6 research outputs found
Treasurehunt: Transients and variability discovered with HST in the JWST North Ecliptic Pole time-domain field
The James Webb Space Telescope (JWST) North Ecliptic Pole (NEP) Time-domain Field (TDF) is a >14' diameter field optimized for multiwavelength time-domain science with JWST. It has been observed across the electromagnetic spectrum both from the ground and from space, including with the Hubble Space Telescope (HST). As part of HST observations over three cycles (the "TREASUREHUNT" program), deep images were obtained with the Wide Field Camera on the Advanced Camera for Surveys in F435W and F606W that cover almost the entire JWST NEP TDF. Many of the individual pointings of these programs partially overlap, allowing an initial assessment of the potential of this field for time-domain science with HST and JWST. The cumulative area of overlapping pointings is ā¼88 arcmin2, with time intervals between individual epochs that range between 1 day and 4+ yr. To a depth of mAB ā 29.5 mag (F606W), we present the discovery of 12 transients and 190 variable candidates. For the variable candidates, we demonstrate that Gaussian statistics are applicable and estimate that ā¼80 are false positives. The majority of the transients will be supernovae, although at least two are likely quasars. Most variable candidates are active galactic nuclei (AGNs), where we find 0.42% of the general z ā² 6 field galaxy population to vary at the ā¼3Ļ level. Based on a 5 yr time frame, this translates into a random supernova areal density of up to ā¼0.07 transients arcminā2 (ā¼245 degā2) per epoch and a variable AGN areal density of ā¼1.25 variables arcminā2 (ā¼4500 degā2) to these depths
Recommended from our members
Magellanic System Stars Identified in SMACS J0723.3-7327 James Webb Space Telescope Early Release Observations Images
We identify 71 distant stars in James Webb Space Telescope/NIRCam early release observations (ERO) images of the field of galaxy cluster SMACS J0723.3-7327 (SMACS 0723). Given the relatively small (ā¼10Ā°) angular separation between SMACS 0723 and the Large Magellanic Cloud (LMC), it is likely that these stars are associated with the LMC outskirts or the Leading Arm. This is further bolstered by a spectral energy distribution (SED) analysis, which suggests an excess of stars at a physical distance of 40-100 kpc, consistent with being associated with or located behind the Magellanic system. In particular, we find that the overall surface density of stars brighter than 27.0 mag in the field of SMACS 0723 is ā¼2.3 times that of stars in a blank field with similar Galactic latitude (the North Ecliptic Pole Time Domain Field), and that the density of stars in the SMACS 0723 field with SED-derived distances consistent with the Magellanic system is ā¼6.1 times larger than that of the blank field. The candidate stars at these distances are consistent with a stellar population at the same distance modulus with [Fe/H] = ā1.0 and an age of ā¼5.0 Gyr. On the assumption that all of the 71 stars are associated with the LMC, then the stellar density of the LMC at the location of the SMACS 0723 field is ā¼740 stars kpcā3, which helps trace the density of stars in the LMC outskirts. Ā© 2023. The Author(s). Published by the American Astronomical Society.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]
Recommended from our members
JWST's PEARLS: Transients in the MACS J0416.1ā2403 Field
With its unprecedented sensitivity and spatial resolution, the James Webb Space Telescope (JWST) has opened a new window for time-domain discoveries in the infrared. Here we report observations in the only field that has received four epochs (spanning 126 days) of JWST NIRCam observations in Cycle 1. This field is toward MACS J0416.1ā2403, which is a rich galaxy cluster at redshift z = 0.4 and is one of the Hubble Frontier Fields. We have discovered 14 transients from these data. Twelve of these transients happened in three galaxies (with z = 0.94, 1.01, and 2.091) crossing a lensing caustic of the cluster, and these transients are highly magnified by gravitational lensing. These 12 transients are likely of a similar nature to those previously reported based on the Hubble Space Telescope (HST) data in this field, i.e., individual stars in the highly magnified arcs. However, these 12 could not have been found by HST because they were too red and too faint. The other two transients are associated with background galaxies (z = 2.205 and 0.7093) that are only moderately magnified, and they are likely supernovae. They indicate a demagnified supernova surface density, when monitored at a time cadence of a few months to a ā¼3-4 Ī¼m survey limit of AB ā¼28.5 mag, of ā¼0.5 arcminā2 integrated to z ā 2. This survey depth is beyond the capability of HST but can be easily reached by JWST. Ā© 2023. The Author(s). Published by the American Astronomical Society.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]
Recommended from our members
