Examining he P ope ies o Low-luminosi y Hos s o Type Ia Supe no ae om ASAS-SN
Thomas W.-S. Holoien
1,20
, Ve a L. Be ge
1,2
, Jason T. Hinkle
3
, L. Galbany
4,5
, Allison L. S om
6,7
, Pa ick J. Vallely
8
,
Joseph P. Ande son
9
, Kons an ina Bou sia
10
, K. D. F ench
11
, Ch is ophe S. Kochanek
8,12,21
, Hanindyo Kunca ayak i
13,14
,
Joseph D. Lyman
15
, Nidia Mo ell
10
, Jose L. P ie o
16,17
, Sebas ián F. Sánchez
18
, K. Z. S anek
8,12
, and
G ego y L. Wal h
19
1
The Obse a o ies o he Ca negie Ins i u ion o Science, 813 San a Ba ba a S ., Pasadena, CA 91101, USA; [email p o ec ed]
2
Depa men o Physics and As onomy, Pomona College, 333 N. College Way, Cla emon , CA 91711, USA
3
Ins i u e o As onomy, Uni e si y o Hawaií, 2680 Woodlawn D i e, Honolulu, HI 96822, USA
4
Ins i u e o Space Sciences (ICE, CSIC), Campus UAB, Ca e de Can Mag ans, s/n, E-08193 Ba celona, Spain
5
Ins i u d’Es udis Espacials de Ca alunya (IEEC), E-08034 Ba celona, Spain
6
Depa men o As ophysical Sciences, P ince on Uni e si y, 4 I y La e, P ince on, NJ 08544, USA
7
Depa men o Physics and As onomy and Cen e o In e disciplina y Explo a ion and Resea ch in As ophysics (CIERA), No hwes e n Uni e si y, 2145 She idan
Road, E ans on, IL 60208, USA
8
Depa men o As onomy, The Ohio S a e Uni e si y, 140 Wes 18 h A enue, Columbus, OH 43210, USA
9
Eu opean Sou he n Obse a o y, Alonso de Có do a 3107, Casilla 19, San iago, Chile
10
Las Campanas Obse a o y, Ca negie Obse a o ies, Casilla 601, La Se ena, Chile
11
Depa men o As onomy, Uni e si y o Illinois, 1002 W. G een S ., U bana, IL 61801, USA
12
Cen e o Cosmology and As oPa icle Physics (CCAPP), The Ohio S a e Uni e si y, 191 W. Wood u A e., Columbus, OH 43210, USA
13
Tuo la Obse a o y, Depa men o Physics and As onomy, FI-20014 Uni e si y o Tu ku, Finland
14
Finnish Cen e o As onomy wi h ESO (FINCA), FI-20014 Uni e si y o Tu ku, Finland
15
Depa men o Physics, Uni e si y o Wa wick, Co en y, CV4 7AL, UK
16
Núcleo de As onomía de la Facul ad de Ingenie ía y Ciencias, Uni e sidad Diego Po ales, A . Ejé ci o 441, San iago, Chile
17
Millennium Ins i u e o As ophysics, San iago, Chile
18
Ins i u o de As onomía, Uni e sidad Nacional Au ónoma de Mexico, A.P. 70-264, C.P. 04510, México, D.F., Mexico
19
IPAC, Cali o nia Ins i u e o Technology, Mail Code 314-6, 1200 E. Cali o nia Bl d., Pasadena, CA 91125, USA
Recei ed 2022 July 8; e ised 2023 Ma ch 27; accep ed 2023 Ma ch 28; published 2023 June 14
Abs ac
We p esen a spec oscopic analysis o 44 low-luminosi y hos galaxies o Type Ia supe no ae (SNe Ia)de ec ed by
he All-Sky Au oma ed Su ey o Supe no ae (ASAS-SN), using hyd ogen, oxygen, and sul u emission lines o
measu e me allici ies and s a o ma ion a es. We find no s a is ically significan e idence ha he s a o ma ion
ac i i y and me allici ies o he galaxies in ou sample a e inconsis en wi h galaxies o simila luminosi ies and
masses. We iden i y wo 3σou lie galaxies ha ha e high me allici ies o hei s ella masses, bu find ha hei
o he p ope ies a e consis en wi h gene al galaxies. The o e all consis ency be ween ou sample and gene al
galaxy samples u he s eng hens he e idence om mo e luminous SN Ia hos galaxy samples ha SN Ia hos
galaxies a e ypical.
