Starburst99 is a comprehensive set of model predictions for spectrophotometric and related properties of galaxies with active star formation. The models are an improved and extended version of the data set previously published by Leitherer & Heckman. We have upgraded our code by implementing the latest set of stellar evolution models of the Geneva group and the model atmosphere grid compiled by Lejeune et al. Several predictions which were not included in the previous publication are shown here for the first time. The models are presented in a homogeneous way for five metallicities between Z = 0.040 and 0.001 and three choices of the initial mass function. The age coverage is 106—109 yr. We also show the spectral energy distributions which are used to compute colors and other quantities. The full data set is available for retrieval at a Web site, which allows users to run specific models with nonstandard parameters as well. We also make the source code available to the community.

https://iopscience.iop.org/article/10.1086/313233/pdf

Starburst99: Synthesis Models for Galaxies with Active Star Formation

On 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of $\sim 1.7\,{\rm{s}}$ with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg2 at a luminosity distance of ${40}_{-8}^{+8}$ Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 $\,{M}_{\odot }$. An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at $\sim 40\,{\rm{Mpc}}$) less than 11 hours after the merger by the One-Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over ~10 days. Following early non-detections, X-ray and radio emission were discovered at the transient's position $\sim 9$ and $\sim 16$ days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in NGC 4993 followed by a short gamma-ray burst (GRB 170817A) and a kilonova/macronova powered by the radioactive decay of r-process nuclei synthesized in the ejecta.

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Multi-messenger observations of a binary neutron star merger

We review progress over the past decade in observations of large-scale star formation, with a focus on the interface between extragalactic and Galactic studies. Methods of measuring gas contents and star-formation rates are discussed, and updated prescriptions for calculating star-formation rates are provided. We review relations between star formation and gas on scales ranging from entire galaxies to individual molecular clouds.

Star Formation in the Milky Way and Nearby Galaxies

▪ Abstract The Local Group dwarf galaxies offer a unique window to the detailed properties of the most common type of galaxy in the Universe. In this review, I update the census of Local Group dwarfs based on the most recent distance and radial velocity determinations. I then discuss the detailed properties of this sample, including (a) the integrated photometric parameters and optical structures of these galaxies, (b) the content, nature, and distribution of their interstellar medium (ISM), (c) their heavy-element abundances derived from both stars and nebulae, (d) the complex and varied star-formation histories of these dwarfs, (e) their internal kinematics, stressing the relevance of these galaxies to the “dark matter problem” and to alternative interpretations, and (f) evidence for past, ongoing, and future interactions of these dwarfs with other galaxies in the Local Group and beyond. To complement the discussion and to serve as a foundation for future work, I present an extensive set of basic observ...

/pdf/dwarf-galaxies-of-the-local-group-4ham6n81f0.pdf

Dwarf galaxies of the local group

Monthly Notices is one of the three largest general primary astronomical research publications. It is an international journal, published by the Royal Astronomical Society. This article 1 describes its publication policy and practice.

Monthly Notices of the Royal Astronomical Society

Non-thermal radio emission from Wolf-Rayet stars


 We use data from the pilot observations of the EMU/POSSUM surveys to study the ‘missing supernova remnant (SNR) problem’, the discrepancy between the number of Galactic SNRs that have been observed, and the number that are estimated to exist. The Evolutionary Map of the Universe (EMU) and the Polarization Sky Survey of the Universe’s Magnetism (POSSUM) are radio sky surveys that are conducted using the Australian Square Kilometre Array Pathfinder (ASKAP). We report on the properties of seven known SNRs in the joint Galactic pilot field, with an approximate longitude and latitude of 323° ≤ l ≤ 330° and −4° ≤ b ≤ 2°, respectively, and identify 21 SNR candidates. Of these, four have been previously identified as SNR candidates, three were previously listed as a single SNR, 13 have not been previously studied, and one has been studied in the infrared. These are the first discoveries of Galactic SNR candidates with EMU/POSSUM and, if confirmed, they will increase the SNR density in this field by a factor of 4. By comparing our SNR candidates to the known Galactic SNR population, we demonstrate that many of these sources were likely missed in previous surveys due to their small angular size and/or low surface brightness. We suspect that there are SNRs in this field that remain undetected due to limitations set by the local background and confusion with other radio sources. The results of this paper demonstrate the potential of the full EMU/POSSUM surveys to uncover more of the missing Galactic SNR population.

A catalogue of radio supernova remnants and candidate supernova remnants in the EMU/POSSUM Galactic pilot field

We present follow-up high-resolution H I, deep optical, and molecular observations of the intergalactic gas cloud HIPASS J0731-69, and re-examine the question of its origin in light of these new data. 1. Background An intergalactic gas cloud was discovered serendipitously during the course of the H I Parkes All-Sky Survey (Barnes et al. 2001), lying at a projected distance of 180 kpc from the asymmetric spiral galaxy NGC 2442 (Ryder et al. 2001). This object, designated HIPASS J0731-69, contains rv109 M8 of H I, or nearly 1/3 as much atomic gas as NGC 2442 itself. No obvious optical counterpart could be found in the Digitised Sky Survey (DSS). 2. Follow-up Observations and Conclusions HIPASS J0731-69 was observed for 4 x 12 hr with the Australia Telescope Compact Array! (ATCA) in its compact 375 m configuration in February 2001. At 2' resolution, HIPASS J0731-69 is observed to break up into seven or so distinct, or loosely-connected clumps (Figure 1), each containing rv 5 X 107 M8 of HI. The peak H I surface density in any clump is < 0.3 M8 pc-2, well below the apparent "threshold" for star formation (Martin & Kennicutt 2001). The area surrounding HIPASS J0731-69 was observed for 3000 s in the Bband, using the Wide Field Imager (WFI) 8Kx8K CCD mosaic at the prime focus of the Anglo-Australian Telescope, in January 2003. Although this data reaches much fainter levels (B rv 24) than the DSS, Fig. 1 still shows no clear optical counterparts to three of the densest H I clumps. Each of the H I clumps identified with the ATCA was observed for up to 6 hr with the Swedish-ESO Submillimetre Telescope (SEST) in February 2002, IThe Australia Telescope is funded by the Commonwealth of Australia for operation as a National Facility managed by CSIRO. 44 available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/S0074180900197098 Downloaded from https://www.cambridge.org/core. IP address: 54.70.40.11, on 02 Mar 2019 at 04:06:27, subject to the Cambridge Core terms of use,

/pdf/hipass-j0731-69-tidal-debris-or-primordial-gas-cloud-4bp6fkpo83.pdf

HIPASS J0731-69: Tidal Debris, or Primordial Gas Cloud?

Observational astronomers survey the sky in great detail to gain a better understanding of many types of astronomical phenomena In particular, the formation and evolution of galaxies, including our own, is a wide field of research in astronomy Three dimensional (spatial) scientific visualisation is typically limited to simulated galaxies, due to the inherently two dimensional spatial resolution of Earth-based observations We present a novel approach to reconstruct and visualise 3D representations of galaxies based on observational data, using the scientific visualisation software Splotch to generate high quality visual representations that provide a new perspective of galaxies nearby the Milky Way

Bärbel S. Koribalski

Papers

Non-thermal radio emission from Wolf-Rayet stars

A catalogue of radio supernova remnants and candidate supernova remnants in the EMU/POSSUM Galactic pilot field

HIPASS J0731-69: Tidal Debris, or Primordial Gas Cloud?

3D Modelling and Visualisation of Observed Galaxies

A new view of observed galaxies through 3D modelling and visualisation