PEARLS: JWST Counterparts of Microjansky Radio Sources in the Time Domain Field
The Time Domain Field (TDF) near the North Ecliptic Pole in JWSTās continuous-viewing zone will become a premier āblank fieldā for extragalactic science. JWST/NIRCam data in a 16 arcmin2 portion of the TDF identify 4.4 Ī¼m counterparts for 62 of 63 3 GHz sources with S(3 GHz) > 5 Ī¼Jy. The one unidentified radio source may be a lobe of a nearby Seyfert galaxy, or it may be an infrared-faint radio source. The bulk properties of the radio-host galaxies are consistent with those found by previous work: redshifts range from 0.14-4.4 with a median redshift of 1.33. The radio emission arises primarily from star formation in ā¼2/3 of the sample and from an active galactic nucleus (AGN) in ā¼1/3, but just over half the sample shows evidence for an AGN either in the spectral energy distribution or by radio excess. All but three counterparts are brighter than magnitude 23 AB at 4.4 Ī¼m, and the exquisite resolution of JWST identifies correct counterparts for sources for which observations with lower angular resolution would misidentify a nearby bright source as the counterpart when the correct one is faint and red. Up to 11% of counterparts might have been unidentified or misidentified absent NIRCam observations. Ā© 2023. The Author(s). Published by the American Astronomical Society.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]
Recommended from our members
The JWST Discovery of the Triply Imaged Type Ia āSupernova H0peā and Observations of the Galaxy Cluster PLCK G165.7+67.0
A Type Ia supernova (SN) at z = 1.78 was discovered in James Webb Space Telescope Near Infrared Camera imaging of the galaxy cluster PLCK G165.7+67.0 (G165; z = 0.35). The SN is situated 1.5-2 kpc from the host-galaxy nucleus and appears in three different locations as a result of gravitational lensing by G165. These data can yield a value for Hubbleās constant using time delays from this multiply imaged SN Ia that we call āSN H0pe.ā Over the cluster, we identified 21 image multiplicities, confirmed five of them using the Near-Infrared Spectrograph, and constructed a new lens model that gives a total mass within 600 kpc of (2.6 Ā± 0.3) Ć 1014 M ā. The photometry uncovered a galaxy overdensity coincident with the SN host galaxy. NIRSpec confirmed six member galaxies, four of which surround the SN host galaxy with relative velocity ā²900 km sā1 and projected physical extent ā²33 kpc. This compact galaxy group is dominated by the SN host galaxy, which has a stellar mass of (5.0 Ā± 0.1) Ć 1011 M ā. The group members have specific star formation rates of 2-260 Gyrā1 derived from the HĪ±-line fluxes corrected for stellar absorption, dust extinction, and slit losses. Another group centered on a strongly lensed dusty star-forming galaxy is at z = 2.24. The total (unobscured and obscured) SFR of this second galaxy group is estimated to be (ā³ 100 M ā yrā1), which translates to a supernova rate of ā¼1 SNe yrā1, suggesting that regular monitoring of this cluster may yield additional SNe. Ā© 2024. The Author(s). Published by the American Astronomical Society.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]
Recommended from our members
JWST PEARLS. Prime Extragalactic Areas for Reionization and Lensing Science: Project Overview and First Results
We give an overview and describe the rationale, methods, and first results from NIRCam images of the JWST āPrime Extragalactic Areas for Reionization and Lensing Scienceā (PEARLS) project. PEARLS uses up to eight NIRCam filters to survey several prime extragalactic survey areas: two fields at the North Ecliptic Pole (NEP); seven gravitationally lensing clusters; two high redshift protoclusters; and the iconic backlit VV 191 galaxy system to map its dust attenuation. PEARLS also includes NIRISS spectra for one of the NEP fields and NIRSpec spectra of two high-redshift quasars. The main goal of PEARLS is to study the epoch of galaxy assembly, active galactic nucleus (AGN) growth, and First Light. Five fieldsāthe JWST NEP Time-Domain Field (TDF), IRAC Dark Field, and three lensing clustersāwill be observed in up to four epochs over a year. The cadence and sensitivity of the imaging data are ideally suited to find faint variable objects such as weak AGN, high-redshift supernovae, and cluster caustic transits. Both NEP fields have sightlines through our Galaxy, providing significant numbers of very faint brown dwarfs whose proper motions can be studied. Observations from the first spoke in the NEP TDF are public. This paper presents our first PEARLS observations, their NIRCam data reduction and analysis, our first object catalogs, the 0.9-4.5 Ī¼m galaxy counts and Integrated Galaxy Light. We assess the JWST sky brightness in 13 NIRCam filters, yielding our first constraints to diffuse light at 0.9-4.5 Ī¼m. PEARLS is designed to be of lasting benefit to the community. Ā© 2022. The Author(s). Published by the American Astronomical Society.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]