Unified As onomy Thesau us concep s: Type Ia supe no ae (1728);Supe no ae (1668);Galaxy abundances (574)
Suppo ing ma e ial: da a behind figu e, machine- eadable ables
1. In oduc ion
Type Ia supe no ae (SNe Ia)a e some o he mos ene ge ic
e en s in he Uni e se, and due o he empi ical ela ions
be ween hei in insic b igh ness and o he p ope ies, such as
decline a e and colo (e.g., Phillips 1993; Hamuy e al. 1996),
hey can be used as s anda dizable candles o measu e
cosmological dis ances. SNe Ia we e c ucial o he disco e y
o he accele a ing expansion o he Uni e se (Riess e al. 1998;
Pe lmu e e al. 1999). SNe Ia a e also use ul p obes o physics
unde ex eme condi ions, a e an end s age o s ella e olu ion,
and can significan ly impac he e olu ion o hei hos galaxy
en i onmen s (e.g., Maoz e al. 2012; Nomo o e al. 2013; Maoz
& G au 2017). The s udy o hese e en s hus impac s ou
unde s anding o a wide a ie y o as onomical subfields.
Despi e all his, he p ogeni o sys ems o SNe Ia a e s ill no
known, and hei physics a e no ully unde s ood (e.g., Shappee
e al. 2017,2018,2019; Vallely e al. 2019; Tucke e al. 2020).
The e is also di e si y in SNe Ia, wi h sub ypes exhibi ing
di e en luminosi ies and decline a es ha mus be accoun ed
o in o de o measu e hei dis ances accu a ely (e.g.,
Filippenko e al. 1992b,1992a; Phillips e al. 1992; Leibundgu
e al. 1993; Foley e al. 2013).
One way o s udy he physical causes o he di e ences in SN
Ia p ope ies and he possible dependence o hese di e ences
on p ogeni o p ope ies is o s udy he en i onmen s o SNe Ia.
P e ious s udies o SNe Ia and hei hos galaxies ha e e ealed
co ela ions be ween he b igh ness, decline a e, and expansion
a e o SNe Ia and he mo phology, mass, me allici y, s a
o ma ion a e (SFR), specific s a o ma ion a e (sSFR), and
colo o hei hos galaxies (e.g., Filippenko 1989; B anch &
an den Be gh 1993; Hamuy e al. 2000; Gallaghe e al. 2005,
2008; Howell e al. 2009; Lampei l e al. 2010; Sulli an e al.
2010; Uddin e al. 2017,2020; Kim e al. 2019; Smi h e al.
2020; Kelsey e al. 2021; Ponde e al. 2021; Popo ic e al.
2021). These co ela ions also hold, and a e ypically s onge ,
when examining he local en i onmen s a ound SNe, as
The As ophysical Jou nal, 950:108 (11pp), 2023 June 20 h ps://doi.o g/10.3847/1538-4357/acce35
© 2023. The Au ho (s). Published by he Ame ican As onomical Socie y.
20
NHFP Eins ein Fellow.
21
Radcli e Fellow.
O iginal con en om his wo k may be used unde he e ms o
he C ea i e Commons A ibu ion 4.0 licence. Any u he
dis ibu ion o his wo k mus main ain a ibu ion o he au ho (s)and he i le
o he wo k, jou nal ci a ion and DOI.
1
opposed o global galaxy p ope ies (e.g., Rigaul e al. 2013,
2015,2020; Ande son e al. 2015; Jones e al. 2015,2018;
Mo eno-Raya e al. 2016a,2016b; Galbany e al. 2018; Kim
e al. 2018,2019; Roman e al. 2018; Rose e al. 2019; Kelsey
e al. 2021). This implies ha one o mo e p ope ies o SN Ia
p ogeni o s ha a e co ela ed wi h hos galaxy p ope ies a e
esponsible o some o he obse ed di e si y in SN Ia ligh
cu es.
P e ious s udies o he p ope ies o SN Ia hos galaxies ha e
ound ha SN Ia hos s a e gene ally consis en wi h he gene al
popula ion o galaxies. In pa icula , Child ess e al. (2013)
pe o med bo h a pho ome ic and spec oscopic s udy o SN Ia
hos s using he sample om he Nea by Supe no a Fac o y
(Alde ing e al. 2002). They ound ha SN Ia hos s had s a
o ma ion ac i i y and me allici ies ep esen a i e o no mal
galaxies, as had been ound in p e ious wo k on pho ome ic
p ope ies, such as mass (e.g., Howell e al. 2009; Neill e al.
2009). These and ea lie s udies o SN Ia hos s la gely ocused
on highe -mass, highe -luminosi y hos galaxies. This is likely a
byp oduc o ea lie SN su eys being biased owa d ce ain
ypes o hos s due o obse ing s a egy and/o su ey design,
and by a lack o ollow-up esou ces o obse e ain e , low-
luminosi y hos galaxies in significan numbe s.
