J/ApJ/905/58 The local universe with ZTF. I. Ca-rich gap transients (De+, 2020)
The Zwicky Transient Facility Census of the Local Universe.
I. Systematic search for calcium-rich gap transients reveals three related
spectroscopic subclasses.
De K., Kasliwal M.M., Tzanidakis A., Fremling U.C., Adams S., Aloisi R.,
Andreoni I., Bagdasaryan A., Bellm E.C., Bildsten L., Cannella C.,
Cook D.O., Delacroix A., Drake A., Duev D., Dugas A., Frederick S.,
Gal-Yam A., Goldstein D., Golkhou V.Z., Graham M.J., Hale D., Hankins M.,
Helou G., Ho A.Y.Q., Irani I., Jencson J.E., Kaplan D.L., Kaye S.,
Kulkarni S.R., Kupfer T., Laher R.R., Leadbeater R., Lunnan R., Masci F.J.,
Miller A.A., Neill J.D., Ofek E.O., Perley D.A., Polin A., Prince T.A.,
Quataert E., Reiley D., Riddle R.L., Rusholme B., Sharma Y., Shupe D.L.,
Sollerman J., Tartaglia L., Walters R., Yan L., Yao Y.
<Astrophys. J., 905, 58 (2020)>
=2020ApJ...905...58D 2020ApJ...905...58D
ADC_Keywords: Supernovae; Photometry, ugriz; Spectra, optical; Redshifts;
Magnitudes, absolute; Surveys
Keywords: Supernovae ; Compact objects ; White dwarf stars
Abstract:
Using the Zwicky Transient Facility alert stream, we are conducting a
large spectroscopic campaign to construct a complete, volume-limited
sample of transients brighter than 20mag, and coincident within 100"
of galaxies in the Census of the Local Universe catalog. We describe
the experiment design and spectroscopic completeness from the first
16 months of operations, which have classified 754 supernovae. We
present results from a systematic search for calcium-rich gap
transients in the sample of 22 low-luminosity (peak absolute magnitude
M>-17), hydrogen-poor events found in the experiment. We report the
detection of eight new events, and constrain their volumetric rate to
≳15%±5% of the SN Ia rate. Combining this sample with 10 previously
known events, we find a likely continuum of spectroscopic properties
ranging from events with SN Ia-like features (Ca-Ia objects) to those
with SN Ib/c-like features (Ca-Ib/c objects) at peak light. Within the
Ca-Ib/c events, we find two populations distinguished by their red
(g-r∼1.5mag) or green (g-r∼0.5mag) colors at the r-band peak, wherein
redder events show strong line blanketing features and slower light
curves (similar to Ca-Ia objects), weaker He lines, and lower
[CaII]/[OI] in the nebular phase. We find that all together the
spectroscopic continuum, volumetric rates, and striking old
environments are consistent with the explosive burning of He shells on
low-mass white dwarfs. We suggest that Ca-Ia and red Ca-Ib/c objects
arise from the double detonation of He shells, while green Ca-Ib/c
objects are consistent with low-efficiency burning scenarios like
detonations in low-density shells or deflagrations.
Description:
The Zwicky Transient Facility (ZTF) is a wide-field optical
time-domain survey running out of the 48 inch Schmidt telescope (P48)
at Palomar Observatory.
The ZTF Census of the Local Universe (CLU) experiment has been
designed to build up a spectroscopically classified sample of
transients in the local universe (within 200Mpc) by classifying all
transients found coincident with galaxies in the CLU
(Cook+ 2019, J/ApJ/880/7) catalog. The CLU experiment was initiated on
2018 June 1 and we restrict the sample of transients in this paper to
events saved until 2019 September 30.
Selected sources were assigned for spectroscopic follow-up on the
Double Beam Spectrograph (DBSP) on the 200 inch Hale telescope (P200)
at Palomar Observatory. We also used the Low Resolution Imaging
Spectrometer (LRIS) on the Keck I telescope for spectroscopic
classifications. See Section 2.
We obtained gri photometry of the transients from data taken with the
P48 ZTF camera. We obtained additional multi-color photometry near
peak light with the SEDM rainbow camera on the Palomar 60 inch
telescope. See Section 2.4.
