The ANDICAM-SOFI Near-infrared and Optical type Ia Supernova (ASNOS) sample: Description and data release

TL;DR

The ASNOS study expanding near-infrared SN Ia data presents 41 SNe Ia with 1,482 BVRIYJH epochs from ANDICAM and 125 JHK_s epochs from SOFI, all at z below 0.085, complemented by optical ZTF/ATLAS data. It provides a comprehensive data-reduction, photometry, template-subtraction, and light-curve fitting framework across SALT3-NIR, SNooPy, and BayeSN, along with host-galaxy SED modeling via HostPhot and Prospector. A companion cosmology paper will leverage these data to analyze Hubble residuals and SN-host correlations, using a flat $\\Lambda$CDM cosmology with $\\Omega_{m0}=0.3$ and $H_0=70$ km s$^{-1}$ Mpc$^{-1}$. The dataset increases publicly available NIR SN Ia measurements by ≈10%, and provides a detailed methodology and calibration pipeline, while noting limitations in template availability and Y-band calibration that influence certain bands.

Abstract

Type Ia supernovae (SNe Ia) provide the most robust means of measuring extragalactic distances. While most of the effort has focused on increasing the number of SNe Ia observed in the optical, near-infrared (NIR) observations remain scarce despite their advantages, that is, reduced dust extinction and a more intrinsic standard candle behavior, requiring little to no empirical corrections. Here, we present ASNOS (ANDICAM-SOFI Near-infrared and Optical type Ia Supernova), a dataset with sample size of 1,482 epochs in the $BVRIYJH$ filters from the ANDICAM instrument on the 1.3-meter SMARTS telescope at Cerro Tololo Inter-American Observatory, along with 125 $JHK$ epochs from the SOFI instrument on the 3.58-meter New Technology Telescope on the La Silla Observatory. Additionally, we incorporate optical forced photometry from the Zwicky Transient Facility and the Asteroid Terrestrial-impact Last Alert System. The sample comprises 41 SNe Ia in total, including 29 normal events, eight 1991T-like objects, and four peculiar subtypes, all located at redshifts $z < 0.085$. This paper provides a detailed overview of the ASNOS sample selection, data reduction, SN photometry, host-galaxy spectral energy distribution construction, both global and local, and SN light-curve fitting using three methods: SALT3-NIR, SNooPy, and BayeSN. A companion paper will present the cosmological analysis.

Figures (16)

• Figure 1: Example of raw image reduction for ANDICAM $J$-band image. Top row (left to right): Single raw image of SN 2019so, master dark, dark reduced raw image using the two previous images and master flat. Middle row: Flat and dark reduced image, detected cosmic rays, cosmic ray corrected image and quadrant background level. Bottom row: Image corrected for quadrant features, sky image, and sky subtracted image. The sky image was evaluated from the remaining set of dithered images taken on the same night. The host galaxy was masked out for each single image when constructing the sky image.
• Figure 2: Example of background subtraction for a SOFI image. Left: Combined $J$-band science image of SN 2018agk taken with SOFI. Middle: Detected image background using photutils.Background2D. Right: Background and cosmic ray subtracted image. It is seen that we were able to remove most quadrant structure of the image.
• Figure 3: Template subtraction using ImageMatch. Left: Science image without template subtraction. Middle: Fully subtracted science image. Right: Template subtracted image using ImageMatch with the SN in the middle of the subtracted area. ImageMatch does subtraction on the full image, but one can choose to have the subtracted area around the SN inserted back into the original science image, which allowed us to use local sequence stars to determine zeropoints.
• Figure 4: Example of measuring $d_{DLR}$. The shape of the host was measured using $sep$ and plotted in orange. The $d_{DLR}$ is the ratio between distance from the host center to the SN (purple) and the distance from the host center to the edge of the ellipse (dashed blue).
• Figure 5: Top panels: Comparison of photometry using subtracted images (filled circles) vs. not using templates (empty circles) for SNe with different $d_{DLR}$. As expected, applying host-galaxy template subtraction to the science images did not have a huge effect on the light curve when the SN was far from its host ($d_{DLR}>1$). On the other hand, the effect was significant when $d_{DLR}<1$, showing why template subtractions were important. Bottom: Histogram of the apparent magnitude difference between subtracted and non-subtracted images. The median value is reported in the legend for each filter.