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Compact galaxies and the size-mass galaxy distribution from a colour-selected sample at 0.04 < z < 0.15 supplemented by ugrizYJHK photometric redshifts
Baldry, Ivan K.; Sullivan, Tricia; Rani, Raffaele +1 more
The size-mass galaxy distribution is a key diagnostic for galaxy evolution. Massive compact galaxies are potential surviving relics of a high-redshift phase of star formation. Some of these could be nearly unresolved in Sloan Digital Sky Survey (SDSS) imaging and thus not included in galaxy samples. To overcome this, a sample was selected from the…
Connecting Galactic Outflows and Star Formation: Inferences from Hα Maps and Absorption-line Spectroscopy at 1 ≲ z ≲ 1.5
Martin, Crystal L.; Erb, Dawn K.; Prusinski, Nikolaus Z.
We investigate the connection between galactic outflows and star formation using two independent data sets covering a sample of 22 galaxies between 1 ≲ z ≲ 1.5. The Hubble Space Telescope WFC3/G141 grism provides low spectral resolution, high spatial resolution spectroscopy yielding Hα emission-line maps from which we measure the spatial extent an…
The RS CVn-type Star GT Mus Shows Most Energetic X-Ray Flares Throughout the 2010s
Hamaguchi, Kenji; Corcoran, Michael F.; Maeda, Yoshitomo +14 more
We report that the RS CVn-type star GT Mus (HR 4492, HD 101379+HD 101380) was the most active star in the X-ray sky in the last decade in terms of the scale of recurrent energetic flares. We detected 11 flares from GT Mus in 8 yr of observations with the Monitor of All-sky X-ray Image (MAXI) from 2009 August to 2017 August. The detected flare peak…
Galactic open cluster Cepheids - a census based on Gaia EDR3
Chen, Xiaodian; Zhou, Xiaoyue
In the Gaia era, the membership analysis and parameter determination of open clusters (OCs) are more accurate. We performed a census of OC's classical Cepheids based on Gaia Early Data Release 3 (EDR3) and obtained a sample of 33 OC Cepheids fulfilling the constraints of the spatial position, proper motion, parallax, and evolution state. 13 of 33 …
Properties of High-Frequency Type II Radio Bursts and Their Relation to the Associated Coronal Mass Ejections
Gopalswamy, N.; Yashiro, S.; Mäkelä, P. +3 more
Solar radio bursts are often early indicators of space weather events such as coronal mass ejections (CMEs). In this study, we determined the properties of a sample of 40 high-starting-frequency (≥ 150 MHz) type II radio bursts and the characteristics of the associated CMEs such as width, location and speed during 2010-2016. The high starting freq…
The Galactic neutron star population - I. An extragalactic view of the Milky Way and the implications for fast radio bursts
Lyman, J. D.; Groot, P. J.; Nelemans, G. +2 more
A key tool astronomers have to investigate the nature of extragalactic transients is their position on their host galaxies. Galactocentric offsets, enclosed fluxes, and the fraction of light statistic are widely used at different wavelengths to help infer the nature of transient progenitors. Motivated by the proposed link between magnetars and fas…
Unsupervised Machine Learning for the Identification of Preflare Spectroscopic Signatures
De Pontieu, Bart; Sainz Dalda, Alberto; Woods, Magnus M.
The study of the preflare environment is of great importance to understanding what drives solar flares. k-means clustering, an unsupervised machine-learning technique, has the ability to cluster large data set in a way that would be impractical or impossible for a human to do. In this paper we present a study using k-means clustering to identify p…
NGC 1261: An r-process enhanced globular cluster from the Gaia-Enceladus event
McWilliam, Andrew; Koch-Hansen, Andreas J.; Hansen, Camilla J.
Our Milky Way (MW) has witnessed a series of major accretion events in the past. One of the later additions, the Gaia-Enceladus merger, has contributed a considerable mass to the inner Galaxy, but also generously donated to the outer halo. So far, associations with present-day MW globular clusters (GCs) have been chiefly based on their kinematics …
DH Type II Radio Bursts During Solar Cycles 23 and 24: Frequency-Dependent Classification and Their Flare-CME Associations
Joshi, Bhuwan; Cho, Kyung-Suk; Patel, Binal D. +1 more
We present the characteristics of DH type II bursts for the Solar Cycles 23 and 24. The bursts are classified according to their end frequencies into three categories: Low-Frequency Group (LFG; 20 kHz ≤ f ≤ 200 kHz), Medium-Frequency Group (MFG; 200 kHz <f ≤1 MHz), and High-Frequency Group (HFG; 1 MHz <f ≤16 MHz). We find that the sources fo…
A first glimpse at the Galactic plane with the ASKAP: the SCORPIO field
Umana, G.; Michałowski, M. J.; Kothes, R. +25 more
In the broad context of the Australian Square Kilometer Array Pathfinder (ASKAP) early-science phase and preparation for the related surveys, we report the first radio observations towards the Galactic plane. The targeted field was chosen to encompass the entire SCORPIO survey, one of the several pathfinder projects for the Evolutionary Map of the…