We obtained additional late-time photometry of the transients with the
Wafer-scale Imager for Prime (WaSP) on the Palomar 200 inch telescope.
We used LRIS on the Keck I telescope for late-time imaging of some
transients reported in this paper. See Section 2.5.
Spectroscopic follow-up of transients near peak light was obtained as
a part of the regular classification effort of the CLU experiment.
The SEDM spectrograph was used for spectroscopy for only two of these
sources (SN 2018gwo and SN 2019hty) since they were typically too
faint (>19mag) for SEDM spectroscopy. We obtained two epochs of
spectroscopy of SN 2018gwo with the APLY200 spectrograph at Three
Hills Observatory. We obtained follow-up spectroscopy for some sources
using the Alhambra Faint Object Spectrograph and Camera (ALFOSC) on
the Nordic Optical Telescope (NOT).
Late-time nebular spectroscopy was obtained using LRIS on the Keck I
telescope starting from ∼30 days after peak light. For some sources,
we obtained up to four epochs of nebular-phase spectra using LRIS.
See Section 2.6.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 120 63 Summary of the properties of the 22 faint
hydrogen-poor transients selected for nebular phase
follow-up in this work (+ SN2018gwo)
table2.dat 50 991 Photometry of all the sources presented in this paper
table4.dat 73 77 Spectral fit parameters for the sample of Ca-rich
gap transients presented in this paper, together
with the fits for the literature sample of Ca-rich
gap transients
table5.dat 98 43 Light curve fit parameters for the sample of Ca-rich
gap transients presented in this paper, together
with the fits for the literature sample of Ca-rich
gap transients
fig5.dat 53 100964 Spectroscopic sequence of the sample of Ca-rich gap
transients presented in this paper
fig29.dat 53 151100 Photospheric and nebular phase spectrum of objects
in the control sample that did not pass either the
early nebular-phase transition criterion or the
nebular-phase [CaII]/[OI] threshold
--------------------------------------------------------------------------------
See also:
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
VII/195 : Globular Clusters in the Milky Way (Harris, 1996)
VII/202 : Globular Clusters in the Milky Way (Harris, 1997)
VII/281 : GLADE v2.3 catalog (Dalya+, 2018)
J/ApJ/560/566 : K-band galaxy LF from 2MASS (Kochanek+, 2001)
J/ApJ/696/870 : Catalina Real-time Transient Survey (CRTS) (Drake+, 2009)
J/ApJ/707/1449 : Local hosts of SNe Ia (Neill+, 2009)
J/ApJ/741/97 : Light curves of Ibc supernovae (Drout+, 2011)
J/MNRAS/412/1441 : SNe luminosity functions (Li+, 2011)
J/MNRAS/425/1789 : Berkeley supernova Ia program. I. (Silverman+, 2012)
J/MNRAS/429/2143 : Hidden population of AM CVns in the SDSS (Carter+, 2013)
J/A+A/593/A68 : PTF12os & iPTF13bvn spectra & light curves (Fremling+, 2016)
J/ApJ/827/90 : Spectroscopy of SNe Ib, IIb and Ic (Liu+, 2016)
J/ApJ/836/60 : Bgri light curves of PTF11kmb and PTF12bho (Lunnan+, 2017)
J/other/Sci/362.201 : iPTF 14gqr (SN 2014ft) photometry (De+, 2018)
J/A+A/618/A37 : Sp. log of (i)PTF stripped-envelope SN (Fremling+, 2018)
J/ApJ/880/7 : Census of the Local Universe survey. I. (Cook+, 2019)
J/A+A/630/A76 : SN2016hnk photometry and spectroscopy (Galbany+, 2019)
J/A+A/631/A147 : Transient processing & analysis using AMPEL (Nordin+, 2019)
J/ApJ/886/152 : ZTF early observations of Type Ia SNe. I. LCs (Yao+, 2019)
J/ApJ/896/165 : Optical light curves of SN 2016hnk (Jacobson-Galan+, 2020)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 A3 --- --- [ZTF]