In ecen yea s, he p oli e a ion o la ge-a ea, apid-cadence
su eys, such as he All-Sky Au oma ed Su ey o Supe no ae
(ASAS-SN; Shappee e al. 2014), he As e oid Te es ial-
impac Las Ale Sys em (Ton y e al. 2018), and he Zwicky
T ansien Facili y (Bellm e al. 2019), has esul ed in la ge
samples o SNe ee om many o he hos -dependen biases o
ea lie SN su eys. This has allowed SN p ope ies and a es o
be co ela ed wi h hos p ope ies a much b oade anges han
we e p e iously possible. Fo example, B own e al. (2019)
used he ASAS-SN sample o ex end he obse ed end in he
specific SN Ia a e wi h espec o hos galaxy mass o oughly
h ee o de s o magni ude lowe in mass han in Kis le e al.
(2013), who used he Lick Obse a o y Supe no a Sea ch
(Li e al. 2000)sample. These mode n samples, pa icula ly
nea by ones om b igh -sky su eys, such as ASAS-SN, a e
hus ideal o examining SN Ia hos galaxies a low luminosi ies
and masses. We can use hese samples o es whe he hese
hos s a e simila o he gene al popula ion o galaxies, as has
been seen wi h highe -mass and highe -luminosi y hos s.
This is impo an o es o mul iple easons. Fi s , i low-
luminosi y and low-mass SN Ia hos s di e om ypical
galaxies, his may a ec he p ogeni o s and p ope ies o SNe
Ia in hese galaxies. Unde s anding how he SNe Ia in hese
hos s may di e om hose in mo e ypical hos s will be
impo an o de eloping a ull physical unde s anding o SNe
Ia and hei explosion mechanisms. Second, i hese low-
luminosi y hos s do no ha e p ope ies simila o gene al
galaxies, i would mean ha s anda d galaxy ela ions, e.g., he
mass–me allici y ela ion, would no apply o his popula ion o
galaxies. P ope ies such as me allici y, which can only eliably
be measu ed using obse a ionally expensi e spec oscopy, a e
o en in e ed based on pho ome ically measu able p ope ies,
such as mass, when s udying SN Ia hos s (e.g., Howell e al.
2009; Neill e al. 2009). I low-luminosi y and low-mass hos s
de ia e om s anda d ela ions, i is c ucial o unde s and how
hey de ia e, so ha we can co ec ly accoun o he di e ences
when in e ing p ope ies such as me allici y in hese galaxies.
This pape p esen s a spec oscopic s udy o he p ope ies o
44 low-luminosi y SN Ia hos galaxies selec ed om he fi s 3
y o ASAS-SN. In Sec ion 2, we discuss he galaxies in ou
sample and how hey we e selec ed, he spec oscopic da a se ,
how we measu ed he emission line fluxes om he spec a, and
how we ansla ed hese line fluxes in o physical p ope ies. In
Sec ion 3, we analyze hese p ope ies and compa e hem o
se e al samples o non-SN hos galaxies. Finally, in Sec ion 4,
we discuss ou findings and he u u e di ec ions o his wo k.
Th oughou his pape , we assume a s anda d ΛCDM
cosmology, wi h H
0
=69.6 km s
−1
Mpc
−1
,Ω
M
=0.296, and
Ω
Λ
=0.714 (W igh 2006; Benne e al. 2014).
2. Low-luminosi y SN Ia Hos Galaxy Sample
2.1. Sample De ails
To selec a ep esen a i e sample o low-luminosi y hos
galaxies o SNe Ia, we fi s s a ed wi h he sample o SN Ia used
by B own e al. (2019) o measu e he ela i e specific SN Ia a e
om he fi s 3 y o ASAS-SN. The ASAS-SN sample is ideal
o a numbe o easons: ASAS-SN su eys he en i e sky
sys ema ically, meaning he e is no bias owa d a p e iously
selec ed sample o galaxies o owa d galaxies o a pa icula
luminosi y; ASAS-SN su eys he nea by Uni e se, meaning
low-luminosi y galaxies in he ASAS-SN sample should be
close enough o obse e spec oscopically; and he ASAS-SN
sample was small enough o all possible SNe o be obse ed
spec oscopically, lowe ing he likelihood o an SN being
missed due o limi ed esou ces.
F om he B own e al. (2019)sample we selec ed galaxies
wi h LLlog 1.5
-, calcula ing he luminosi y o he
galaxies based on he K
S
-band magni udes om Holoien e al.
(2017a)and assuming M24.2
K,S
=- (Kochanek e al. 2001).
This esul ed in a sample o 58 low-luminosi y SN Ia hos
galaxies ha we a ge ed o spec oscopic obse a ion. The
final sample p esen ed he e comp ises 44 o hese galaxies, o
which we we e able o ob ain spec a wi h high enough signal-
o-noise a ios (S/Ns) o measu e he emission line fluxes
needed o ou analyses. These a e p ima ily Hα,Hβ, he [OIII]
λ4959/5007 double , and he [NII]λ6548/6583 double ,
hough we also measu e se e al o he s when possible. Ou
educed spec a a e a ailable in he online jou nal. Fo
comple eness, he spec a a ailable online also include he
educed spec a o nine addi ional galaxies ha we e obse ed,
bu a e no included in ou analyses, as hey did no yield well-
measu ed emission line fluxes.
