Asteroids Observed by The Sloan Digital Sky Survey

We announce the first public release of the SDSS Moving Object Catalog, with SDSS observations for 58,117 asteroids. The catalog lists astrometric and photometric data for moving objects observed prior to Dec 15, 2001, and also includes orbital elements for 10,592 previously known objects. We analyze the correlation between the orbital parameters and optical colors for the known objects, and confirm that asteroid dynamical families, defined as clusters in orbital parameter space, also strongly segregate in color space. Their distinctive optical colors indicate that the variations in chemical composition within a family are much smaller than the compositional differences between families, and strongly support earlier suggestions that asteroids belonging to a particular family have a common origin.Comment: 6 pages, 1 color figure, to be presented at "Astronomical Telescopes & Instrumentation", SPIE 200

Coping with COVID-19: The sociomaterial dimensions of living with pre-existing mental illness during the early stages of the coronavirus crisis

In this article, we use the case study method to detail the experiences of five participants who reported living with pre-existing mental illness during COVID-19. We adopted a sociomaterial analytical approach, seeking to identify how human and nonhuman agents came together to generate states of wellbeing or distress during this challenging period. As the case studies show, feelings of anxiety, fear and risk were generated from the following sociomaterial conditions: loss of face-to-face contact with friends and family members; concerns about hygiene and infecting others; financial stress; loss of regular paid employment or volunteering work; public spaces; and the behaviour of unknown others in public spaces. The agents and practices that emerged as most important for opening capacities for coping and maintaining wellness during lockdown included: the space of the home; contact with a small number of intimate others; online therapeutic care; practising self-care skills learnt from previous difficult times; helping and supporting others; engaging in leisure activities; and the companionship of pets. Contributing to an affirmative approach to more-than-human assemblages of health, distress and recovery, these findings demonstrate what bodies can do in times of crisis and the agents and practices that can generate capacities for coping

Learning about COVID-19: a qualitative interview study of Australians’ use of information sources

Background: A multitude of information sources are available to publics when novel infectious diseases first emerge. In this paper, we adopt a qualitative approach to investigate how Australians learnt about the novel coronavirus and COVID-19 and what sources of information they had found most useful and valuable during the early months of the pandemic. Methods: In-depth semi-structured telephone interviews were conducted with a diverse group of 40 Australian adults in mid-2020 about their experiences of the COVID-19 crisis. Participants were recruited through Facebook advertising. Detailed case studies were created for each participant, providing the basis of a thematic analysis which focused on the participants’ responses to the questions about COVID-19-related information sources. Results: Diverse sources of COVID-19-related information, including traditional media, online media and in-person interactions, were actively accessed, appraised and engaged with by participants. There was a high level of interest in COVID-19 information as people grappled with uncertainty, anxiety and feeling overwhelmed. Certain key events or experiences made people become aware that the outbreak was threatening Australia and potentially themselves. Most people demonstrated keen awareness that misinformation was rife in news outlets and social media sites and that they were taking steps to determine the accuracy of information. High trust was placed in health experts, scientists and government sources to provide reliable information. Also important to participants were informal discussions with friends and family members who were experts or working in relevant fields, as well as engaging in-person in interactions and hearing from friends and family who lived overseas about what COVID-19 conditions were like there. Conclusion: A constantly changing news environment raises challenges for effective communication of risk and containment advice. People can become confused, distressed and overwhelmed by the plethora of information sources and fast-changing news environment. On the other hand, seeking out information can provide reassurance and comfort in response to anxiety and uncertainty. Clarity and consistency in risk messaging is important, as is responding quickly to changes in information and misinformation. Further research should seek to identify any changes in use of and trust in information sources as time goes by

A Modified Magnitude System that Produces Well-Behaved Magnitudes, Colors, and Errors Even for Low Signal-to-Noise Ratio Measurements

We describe a modification of the usual definition of astronomical magnitudes, replacing the usual logarithm with an inverse hyperbolic sine function; we call these modified magnitudes `asinh magnitudes'. For objects detected at signal-to-noise ratios of greater than about five, our modified definition is essentially identical to the traditional one; for fainter objects (including those with a formally negative flux) our definition is well behaved, tending to a definite value with finite errors as the flux goes to zero. This new definition is especially useful when considering the colors of faint objects, as the difference of two `asinh' magnitudes measures the usual flux ratio for bright objects, while avoiding the problems caused by dividing two very uncertain values for faint objects. The Sloan Digital Sky Survey (SDSS) data products will use this scheme to express all magnitudes in their catalogs.Comment: 11 pages, including 3 postscript figures. Submitted to A

Wavelength Dependent PSFs and their impact on Weak Lensing Measurements

We measure and model the wavelength dependence of the PSF in the Hyper Suprime-Cam (HSC) Subaru Strategic Program (SSP) survey. We find that PSF chromaticity is present in that redder stars appear smaller than bluer stars in the $g, r,$ and $i$-bands at the 1-2 per cent level and in the $z$ and $y$-bands at the 0.1-0.2 per cent level. From the color dependence of the PSF, we fit a model between the monochromatic PSF trace radius, $R$, and wavelength of the form $R(\lambda)\propto \lambda^{b}$. We find values of $b$ between -0.2 and -0.5, depending on the epoch and filter. This is consistent with the expectations of a turbulent atmosphere with an outer scale length of $\sim 10-100$ m, indicating that the atmosphere is dominating the chromaticity. We find evidence in the best seeing data that the optical system and detector also contribute some wavelength dependence. Meyers and Burchat (2015) showed that $b$ must be measured to an accuracy of $\sim 0.02$ not to dominate the systematic error budget of the Large Synoptic Survey Telescope (LSST) weak lensing (WL) survey. Using simple image simulations, we find that $b$ can be inferred with this accuracy in the $r$ and $i$-bands for all positions in the LSST field of view, assuming a stellar density of 1 star arcmin$^{-2}$ and that the optical PSF can be accurately modeled. Therefore, it is possible to correct for most, if not all, of the bias that the wavelength-dependent PSF will introduce into an LSST-like WL survey.Comment: 14 pages, 10 figures. Submitted to MNRAS. Comments welcom

Towards a fully consistent Milky Way disc model - II. The local disc model and SDSS data of the NGP region

We have used the self-consistent vertical disc models of the solar neighbourhood presented in Just & Jahreiss (2010), which are based on different star formation histories (SFR) and fit the local kinematics of main sequence stars equally well, to predict star counts towards the North Galactic Pole (NGP). We combined these four different models with the local main sequence in the filter system of the SDSS and predicted the star counts in the NGP field with b>80deg. All models fit the Hess diagrams in the F-K dwarf regime better than 20 percent and the star number densities in the solar neighbourhood are consistent with the observed values. The chi^2 analysis shows that model A is clearly preferred with systematic deviations of a few percent only. The SFR of model A is characterised by a maximum at an age of 10Gyr and a decline by a factor of four to the present day value of 1.4Msun/pc^2/Gyr. The thick disc can be modelled very well by an old isothermal simple stellar population. The density profile can be approximated by a sech^(alpha_t) function. We found a power law index alpha_t=1.16 and a scale height of 800pc corresponding to a vertical velocity dispersion of 45.3km/s. About 6 percent of the stars in the solar neighbourhood are thick disc stars.Comment: 11 pages, 12 figures, accepted by MNRAS. The qualtity of figures 10 and 12 are much better in the .ps version than the .pdf versio