Search Publications
Faint Stars in a Faint Galaxy. I. Ultradeep Photometry of the Boötes I Ultrafaint Dwarf Galaxy
Wyse, Rosemary F. G.; Kozhurina-Platais, Vera; Platais, Imants +2 more
We present an analysis of new, extremely deep images of the resolved stellar population of the Boötes I ultrafaint dwarf spheroidal galaxy. These new data were taken with the Hubble Space Telescope, using the Advanced Camera for Surveys (Wide Field Camera) and Wide Field Camera 3 (UVIS), with filters F606W and F814W (essentially V and I), as part …
X-ray properties of the X-CLASS-redMaPPer galaxy cluster sample: the luminosity-temperature relation
Raychaudhury, Somak; Clerc, Nicolas; Lieu, Maggie +7 more
This article presents the results of a spectroscopic analysis of the X-CLASS-redMaPPer (XC1-RM) galaxy cluster sample. X-CLASS is a serendipitous search for clusters in X-ray wavebands based on the XMM-Newton archive, whereas redMaPPer is an optical cluster catalogue derived from the Sloan Digital Sky Survey (SDSS). The present sample comprises 92…
Comparison of Multi-class and Binary Classification Machine Learning Models in Identifying Strong Gravitational Lenses
Bottrell, Connor; Fabbro, Sebastien; Teimoorinia, Hossen +1 more
Typically, binary classification lens-finding schemes are used to discriminate between lens candidates and non-lenses. However, these models often suffer from substantial false-positive classifications. Such false positives frequently occur due to images containing objects such as crowded sources, galaxies with arms, and also images with a central…
Multi-wavelength observations of the BL Lac object Fermi J1544-0649: One year after its awakening
Kong, A. K. H.; Tam, P. H. T.; Mao, J. +15 more
We report observations of a transient source Fermi J1544-0649 from radio to γ-rays. Fermi J1544-0649 was discovered by the Fermi-LAT in May 2017. Follow-up Swift-XRT observations revealed three flaring episodes through March 2018, and the peak X-ray flux is about 103 higher than the ROSAT all-sky survey (RASS) flux upper limit. Optical …
Occultation observations of Saturn's rings with Cassini VIMS
Nicholson, Philip D.; Hedman, Matthew M.; Sotin, Christophe +9 more
We describe the prediction, design, execution and calibration of stellar and solar occultation observations of Saturn's rings by the Visual and Infrared Mapping Spectrometer (VIMS) instrument on the Cassini spacecraft. Particular attention is paid to the technique developed for onboard acquisition of the stellar target and to the geometric and pho…
Modified Newtonian Gravity, Wide Binaries and the Tully-Fisher Relation
Acedo, Luis
A recent study of a sample of wide binary star systems from the Hipparcos and Gaia catalogues has found clear evidence of a gravitational anomaly of the same kind as that appearing in galaxies and galactic clusters. Instead of a relative orbital velocity decaying as the square root of the separation, ΔV∝r‑1/2, it was shown that an asymptotic const…
Dissecting the Global Cold Dust Properties and Possible Submillimeter Excess of 13 Nearby Spiral Galaxies from the NGLS
Wilson, Christine D.; Li, Dalei; Tang, Xindi +9 more
We select 13 nearby spiral galaxies from the Nearby Galaxies Legacy Survey (NGLS) project and perform spectral energy distribution fitting for each galaxy applying two-component modified blackbody models on a global scale aim to probe the potential submillimeter (submm) excess. We find that NGC 2976, NGC 3351, and NGC 4631 show excess emission at …
Lithological mapping of Eratosthenes crater region using Moon Mineralogy Mapper of Chandrayaan-1
Kumaresan, P. R.; Saravanavel, J.; Palanivel, K.
Selenological exploration (lunar geology) involves mapping and delineation of different rock types and minerals present in the Moon. Various lunar missions with multi-spectral sensors provided preliminary information about the lithological and mineralogical occurrences on the Moon. The Chandrayaan-1 Moon Mineralogy Mapper (M3), provided…
Magnetic Rayleigh-Taylor Instability in an Experiment Simulating a Solar Loop
Zhang, Yang; Wongwaitayakornkul, Pakorn; Bellan, Paul M.
A hoop force driven magnetic Rayleigh-Taylor instability (MRTI) is observed in a laboratory experiment that simulates a solar coronal loop. Increase of the axial wavelength λ is observed when the axial magnetic field increases. This scaling is consistent with the theoretical MRTI growth rate ${\gamma }^{2}={gk}-2{\left({\boldsymbol{k}}\cdot {{\bol…
A Simple Unified Spectroscopic Indicator of Stellar Luminosity: The Extended Flux-weighted Gravity-Luminosity Relationship
Rix, Hans-Walter; Kudritzki, Rolf-Peter; Urbaneja, Miguel A.
We show that for a wide range of stellar masses, from 0.3 to 20 M⊙, and for evolutionary phases from the main sequence to the beginning of the red giant stage, the stellar flux-weighted gravity, gF ≅ g/ ${T}_{\mathrm{eff}}^{4}$ , is tightly correlated with absolute bolometric magnitude ${M}_{\mathrm{bol}}$ . Such a correlatio…