Simulation Software: Then, Now and Virtual Observatory

Like hardware, evolution of software has had a major impact on the field of particle simulations. This paper illustrates how simulation software has evolved, and where it can go. In addition, with the various ongoing Virtual Observatory efforts, producers of theory data should think more about sharing their data! Some examples are given of what we can do with our data and how to share it with our colleagues and observers. In the Appendix we summarize the findings of an informal data and software usage survey that we took during this conference.Comment: 10 pages, 1 figure, to appear in "Astrophysical Supercomputing Using Particle Simulations", eds. P. Hut and J. Makino, IAU Symposium 208, Tokyo, July 200

Velocity Fields of Disk Galaxies

Two dimensional velocity fields have been an important tool for nearly 30 years and are instrumental in understanding galactic mass distributions and deviations from an ideal galactic disk. Recently a number of new instruments have started to produce more detailed velocity fields of the disks and nuclear regions of galaxies. This paper summarizes some of the underlying techniques for constructing velocity fields and deriving rotation curves. It also urges to simulate observations from the data-cube stage to reject subtle biases in derived quantities such as rotation curves.Comment: 12 pages, 6 figures, to be published in Disks of Galaxies: Kinematics, Dynamics and Interactions, E. Athanassoula and A. Bosma (Eds.), ASP Conf. Series, in press (2002

MIS: a MIRIAD Interferometry Singledish toolkit

Building on the "drPACS" contribution at ADASS XX of a simple Unix pipeline infrastructure, we implemented a pipeline toolkit using the package MIRIAD to combine Interferometric and Single Dish data (MIS). This was prompted by our observations made with the Combined Array For Research in Millimeter-wave Astronomy (CARMA) interferometer of the star-forming region NGC 1333, a large survey highlighting the new 23-element and singledish observing modes. The project consists of 20 CARMA datasets each containing interferometric as well as simultaneously obtained single dish data, for 3 molecular spectral lines and continuum, in 527 different pointings, covering an area of about 8 by 11 arcminutes. A small group of collaborators then shared this toolkit and their parameters via CVS, and scripts were developed to ensure uniform data reduction across the group. The pipeline was run end-to-end each night as new observations were obtained, producing maps that contained all the data to date. We will show examples of the scripts and data products. This approach could serve as a model for repeated calibration and mapping of large mixed-mode correlation datasets from ALMA

Availability of Hyperlinked Resources in Astrophysics Papers

Astrophysics papers often rely on software which may or may not be available, and URLs are often used as proxy citations for software and data. We extracted all URLs from two journals' 2015 research articles, removed those from certain long-term reliable domains, and tested the remainder to determine what percentage of these URLs were accessible in October 2018.Comment: 4 pages, 2 tables; revise

Knowledge Discovery Framework for the Virtual Observatory

We describe a framework that allows a scientist-user to easily query for information across all Virtual Observatory (VO) repositories and pull it back for analysis. This framework hides the gory details of meta-data remediation and data formatting from the user, allowing them to get on with search, retrieval and analysis of VO data as if they were drawn from a single source using a science based terminology rather than a data-centric one.Comment: ADASS XVI ASP Conference Series, Vol. 376, proceedings of the conference held 15-18 October 2006 in Tucson, Arizona, USA. Edited by Richard A. Shaw, Frank Hill and David J. Bell., p.56

Practices in Code Discoverability

Much of scientific progress now hinges on the reliability, falsifiability and reproducibility of computer source codes. Astrophysics in particular is a discipline that today leads other sciences in making useful scientific components freely available online, including data, abstracts, preprints, and fully published papers, yet even today many astrophysics source codes remain hidden from public view. We review the importance and history of source codes in astrophysics and previous efforts to develop ways in which information about astrophysics codes can be shared. We also discuss why some scientist coders resist sharing or publishing their codes, the reasons for and importance of overcoming this resistance, and alert the community to a reworking of one of the first attempts for sharing codes, the Astrophysics Source Code Library (ASCL). We discuss the implementation of the ASCL in an accompanying poster paper. We suggest that code could be given a similar level of referencing as data gets in repositories such as ADS.Comment: ASCL codes are now incoorporated into AD