5- 13 A9 --- ZTF ZTF identifier
15- 23 A9 --- Name SN name
25 A1 --- f_Name [*] Flag on SN 2018gwo (1)
27- 28 I2 h RAh Hour of right ascension (J2000)
30- 31 I2 min RAm Minute of right ascension (J2000)
33- 37 F5.2 s RAs Second of right ascension (J2000)
39 A1 --- DE- Sign of declination (J2000)
40- 41 I2 deg DEd Degree of declination (J2000)
43- 44 I2 arcmin DEm Arcminute of declination (J2000)
46- 50 F5.2 arcsec DEs Arcsecond of declination (J2000)
52- 61 A10 --- SpT Spectral type (2)
63 A1 --- l_rMAG Limit flag on rMAG
65- 70 F6.2 mag rMAG [-17.03/-13.9] Absolute r-band magnitude
72 A1 --- l_FCa/OI Limit flag on FCa/OI
74- 78 F5.2 --- FCa/OI ? [CaII]/[OI] flux ratio
79- 80 A2 --- n_FCa/OI Note on FCa/OI (3)
82- 85 I4 --- Phase [16/357] Phase
87- 91 F5.3 --- z [0.006/0.045] Redshift
93- 97 F5.2 arcsec Sep1 [1.3/54.2] Host offset in arcsec
99- 103 F5.2 kpc Sep2 [0.6/26.7] Host offset in kpc
105- 114 A10 "Y/M/D" Date Observation date;
column added by CDS from Fig 5 and 29
116- 120 A5 --- Tel Telescope;
column added by CDS from Fig 5 and 29 (G1)
--------------------------------------------------------------------------------
Note (1):
* = In the case of SN 2018gwo, the object did not pass the primary
selection criteria but is a likely Ca-rich gap transient when we
combined publicly available photometry and nebular-phase follow-up
from our campaign.
Note (2): Only refers to the spectroscopic appearance of the object near peak
light. The Ca-rich objects are indicated with "Ca".
Note (3): For cases where the object did not turn nebular even at the latest
phases of spectroscopic follow-up, we indicate the [CaII]/[OI] flux
ratio with "NN" and indicate the phase of the latest available spectrum.
Details on the objects that did not pass the nebular-phase criterion
are discussed in Appendix, highlighting why each object was excluded
from the Ca-rich sample.
For one event (SN 2019gau), we did not detect nebular emission
features ("NE").
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 A9 --- Name SN name
11- 18 F8.2 d MJD [58242.23/58931.3] Modified Julian Date
20- 25 F6.2 d Phase [-39.43/545] Rest frame phase; days from r peak
27 A1 --- Filt [gri] Filter used
29 A1 --- l_mag 5σ upper limit at the transient location
30- 34 F5.2 mag mag [15.83/26.5] Apparent magnitude in Filt
not corrected for Galactic extinction
36- 40 F5.2 mag e_mag [0.01/0.4]?=99 Uncertainty in mag
42- 50 A9 --- Inst Instrument used (1)
--------------------------------------------------------------------------------
Note (1): Instrument as follows:
P48+ZTF = Zwicky Transient Facility (ZTF) using the 48 inch Schmidt telescope
at Palomar Observatory (918 occurrences)
P60+SEDM = The robotic Spectral Energy Distribution Machine (53 occurrences)
Keck+LRIS = the Low Resolution Imaging Spectrometer on the Keck I telescope
(12 occurrences)
P200+WASP = the Wafer-scale Imager for Prime (WaSP) on the Palomar 200 inch
telescope (8 occurrences)
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 A9 --- Name SN name
11 A1 --- n_Name SN name (1)
13- 16 I4 d Phase [-8/265] Time since maximum
18- 22 I5 km/s V1 [3620/15010]?=-99 The HeI 5876Å velocity
24- 27 I4 km/s e_V1 [40/1140]?=-99 Uncertainty in V1
29- 32 I4 0.1nm W1 [5800/5876]?=-99 Wavelength of the measured V1 line
34- 38 I5 km/s V2 [2470/11120]?=-99 The HeI 7065Å/SiII 6355Å
velocity
40- 42 I3 km/s e_V2 [20/760]?=-99 Uncertainty in V2
44- 47 I4 0.1nm W2 [6355/7065]?=-99 Wavelength of the measured V2
49 A1 --- l_Ratio Lower limit on Ratio where [OI] is not detected
(see text)
51- 56 F6.2 --- Ratio [2.1/22.35]?=-99 Measured [CaII]/[OI] ratio
