Apertif is a phased-array feed system for the Westerbork Synthesis
Radio Telescope (WSRT), operating at 1.4 GHz and providing forty
instantaneous beams over 300 MHz of bandwidth. This data release
includes the image of the Lockman Hole field observed with Apertif.
The image covers 136 square degree region, has an angular resolution
of 15x13 arcseconds and a median background noise of 27 μJy/beam. The
corresponding source catalog, complete down to the 0.3 mJy level,
includes 55166 sources.
https://science.astron.nl/telescopes/wsrt-apertif/apertif-data-access/data-releases/apertif-single-fields/
Apertif Time Domain FRB detection cone search (DR2)
Short Name:
Detected FRB
Date:
31 Jul 2024 11:50:27
Publisher:
ASTRON
Description:
This is the final, full data release from the Apertif Radio Transient
System (ARTS), a supercomputing radio-telescope instrument that
performed real-time FRB detection and localisation on the Westerbork
Synthesis Radio Telescope (WSRT) interferometer. It reached
coherent-addition sensitivity over the entire field of the view of the
primary- dish beam. The Apertif FRB survey (ALERT) detected 24 new
FRBs, and interferometrically localised each of these to 0.4−10 sq.
arcmin. All detections are broad band and very narrow, of order 1 ms
duration, with high dispersion measures. Please note that the ARTS DR2
collection includes all data from the DR1 collection.
Apertif Time Domain FRB detection cone search (DR1)
Short Name:
Detected FRB
Date:
31 Jul 2024 11:50:09
Publisher:
ASTRON
Description:
This is the first release of data from the Apertif Radio Transient
System (ARTS), a supercomputing radio-telescope instrument that
performs real-time FRB detection and localisation on the Westerbork
Synthesis Radio Telescope (WSRT) interferometer. It reaches
coherent-addition sensitivity over the entire field of the view of the
primary- dish beam. After commissioning results verified the system
performed as planned, we initiated the Apertif FRB survey (ALERT).
Over the first 5 weeks we observed at design sensitivity in 2019, we
detected 5 new FRBs, and interferometrically localised each of these
to 0.4−10 sq. arcmin. All detections are broad band and very narrow,
of order 1 ms duration, and unscattered. Dispersion measures are
generally high. Please note that the ARTS DR1 collection available
from this end-point is superseded by the ARTS DR2 collection. DR2
includes all data from the DR1 collection that can be queried here.
The ARTS DR2 FRB detection cone search can be reached at
https://vo.astron.nl/arts_dr2/q/det_cone/form.
Apertif Time Domain FRB observation cone search (DR2)
Short Name:
Observed FRBs
Date:
31 Jul 2024 11:50:27
Publisher:
ASTRON
Description:
This is the final, full data release from the Apertif Radio Transient
System (ARTS), a supercomputing radio-telescope instrument that
performed real-time FRB detection and localisation on the Westerbork
Synthesis Radio Telescope (WSRT) interferometer. It reached
coherent-addition sensitivity over the entire field of the view of the
primary- dish beam. The Apertif FRB survey (ALERT) detected 24 new
FRBs, and interferometrically localised each of these to 0.4−10 sq.
arcmin. All detections are broad band and very narrow, of order 1 ms
duration, with high dispersion measures. Please note that the ARTS DR2
collection includes all data from the DR1 collection.
Apertif Time Domain FRB observation cone search (DR1)
Short Name:
Observed FRBs
Date:
31 Jul 2024 11:50:09
Publisher:
ASTRON
Description:
This is the first release of data from the Apertif Radio Transient
System (ARTS), a supercomputing radio-telescope instrument that
performs real-time FRB detection and localisation on the Westerbork
Synthesis Radio Telescope (WSRT) interferometer. It reaches
coherent-addition sensitivity over the entire field of the view of the
primary- dish beam. After commissioning results verified the system
performed as planned, we initiated the Apertif FRB survey (ALERT).
Over the first 5 weeks we observed at design sensitivity in 2019, we
detected 5 new FRBs, and interferometrically localised each of these
to 0.4−10 sq. arcmin. All detections are broad band and very narrow,
of order 1 ms duration, and unscattered. Dispersion measures are
generally high. Please note that the ARTS DR1 collection available
from this end-point is superseded by the ARTS DR2 collection. DR2
includes all data from the DR1 collection that can be queried here.
The ARTS DR2 FRB observation cone search can be reached at
https://vo.astron.nl/arts_dr2/q/obs_cone/form.