High Velocity Clouds: the Missing Link

Hierarchical structure formation models predict the existence of large numbers of low velocity dispersion dark halos. Galaxy surveys find far fewer galaxies than predicted by analytical estimates and numerical simulations. In this paper, we suggest that these dark halos are not missing, but have been merely misplaced in the galactic astronomy section of the journals: they are the High Velocity Clouds (HVCs). We review the predictions of our model for the Local Group origin of the HVCs and its implications for the formation and the evolution of our Galaxy. We describe recent observations that confirm many of earlier predictions and discuss future tests of the model.Comment: 17 pages, 6 figures To appear in High Velocity Clouds (Kluwer: Dordrecht), Edited by Ulrich Schwarz and Hugo van Woerden Uses crckapb.st

Galaxy Cluster Bulk Flows and Collision Velocities in QUMOND

We examine the formation of clusters of galaxies in numerical simulations of a QUMOND cosmogony with massive sterile neutrinos. Clusters formed in these exploratory simulations develop higher velocities than those found in {\Lambda}CDM simulations. The bulk motions of clusters attain about 1000 km/s by low redshift, comparable to observations whereas {\Lambda}CDM simulated clusters tend to fall short. Similarly, high pairwise velocities are common in cluster-cluster collisions like the Bullet cluster. There is also a propensity for the most massive clusters to be larger in QUMOND and to appear earlier than in {\Lambda}CDM, potentially providing an explanation for 'pink elephants' like El Gordo. However, it is not obvious that the cluster mass function can be recovered.Comment: 11 pages, 8 figures, accepted for publication in Ap

Software metadata: How much is enough?

Broad efforts are underway to capture metadata about research software and retain it across services; notable in this regard is the CodeMeta project. What metadata are important to have about (research) software? What metadata are useful for searching for codes? What would you like to learn about astronomy software? This BoF sought to gather information on metadata most desired by researchers and users of astro software and others interested in registering, indexing, capturing, and doing research on this software. Information from this BoF could conceivably result in changes to the Astrophysics Source Code Library (ASCL) or other resources for the benefit of the community or provide input into other projects concerned with software metadata.Comment: 4 pages; to be published in ADASS XXVII (held Oct 22-26, 2017 in Santiago, Chile) proceeding

High Velocity Clouds: Building Blocks of the Local Group

We suggest that the high--velocity clouds (HVCs) are large clouds, with typical diameters of 25 kpc and containing 5e7 solar masses of neutral gas and 3e8 solar masses of dark matter, falling onto the Local Group; altogether the HVCs contain 10$^{11}$ solar masses of neutral gas. Our reexamination of the Local-Group hypothesis for the HVCs connects their properties to the hierarchical structure formation scenario and to the gas seen in absorbtion towards quasars. We begin by showing that at least one HVC complex (besides the Magellanic Stream) must be extragalactic at a distance > 40 kpc from the Galactic center, with a diameter > 20 kpc and a mass > 1e8 solar masses. We interpret the more distant HVCs as dark matter ``mini--halos'' moving along filaments towards the Local Group. Most poor galaxy groups should contain HI structures to large distances bound to the group. The HVCs are local analogues of the Lyman--limit clouds We argue that there is a Galactic fountain in the Milky Way, but that the fountain does not explain the origin of the HVCs. Our analysis of the HI data leads to the detection of a vertical infall of low-velocity gas towards the plane. This implies that the chemical evolution of the Galactic disk is governed by episodic infall of metal-poor HVC gas that only slowly mixes with the rest of the interstellar medium. The Local--Group infall hypothesis makes a number of testable predictions. The HVCs should have sub-solar metallicities. Their H$\alpha$ emission should be less than that seen from the Magellanic Stream. The clouds should not be seen in absorption to nearby stars. The clouds should be detectable in both emission and absorption around other groups.Comment: 65 pages, 27 figures (26 postscript, 1 gif). Submitted to Astrophysical Journal Full figures and paper available at http://www.astro.princeton.edu/~dns