Figu e 1shows his og ams o he edshi s, s ella masses,
and luminosi ies o he galaxies in ou sample compa ed o he
ull sample om B own e al. (2019). Ou sample is composed
o he majo i y o he lowe -mass and lowe -luminosi y galaxies
in hei sample. The low-mass and low-luminosi y galaxies
om he B own e al. (2019)sample ha a e no included in ou
sample a e la gely ones ha we e selec ed by ou luminosi y cu ,
bu we e oo ain o ob ain spec a wi h well-measu ed emission
line fluxes. The edshi s in ou sample a e dis ibu ed simila ly
o he o e all B own e al. (2019)sample, wi h edshi s
o z0.05.
The elescopes and ins umen s used o ob ain he spec a o
ou sample we e: (1) he Inamo i–Magellan A eal Came a and
Spec og aph (IMACS; D essle e al. 2011)on he 6.5 m
Magellan–Baade elescope; (2) he Low-Dispe sion Su ey
Spec og aph 3 (LDSS-3)on he 6.5 m Magellan Clay elescope;
(3) he Mul i-Objec Double Spec og aph (MODS; Pogge e al.
2010)on he dual 8.4 m La ge Binocula Telescope (LBT);(4) he
2
The As ophysical Jou nal, 950:108 (11pp), 2023 June 20 Holoien e al.
Mul i-Uni Spec oscopic Explo e (MUSE; Bacon e al. 2014),
loca ed a he Nasmy h B ocus o Yepun, he Ve y La ge
Telescope UT4 elescope a Ce o Pa anal Obse a o y; and (5)
he Po sdam Mul i-Ape u e Spec og aph (PMAS;Ro he al.
2005)moun ed on he 3.5 m elescope o he Cen o As onómico
Hispano Alemán a he Cala Al o Obse a o y. Wi h he
excep ion o he MUSE and PMAS spec a, hese spec a
consis ed o longsli spec a ob ained a he pa allac ic angle and
cen e ed on he hos nucleus, wi h o al in eg a ion imes ypically
be ween 1 and 4 h . We chose o cen e ou spec a on he hos
nuclei, as he majo i y o he galaxies in ou sample a e ei he oo
small o di e en ia e he loca ion o he SN om he hos nucleus
o oo di use o ob ain a high-S/N spec um a he SN loca ion.
We used IRAF o educe ou IMACS and LDSS-3 spec a
ollowing s anda d p ocedu es, including bias sub ac ion, fla -
fielding, one-dimensional spec al ex ac ion, and wa eleng h
calib a ion using a compa ison lamp spec um. The MODS
spec a we e educed using he MODS spec oscopic pipeline.
22
We flux-calib a ed ou spec a using obse a ions o spec o-
pho ome ic s anda d s a s ob ained on he same nigh s as ou
galaxy spec a.
Se en o he spec a in ou sample we e ob ained wi h
MUSE. I s modula s uc u e is composed o 24 iden ical
in eg al field uni (IFU)modules ha oge he sample, in Wide
Field Mode, a nea -con iguous 1 a cmin
2
field o iew (FOV)
wi h spaxels o 0 2×0 2, a wa eleng h co e age o 4650 Å–
9300 Å, and a mean esolu ion o R∼3000. This p oduces
∼100,000 spec a pe poin ing. These obse a ions we e
ob ained by he All-wea he MUSE Supe no a In eg al field
o Nea by Galaxies
23
(Galbany e al. 2016; L. Galbany e al.
2023, in p epa a ion)su ey. This su ey has been unning o
10 semes e s and has compiled obse a ions o mo e han 600
nea by SN hos galaxies.
One addi ional spec um (UGC 08503)was ob ained wi h
PMAS in PPak mode (Ve heijen e al. 2004; Kelz e al. 2006).
PPak consis s o a fibe bundle o 382 fibe s wi h 2 7 diame e ,
331 o which a e o de ed in a single hexagonal bundle, wi h he
emaining fibe s being used o sky measu emen s and
calib a ion pu poses. Obse a ions we e pe o med using he
V500 g a ing, which has a spec al esolu ion o ∼6Åo e he
wa eleng h ange 3750 Å–7300 Å. The final p oduc is a h ee-
dimensional da a cube wi h a 100% co e ing ac o wi hin a
hexagonal FOV o ∼1.3 a cmin
2
wi h 1″×1″pixels, which
co espond o ∼4000 spec a pe objec . This obse a ion is pa
o he PMAS/PPak In eg al field Supe no a hos s COmpila ion
(PISCO;
24
Galbany e al. 2018), a p ojec ha aimed a building
a sample o SN hos galaxies o en i onmen al s udies
(Galbany e al. 2014,2016). As o 2022 May, he PISCO
sample con ained 363 galaxies.
