Supernova rates and luminosity functions from ASAS-SN II: 2014-2017 core-collapse supernovae and their subtypes

TL;DR

This paper delivers robust measurements of local core-collapse supernova (ccSN) rates and luminosity functions (LFs) using the untargeted ASAS-SN survey data from 2014–2017 in the V band, achieving high spectroscopic completeness. By employing injection-recovery simulations to quantify survey completeness and applying volume/time corrections, the authors obtain a total ccSN rate of $7.0^{+1.0}_{-0.9} imes 10^{-5}$ yr$^{-1}$ Mpc$^{-3}$ h$^{3}_{70}$ at a median redshift $z_{med}=0.0149$ for $M_{V,peak} \\leq -14$ mag, with a breakdown into subtypes showing Type II dominating the population. They also constrain the superluminous SN (SLSN) rate to the order of $1.5^{+4.4}_{-1.1}$ yr$^{-1}$ Gpc$^{-3}$ h$^{3}_{70}$ ( Gaia17biu; or $1.6^{+4.4}_{-1.1}$ including ASASSN-15lh) and find that ccSN rates decline with increasing luminosity, while the rate per unit stellar mass decreases toward higher-mass galaxies, suggesting metallicity and star-formation effects are at play. The intrinsic V-band LFs reveal a declining trend with luminosity across ccSNe and subtypes, and the results provide a precise local baseline for future ASAS-SN analyses in multiple bands and for environmental dependencies of ccSN progenitors.

Abstract

The volumetric rates and luminosity functions (LFs) of core-collapse supernovae (ccSN) and their subtypes are important for understanding the cosmic history of star formation and the buildup of ccSN products. To estimate these rates, we use data of nearby ccSNe discovered by the All-Sky Automated Survey for Supernovae (ASAS-SN) from 2014--2017, when all observations were made in the $V$-band. The sample is composed of 174 discovered or recovered events, with high spectroscopic completeness from followup observations. This allows us to obtain a statistically precise and systematically robust estimate of nearby rates for ccSNe and their subtypes. The volumetric rates are estimated by correcting the observed number of events for the survey completeness, which was estimated through injection recovery simulations using ccSN light curves. We find a total volumetric rate for ccSNe of $7.0^{+1.0}_{-0.9} \times 10^{-5} \ \textrm{yr}^{-1} \ \textrm{Mpc}^{-3} \ h^{3}_{70}$, at a median redshift of 0.0149, for absolute magnitudes at peak $M_{V,peak} \leq -14$ mag. This result is in agreement with previous local volumetric rates. We obtain volumetric rates for the different ccSN subtypes (II, IIn, IIb, Ib, Ic, Ibn, and Ic-BL), and find that the relative fractions of Type II, stripped-envelope, and interacting ccSNe are $63.2\%$, $32.3\%$, and $4.4\%$, respectively. We also estimate a volumetric rate for superluminous SNe of $1.5^{+4.4}_{-1.1} \ \textrm{yr}^{-1} \ \textrm{Gpc}^{-3} \ h^{3}_{70}$, corresponding to a fraction of $0.002\%$ of the total ccSN rate. We produce intrinsic $V$-band LFs of ccSNe and their subtypes, and show that ccSN rates steadily decline for increasing luminosities. We further investigate the specific ccSN rate as a function of their host galaxy stellar mass, and find that the rate decreases with increasing stellar mass, with significantly higher rates at lower mass galaxies.

Figures (12)

• Figure 1: Fractions of all the SNe and their subtypes discovered or recovered by ASAS-SN between 2014 and 2017 2017MNRAS.467.1098H2017MNRAS.471.4966H2017MNRAS.464.2672H2019MNRAS.484.1899H. This sample is $97\%$ spectroscopically complete.
• Figure 2: Equatorial coordinates of all the ccSNe discovered or recovered by ASAS-SN between 2014 and 2017 (red stars). The ccSNe are shown over the survey sky footprint in the same period. The color bar shows the number of images for individual observations in different areas of the sky.
• Figure 3: Distribution of apparent (top) and absolute magnitude (bottom) at peak brightness for the 207 events in the initial sample. We restrict the sample to events with $m_{V, peak} \leq 17.0$ and $17.5$ mag, $M_{V, peak} \leq -14.0$ mag, and $z_{min} \geq 0.001$ (dashed lines). The open circles correspond to the excluded 33 SNe, and the filled circles correspond to the 174 SNe in the final sample.
• Figure 4: Completeness fractions for different ccSN templates as a function of peak apparent magnitude ($m_{V, peak}$). The vertical solid line shows the limiting magnitude of the analysis at $m_{V} = 17.0$ mag, while the vertical dashed line shows the limit used for light curves with long-duration plateaus at $m_{V} = 17.5$ mag.
• Figure 5: ccSN volumetric rate as a function of the minimum Galactic latitude ($b_{lim}$, top panel), minimum redshift ($z_{min}$, middle panel), and maximum apparent magnitude at peak ($m_{V,peak}$, bottom panel). The number of ccSNe included in each subsample is given in red, while the vertical dashed lines show the limits used for the final sample.