf +35}$%. We conclude that stars are orbited by planets as a rule, rather than the exception., Comment: Letter, 2 figures

Microlensing can provide a useful tool to probe binary distributions down to low-mass limits of binary companions. In this paper, we analyze the light curves of 8 binary lensing events detected through the channel of high-magnification events during the seasons from 2007 to 2010. The perturbations, which are confined near the peak of the light curves, can be easily distinguished from the central perturbations caused by planets. However, the degeneracy between close and wide binary solutions cannot be resolved with a $3\sigma$ confidence level for 3 events, implying that the degeneracy would be an important obstacle in studying binary distributions. The dependence of the degeneracy on the lensing parameters is consistent with a theoretic prediction that the degeneracy becomes severe as the binary separation and the mass ratio deviate from the values of resonant caustics. The measured mass ratio of the event OGLE-2008-BLG-510/MOA-2008-BLG-369 is $q\sim 0.1$, making the companion of the lens a strong brown-dwarf candidate., Comment: 10 figures, 6 tables, 26 pages