To ex ac he global spec a o he hos galaxies om he
MUSE and PMAS da a, we defined an ellip ical ape u e by
fi ing an ellip ical Sé sic p ofile o he galaxy ligh , using an
image ob ained by comp essing he cube in he wa eleng h
di ec ion, simula ing an image wi h a fla fil e om ∼4800 Å o
∼9300 Å. Ci cula ape u es we e placed a he posi ions o
o eg ound s a s selec ed om he Gaia Ea ly Da a Release 3
ca alog (Gaia Collabo a ion e al. 2021), and he flux wi hin he
ape u es was emo ed and in e pola ed om he nea by pixels
ou side he ape u e.
2.2. Line Measu emen s
In o de o calcula e he me allici ies and SFRs o he galaxies
in ou sample, we fi s measu ed he fluxes o he emission lines
in he spec a. To do so, we used he Py hon code PPXF
(Cappella i 2012,2017) o simul aneously fi he s ella
backg ound needed o model he e ec s o s ella abso p ion
lines and he emission line fluxes. PPXF uses he Penalized
Pixel-Fi ing me hod (Cappella i & Emsellem 2004; Cappella i
2017) o ex ac he galaxy s ella and gas kinema ics, s ella
popula ion, and gas emission lines, by fi ing a se o empla es
o an obse ed spec um. A e fi ing a s ella empla e o he
obse ed spec um, PPXF sub ac s he empla e om he
spec um and fi s Gaussian p ofiles o each o he emission
lines. Each line is fi indi idually, wi h he excep ions o he
[OIII]λ4959/5007, [OI]λ6300/6364, and [NII]λ6548/6583
double s, whe e he b igh e o he wo lines a e fi and he lines
a e assumed o ha e a 3:1 flux a io.
We ob ained line fluxes by in eg a ing he Gaussian model o
each emission componen . We calcula ed equi alen wid hs o
Hαand Hβby es ima ing he con inuum using egions nea he
lines in he obse ed spec um (p io o he PPXF empla e
sub ac ion)and di iding he measu ed line flux by he
con inuum es ima e. An example hos galaxy spec um, he
bes -fi s ella empla e, and he combined s ella empla e +
emission lines model a e shown in Figu e 2. The PPXF emission
line models a e shown in g ay.
Figu e 1. His og ams o he edshi s (le panel), s ella masses (middle panel), and luminosi ies ( igh panel) o he low-luminosi y hos galaxy sample p esen ed in
his pape (blue)and he ull SN Ia hos galaxy sample om B own e al. (2019; ed). S ella mass is shown in Sola masses and he luminosi y is ela i e o L
å
, assuming
M
24.
2
K,S
=- (Kochanek e al. 2001).
22
h p://www.as onomy.ohio-s a e.edu/MODS/So wa e/modsIDL/
23
h ps://amusing-muse.gi hub.io/
24
h ps://gi hub.com/lgalbany/pisco
3
The As ophysical Jou nal, 950:108 (11pp), 2023 June 20 Holoien e al.
Finally, we es ima ed he dus ex inc ion in each galaxy by
compa ing he Balme dec emen (Hα/Hβ) o he expec ed
alue o 2.86 o Case B ecombina ion (Os e b ock 1989).
Roughly 29% o he galaxies in ou sample ha e Balme
dec emen s consis en wi h he Case B a io wi hin 3σ.We
assume ze o ex inc ion o he h ee galaxies in ou sample wi h
Hα/Hβ<2.86. We hen calcula e E(B−V)and co ec he
flux o each spec oscopic line o ex inc ion using he same
Ca delli e al. (1989)R
V
=A(V)/E(B−V)=3.1 ex inc ion law
used in o he s udies o low-luminosi y galaxies. Ou final
ex inc ion-co ec ed line fluxes and equi alen wid hs a e
p esen ed in Table 1.
Figu e 2. The MODS/LBT da a o he galaxy 2MASX J03051061+3754003, he hos o he supe no a ASASSN-15li, and fi s om PPXF. The black cu e is he
obse ed spec um, he ed cu e is he s ella con inuum fi , and he gold cu e is he combined s ella con inuum +emission line fi . The lines included in he fi a e
ma ked and labeled in g ay. The lowe panels show zoomed-in iews o se e al fi ed lines, as well as he esidual di e ence be ween he da a and he combined model
in magen a. The labels in he uppe le co ne s gi e he lines being shown in each panel.
(The da a used o c ea e his figu e a e a ailable.)