58- 63 F6.2 --- e_Ratio [0.05/4.4]?=-99 Uncertainty in Ratio
65- 73 A9 --- Ref Reference (G2)
--------------------------------------------------------------------------------
Note (1):
n= The signal to noise ratio of the spectrum was not high enough in the
V2 measurements for SN 2018lqu at Phase=+31 and SN 2019pxu at Phase=+0
and the V1 measurements for SN 2018kjy at Phase=+1 to be measured.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table5.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 A9 --- Name SN name
11- 12 A2 --- Filt [BVRIGgrizg'r' ] Filter used
14- 21 F8.2 d tpk [53387.15/58747.78] Modified Julian Date of peak
time in Filt
23- 28 F6.2 d e_tpk [0.2/3.2]?=-99 Uncertainty in tpk
30- 34 F5.2 mag magpk [16.2/20.3] Peak apparent magnitude in Filt (1)
36- 39 F4.2 mag e_magpk [0.01/0.3] Uncertainty in magpk
41- 46 F6.2 mag MAGpk [-17.1/-13.42] Peak absolute magnitude in Filt
48- 53 F6.2 d tr0.5 [5.8/8.81]?=-99 Rise time to peak from half peak
flux
55- 60 F6.2 d e_tr0.5 [0.2/1.8]?=-99 Uncertainty in tr0.5
62- 67 F6.2 d tf0.5 [5/15.3]?=-99 Fall time from peak to half peak
flux
69- 74 F6.2 d e_tf0.5 [0.3/3.2]?=-99 Uncertainty in tf0.5
76- 81 F6.2 mag Delm7 [0.09/0.8]?=-99 Magnitude drop after 7 days post
peak
83- 88 F6.2 mag e_Delm7 [0.02/0.5]?=-99 Uncertainty in Delm7
90- 98 A9 --- Ref Reference (G2)
--------------------------------------------------------------------------------
Note (1): Corrected for Galactic extinction using the maps of
Schlafly & Finkbeiner (2011ApJ...737..103S 2011ApJ...737..103S).
--------------------------------------------------------------------------------
Byte-by-byte Description of file: fig5.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 A3 --- --- [ZTF]
4- 12 A9 --- ZTF ZTF identifier (see the corresponding
SN name in Table 1)
14- 23 A10 "Y/M/D" Date Observation date
25- 29 A5 --- Tel Facility identifier (G1)
31- 40 F10.4 0.1nm lambda [3056.1/10309.4] Wavelength; Angstroms
42- 53 E12.5 --- Flux [-0.045/1.8]? Flux density (1)
--------------------------------------------------------------------------------
Note (1): In units of erg/s/cm2/Angstroms except for data obtained THO
which are relative.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: fig29.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 A3 --- --- [ZTF]
4- 12 A9 --- ZTF ZTF identifier (see the corresponding
SN name in Table 1)
14- 23 A10 "Y/M/D" Date Observation date
25- 29 A5 --- Tel Facility identifier (G1)
31- 40 F10.4 0.1nm lambda [3056/10499.8] Wavelength; Angstroms
42- 53 E12.5 cW/m2/nm Flux [-1.3e-15/1.7e-14]? Flux density;
in erg/s/cm2/Å units
--------------------------------------------------------------------------------
Global notes:
Note (G1): Telescope as follows:
P200 = 200-inch Hale telescope at Palomar observatory
Keck1 = Keck-I telescope
THO = Three Hills observatory
P60 = 60-inch telescope at Palomar observatory
Note (G2): Reference as follows:
1 = Perets et al. (2010Natur.465..322P 2010Natur.465..322P);
2 = Sullivan et al. (2011ApJ...732..118S 2011ApJ...732..118S);
3 = Kasliwal et al. (2012ApJ...755..161K 2012ApJ...755..161K);
4 = Valenti et al. (2014MNRAS.437.1519V 2014MNRAS.437.1519V);
5 = Lunnan et al. (2017, J/ApJ/836/60);
6 = De et al. (2018ApJ...866...72D 2018ApJ...866...72D);
7 = Galbany et al. (2019, J/A+A/630/A76);
8 = Jacobson-Galan et al. (2019, J/ApJ/896/165).
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Acknowledgements:
Kishalay De [kde1 at mit.edu]
History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 20-Jul-2022