UKIRT

The UKIRT Hemisphere Survey (UHS) is an ongoing large-area near-infrared Northern Hemisphere survey conducted using the Wide Field Camera (WFCAM). Its primary objective is to provide contiguous coverage between declinations of 0° and +60° by combining new imaging with previous UKIDSS surveys including the LAS, GPS and GCS.

DR2 was focused on the K-band observations but also contained a small amount of remaining or reobserved J-band observations. Similarly, DR3 was focused on H-band observations and contains a small amount of new or reobserved K-band observations. After accounting for deprecated frames and undergoing quality control the DR2 merged catalogue contains ~513 million sources. The DR3 merged catalogue contains ~560 million sources. Below are coverage maps of detections per square degree in H and K-bands respectively. Areas previously covered by UKIDSS LAS, GPS and GCS are indicated on both.

You can see a current coverage chart in each band individually or altogether at this link: http://casu.ast.cam.ac.uk/wfcamsp/uhs

The figure above depicts distance modulus versus redshift for a subset of the Hawai’i Supernova Flows sample with colors indicating predicted peculiar velocity from the 2M++ model. This survey will directly measure the component of Hubble scatter from peculiar velocities. UKIRT’s NIR coverage should reduce distance scatter by up to 30% and substantially reduce systemic uncertainties from dust reddening.

UKIRT has discovered a free-floating planetary mass brown dwarf, J050626.96+073842.4 (pictured above). J050626.96+073842.4 has the reddest known colors of any brown dwarf around L/T transition — young and very dusty atmosphere. Below is photometric data from the UHS survey and the USNO-UKIRT parallax.

UKIRT has assisted in the discovery of SPECULOOS-3 b—an earth-sized exoplanet in a 17 hour orbit around an M6.5-type dwarf star 16.8 parsecs away. A K-band transit light curve was obtained from UKIRT using the UKIRT Wide Field Camera (WFCAM) on two epochs. The exoplanet is suitable for spectroscopic studies from JWST.

Pictured above are the phase-folded transit light curves of SPECULOOS-3 b. The purple light curve at the bottom shows the K-band photometry obtained using UKIRT and WFCAM.

You can read the article at: https://www.researchsquare.com/article/rs-3678312/v1
or https://ui.adsabs.harvard.edu/link_gateway/2024NatAs…8..865G/EPRINT_PDF

From the UHS, UKIRT has ascertained the positions, photometry and proper motions for 966 known Brown Dwarfs. The measured proper motions are more precise than those from CatWISE and Pan-STARRS, but not Gaia – a valuable resource for non-Gaia point sources. The figure below is a comparison between the proper motion measurements and those from Gaia, CatWISE, and Pan-STARRS.

Using UKIRT Hemisphere Survey (UHS) data along with UKIDSS GPS and GCS data, and CatWise 2020 data, eight new substellar candidates in the Hyades cluster. All of these objects have been confirmed to be L6-T8 Brown Dwarfs with Gemini-GNIRS spectroscopy. The discovery of these objects has increased the number of T dwarfs in Hyades by 50%!

DEHVILS is the largest published NIR sample with consistent coverage of maximum light across three NIR bands (Y, J, H).

Type Ia supernova (SN Ia) distance measurements depend on the properties of their host galaxies, and recent work suggests that the diversity of reddening laws in SN host galaxies may be responsible. In UKIRT’s NIR bands, SN distances are less sensitive to dust and therefore this paper tests whether the mass step persists in these bands. It found: (i) further evidence for improved Hubble residuals in the NIR, (ii) the existence (or nonexistence) of the mass step in the NIR cannot be concluded upon at this time (even though others have claimed it can be), and (iii) Hubble residuals in the NIR and optical are well-correlated.

The figure above compares simulated mass steps with different dust assumptions to the data from DEHVILS (left) and previous work (right). The simulation values show the effect of achromatic SN scatter (blue) and scatter due to a spread in dust reddening models (orange), and are the same in both panels. The shaded regions show 1σ uncertainties from the data.

Conducted by the US Naval Observatory (USNO) in partnership with the UH IfA, Cambridge Astronomical Survey Unit, and the Wide-Field Astronomy Unit, ROE, Edinburgh using the UKIRT Wide Field Camera (WFCAM) covering the northern sky from 0 — +60° in declination (12,700 sq. degrees), UHS has data releases in J and more recently K-bands. Surveys done in H-band are nearly complete with a new survey of Y-band and a reobservation in J-band starting in late 2023. Regions previously covered in the UKIDSS sky survey have been excluded in the current rounds of the UHS survey.

You can see a current coverage chart in each band individually or altogether at this link: http://casu.ast.cam.ac.uk/wfcamsp/uhs