Table 1
Emission Line Fluxes o Ou Low-L SN Ia Hos Galaxy Sample
Galaxy Name
a
Line 2MASX J03051061+3754003 AGC 331536 APMUKS(BJ)B032028.93−441621.0 CGMW 2-2125
[OII]λ3727 +3729 5748.0 ±212.4 78.63 ±6.53 LL
Hδ98.07 ±12.1 4.49 ±0.49 156.7 ±9.68 29.7 ±18.3
Hγ489.7 ±19.28 8.54 ±0.72 309.2 ±13.92 30.64 ±17.45
Hβ1263.0 ±36.57 21.65 ±1.4 714.9 ±24.89 71.91 ±30.22
[OIII]λ4959 1071.0 ±29.22 14.44 ±0.89 635.8 ±20.89 32.3 ±12.98
[OIII]λ5007 3170.0 ±85.39 43.15 ±2.62 1889.0 ±61.3 95.02 ±37.71
[OI]λ6300 124.9 ±8.1 2.27 ±0.45 24.09 ±6.8 11.46 ±7.16
[OI]λ6364 41.2 ±2.66 0.75 ±0.15 7.98 ±2.24 3.78 ±2.34
[NII]λ6548 142.5 ±3.78 2.85 ±0.19 84.94 ±3.04 17.06 ±5.27
Hα3608.0 ±71.15 61.89 ±2.75 2043.0 ±48.56 205.3 ±58.61
[NII]λ6583 425.8 ±11.24 8.52 ±0.58 253.7 ±9.03 50.82 ±15.6
[SII]λ6716 567.2 ±13.39 10.39 ±0.65 323.3 ±10.34 92.75 ±26.35
[SII]λ6731 388.0 ±10.82 9.2 ±0.62 218.9 ±8.77 21.98 ±8.77
HαEW (Å)41.07 ±0.1 19.18 ±0.13 96.76 ±0.31 11.32 ±0.35
HβEW (Å)8.51 ±0.07 4.71 ±0.08 16.74 ±0.16 2.32 ±0.27
No es. Ex inc ion-co ec ed line fluxes and equi alen wid hs o he galaxies in ou sample. The line fluxes we e calcula ed using PPXF and co ec ed o ex inc ion
using he Balme dec emen , as desc ibed in Sec ion 2.2. All fluxes a e gi en in uni s o 10
−17
e g s
−1
cm
−2
and equi alen wid hs a e gi en o Hαand Hβin Å.A
po ion o he able is shown he e o guidance ega ding i s o m and con en ; he ull able is a ailable in machine- eadable o ma in he online jou nal.
a
Fo cases whe e a galaxy has no been p e iously ca aloged by any su ey, and hus does no ha e an a chi al name o designa ion, we use “Unca alogued” o he
name and gi e he co esponding SN name in pa en heses.
(This able is a ailable in i s en i e y in machine- eadable o m.)
4
The As ophysical Jou nal, 950:108 (11pp), 2023 June 20 Holoien e al.
In Figu e 3, we show se e al line diagnos ic diag ams wi h
ou low-luminosi y hos sample compa ed o he Sloan Digi al
Sky Su ey Da a Release 8 (SDSS DR8; Eisens ein e al. 2011)
sample o galaxies. The le panel shows he Baldwin–Phillips–
Te le ich diag am (BPT diag am; Baldwin e al. 1981), he
cen e panel shows he log([SII]/Hα) e sus log([OII]/Hβ)
diag am (Veilleux & Os e b ock 1987), and he igh panel
shows he WHAN (Hαequi alen wid h e sus [NII]/Hα)
diag am (Cid Fe nandes e al. 2011). Lines di iding di e en
ypes o galaxies ( ypically s a - o ming e sus ac i e galac ic
nucleus, o AGN)a e shown in each panel and desc ibed in he
figu e cap ion. In all h ee cases, he as majo i y o he galaxies
in ou sample clea ly lie in he s a - o ming o H II egions o he
diag ams, al hough a ew all in he “Composi e” egion o he
BPT diag am o he Sey e egion o he [SII]/Hαdiag am.
Ou sample is la gely clus e ed in a egion o he BPT diag am
ha is popula ed by low-mass s a - o ming galaxies, which
ein o ces he low-mass na u e o ou sample (see Sec ion 2.3).
Gi en he s ong emission lines p esen in ou spec a and he
low-luminosi y, low-mass na u e o he sample, hei loca ions
in hese diagnos ic figu es a e unsu p ising.