We use type Ia supernova (SN Ia) data obtained by the Sloan Digital Sky Survey-II Supernova Survey (SDSS-II SNS) in combination with the publicly available SDSS DR16 fiber spectroscopy of supernova (SN) host galaxies to correlate SN Ia light-curve parameters and Hubble residuals with several host galaxy properties. Fixed-aperture fiber spectroscopy suffers from aperture effects: the fraction of the galaxy covered by the fiber varies depending on its projected size on the sky, and thus measured properties are not representative of the whole galaxy. The advent of integral field spectroscopy has provided a way to correct the missing light, by studying how these galaxy parameters change with the aperture size. Here we study how the standard SN host galaxy relations change once global host galaxy parameters are corrected for aperture effects. We recover previous trends on SN Hubble residuals with host galaxy properties, but we find that discarding objects with poor fiber coverage instead of correcting for aperture loss introduces biases into the sample that affect SN host galaxy relations. The net effect of applying the commonly used g-band fraction criterion is that intrinsically faint SNe Ia in high-mass galaxies are discarded, thus artificially increasing the height of the mass step by 0.02 mag and its significance. Current and next-generation fixed-aperture fiber-spectroscopy surveys, such as DES, DESI, or TiDES in 4MOST, that aim to study SN and galaxy correlations must consider, and correct for, these effects.
We have studied the relationship between the star formation rate (SFR), surface density, and gas surface density in the spiral galaxy M51a (NGC 5194), using multiwavelength data obtained as part of the Spitzer Infrared Nearby Galaxies Survey (SINGS). We introduce a new SFR index based on a linear combination of Halpha emission-line and 24um continuum luminosities, which provides reliable extinction-corrected ionizing fluxes and SFR densities over a wide range of dust attenuations.
This study is the sixth of a series that investigates degeneracy and stochasticity problems present in the determination of the age, mass, extinction, and metallicity of partially resolved or unresolved star clusters in external galaxies when using Hubble Space Telescope broadband photometry. In the fifth publication, it was noticed that inconsistencies in cluster colour indices, which arise due to projected foreground and background stars on the apertures, enhance age-metallicity-extinction degeneracies. In this work we aim to present new aperture photometry results for a sample of star clusters from the M31 Panchromatic Hubble Andromeda Treasury (PHAT) survey. We employed two methods of aperture photometry. The first method is ordinary aperture photometry to measure total cluster fluxes. The second method was introduced to avoid the brightest foreground and background stars that project onto large apertures. This method employs smaller apertures, adapted to cover a central part of clusters, and applies an aperture correction, derived for the F475W passband, to other passbands.We note that this procedure is valid only for clusters without prominent systematic gradients of colour indices beyond half-light radii. We present two catalogues of star cluster aperture photometry (produced by applying ordinary aperture photometry and adaptive aperture photometry methods) with estimated uncertainties for a sample of 1181 star clusters from the M31 PHAT survey. Compared to the M31 PHAT fundamental star cluster aperture photometry catalogue published by Johnson et al., there are changes made in the following: cluster centre coordinates, aperture sizes, and sky background estimates.
We present aperture-synthesis imaging of the red supergiant Antares (alpha Sco) in the CO first overtone lines. Our goal is to probe the structure and dynamics of the outer atmosphere.
CK Vulpeculae (CK Vul) is an enigmatic star whose outburst was observed in 1670-72. A stellar-merger event was proposed to explain its ancient eruption. We aim to investigate the composition of the molecular gas recently discovered in the remnant of CK Vul. Deriving the chemical, elemental, and isotopic composition is crucial for identifying the nature of the object and obtaining clues on its progenitor(s). We observed millimeter and submillimeter-wave spectra of CK Vul using the IRAM 30m and APEX telescopes. Radiative-transfer modeling of the observed molecular features was performed to yield isotopic ratios for various elements. The spectra of CK Vul reveal a very rich molecular environment of low excitation (T_ex_~<12K). Atomic carbon and twenty seven different molecules, including two ions, were identified. They range from simple diatomic to complex polyatomic species of up to seven atoms large. The chemical composition of the molecular gas is indicative of carbon and nitrogen-driven chemistry but oxides are also present. Additionally, the abundance of F may be enhanced. The spectra are rich in isotopologues that are very rare in most known sources. All stable isotopes of C, N, O, Si, and S are observed and their isotopic ratios are derived. The composition of the remnant's molecular gas is most peculiar and gives rise to a very unique millimeter and submillimeter spectrum. The observation of ions and complex molecules suggests the presence of a photoionizing source but its nature (a central star or shocks) remains unknown. The elemental and isotopic composition of the gas cannot be easily reconciled with standard nucleosynthesis but processing in hot CNO cycles and partial He burning can explain most of the chemical peculiarities. The isotopic ratios of CK Vul are remarkably close to those of presolar nova grains but the link of Nova 1670 to objects responsible for these grains is unclear.