2.3. Physical P ope ies
The analyses p esen ed he e p ima ily conside ou physical
p ope ies o ou galaxies: he s ella mass, he me allici y, he
SFR, and he sSFR. S ella masses o he galaxies we e
calcula ed by B own e al. (2019). They compu ed masses o
he galaxies using Fi ing and Assessmen o Syn he ic
Templa es (FAST; K iek e al. 2009) o fi spec al ene gy
dis ibu ions (SEDs) o a chi al pho ome y o he galaxies. The
a chi al pho ome y included GALEX NUV, SDSS o
Pano amic Su ey Telescope and Rapid Response Sys em
(Pan-STARRS)op ical, Two Mic on All Sky Su ey (2MASS)
JHK
S
, and Wide-field In a ed Su ey Explo e (WISE)W1 and
W2 da a, o a subse he eo when eliable magni udes we e no
a ailable o all bands. Thei fi s assumed a Ca delli e al. (1989)
ex inc ion law wi h R
V
=3.1, Galac ic ex inc ions om Schlafly
& Finkbeine (2011), and used an exponen ially declining s a
o ma ion his o y, a Salpe e (1955)ini ial mass unc ion (IMF),
and he B uzual & Cha lo (2003)s ella popula ion models o
he fi s. Due o he he e ogenous pho ome y used o he fi ,
hey assumed a minimum unce ain y o 0.1 mag o all
magni udes, in o de o a oid he fi being biased by a ificially
small unce ain ies in a gi en fil e . A compa ison o hei
esul s wi h he alues om he Max Planck Ins i u e o
As ophysics and he Johns Hopkins Uni e si y (MPA-JHU)
Galspec pipeline (Kau mann e al. 2003)indica ed ha he
masses hey de i e a e la gely consis en wi h hose om
Galspec, and we adop he B own e al. (2019)masses in ou
analyses.
One galaxy in ou sample, he unca alogued hos o
CSS141227:132741−111252, was no included in he B own
e al. (2019)analysis, as i was p e iously no de ec ed in
a chi al da a. We ob ained g izy K on magni udes o he hos
om Pan-STARRS (Chambe s e al. 2016; Flewelling e al.
2020)and in a ed W1 and W2 magni udes om he WISE
(W igh e al. 2010,2019)AllWISE ca alog and fi he SED
using FAST in he same manne as B own e al. (2019).Wefind
ha he hos has a s ella mass o ()M1.35 10
0.03
0.06 8
=´
-
+M
e
,
consis en wi h a dwa galaxy and simila o many galaxies in
ou sample. One addi ional galaxy in ou sample, GALEXASC
J134316.80−313318.2, has limi ed a chi al da a a ailable wi h
which o fi he SED, and only has an uppe limi on i s mass in
B own e al. (2019). We use he same limi he e.
T ansla ing emission line fluxes in o gas-phase me allici ies is
highly dependen on he choice o calib a ion, wi h di e en
calib a ions o en disag eeing by as much as ∼0.5 dex (e.g.,
Kewley & Ellison 2008). Fu he , me allici y calib a ions a e
only alid o specific anges o line a ios o me allici ies and/
o based on di e en es ima es o physical p ope ies ha
co ela e wi h me allici y. Finding a single me hod ha can be
used o a wide ange o me allici ies is di ficul . Empi ical
me allici y calib a ions a e gene ally p e e ed, as hey a e based
on he elec on empe a u e abundance scale, bu hey a e
ypically calcula ed based on samples ha do no co e he ull
ange o galaxy pa ame e space.
We calcula e gas-phase me allici ies o he galaxies in ou
sample using he empi ical calib a ions de i ed by Cu i e al.
Figu e 3. Emission line diagnos ic diag ams o ou sample (blue squa es). Le panel: BPT diag am showing log([OIII]/Hβ) s. log([NII]/Hα)(Baldwin e al. 1981;
Veilleux & Os e b ock 1987). The solid line shows he sepa a ion be ween AGNs (abo e)and H II/s a - o ming egions (below), based on heo e ical models (Kewley
e al. 2001), while he do ed line shows he same classifica ions based on empi ical models (Kau mann e al. 2003). Cen e panel: log([OIII]/Hβ) s. log([SII]/Hα)
diagnos ic om Veilleux & Os e b ock (1987). The solid line sepa a es AGNs om H II egions, as in he BPT diag am (Kewley e al. 2001), and he diagonal dashed
line sepa a es Sey e s (abo e)and LINERs (below; Kewley e al. 2006). Righ panel: Hαemission line equi alen wid h (EW
Hα
)compa ed o log([NII]/Hα), also
called he WHAN diag am (Cid Fe nandes e al. 2011). Lines sepa a ing s a - o ming galaxies (SF), s ong AGNs (sAGN), weak AGNs (wAGN), and passi e/“ e i ed
galaxies”(RG)a e shown (Cid Fe nandes e al. 2011). In all panels, galaxies om SDSS DR8 (Eisens ein e al. 2011)a e shown in black.
5
The As ophysical Jou nal, 950:108 (11pp), 2023 June 20 Holoien e al.

(2017). Cu i e al. (2017)calcula ed a new se o empi ical
me allici y calib a ions using a uni o m applica ion o he T
e
me hod ac oss he ull me allici y ange spanned by SDSS
galaxies. Thei calib a ions span mo e han 1 dex in me allici y,
ha e been calcula ed o se e al commonly used line a ios, and
he calib a ions o di e en line a ios a e consis en wi h one
ano he o wi hin 0.05 dex. They a e ideal o bo h ou low-
luminosi y SN hos galaxy sample and he compa ison samples
we use (see Sec ion 3below).
We use he Cu i e al. (2017)N2 me hod, based on he log
([NII]λ6583/Hα) a io, o calcula e he me allici ies p esen ed
in ou analyses. This acili a es compa ison wi h he la ges
numbe o galaxies in ou compa ison samples, many o which
do no ha e he spec oscopic co e age o use o he line a ios.
Al hough all s ong-line me hods ul ima ely ely on unde lying
co ela ions among pa ame e s, such as ioniza ion and
me allici y (e.g., Kewley & Dopi a 2002; Nagao e al. 2006),
he consis ency be ween ou hos galaxy sample and SDSS (see
Figu e 3)sugges s ha hey a e simila enough o he calib a ion
sample om Cu i e al. (2017) ha he use o hei N2
diagnos ics is eliable. Fo cases whe e he unce ain ies on he
log([NII]/Hα) a io we e la ge han he a ios hemsel es, we
ins ead calcula ed 1σuppe limi s on he line a io and hen
calcula ed 1σuppe limi s on he me allici ies. One galaxy in
ou sample, GALEXASC J005328.92−362154.1, does no
ha e a clea de ec ion o [NII]λ6583 because i is blended wi h
a e y b igh Hαline, and we exclude his galaxy om he
me allici y analysis.
The cu en SFR is ypically calcula ed using he Hαline
luminosi y. As pa o he line-measu ing p ocess, we also
measu ed he edshi s o he galaxies in ou sample, o e ified
he a chi al edshi s. Fo each galaxy, we used ou spec o-
scopic edshi o calcula e he luminosi y dis ance, and hen
calcula ed he o al es - ame Hαluminosi y om he
eddening-co ec ed Hαline flux. We con e ed his luminosi y
o an SFR using he Kennicu (1998) o mula. As Kennicu
(1998)adop ed a powe -law Salpe e (1955)IMF, we mul iplied
he esul ing SFR by 0.7 o con e om a Salpe e (1955)IMF
o a Chab ie (2003)IMF, which co ec s o he fla ening o he
IMF below 1M
e
. This is he same p ocedu e used by Hsyu e al.
(2018) o calcula e SFRs o hei low-me allici y, low-mass
galaxy sample ha we use as a compa ison sample in Sec ion 3.
A e calcula ing he SFRs o ou sample, we also calcula e he
sSFRs by di iding he SFRs by he s ella masses om he
b oadband SED fi s. Fo he case o GALEXASC J134316.80
−313318.2, wi h only an uppe limi on i s mass, we ea he
calcula ed sSFR as a lowe limi .
Though we do no examine luminosi y in de ail in ou
analyses, ou sample was selec ed based on a luminosi y
h eshold (LLlog 1.5
-), and we also epo he luminos-
i ies o ou galaxies based on 2MASS (Sk u skie e al. 2006,
2019)K
S
-band magni udes. We collec ed he K
S
-band
magni udes o he galaxies in ou sample om he ASAS-SN
B igh Supe no a Ca alogs (Holoien e al. 2017a,2017c,
2017b) om which ou sample was d awn. As he K
S
-band
magni ude has a well-defined luminosi y unc ion (Kochanek
e al. 2001), i p o ides a na u al es ima e o he s ella
luminosi ies o he galaxies in ou sample. In he ASAS-SN
ca alogs, he au ho s ob ained he 2MASS magni udes om he
2MASS Ex ended Sou ce Ca alog when a ailable, and om he
2MASS Poin Sou ce Ca alog when he galaxies we e no
de ec ed in he Ex ended Sou ce Ca alog. Fo galaxies no
de ec ed in 2MASS bu de ec ed in WISE W1 da a, hey
es ima ed he K
S
-band magni ude by sub ac ing he a e age
K
s
−W1 o se o −0.51 mag calcula ed om all galaxies
de ec ed in bo h fil e s. Finally, o galaxies no de ec ed by
ei he 2MASS o WISE, hey assumed an uppe limi o
K
s
>15.6, equal o he ain es de ec ed galaxy in hei sample.
A e collec ing he K
S
appa en magni udes om he ASAS-SN
ca alogs, we hen con e ed o absolu e magni udes using he
dis ance moduli calcula ed om he galaxies’spec oscopic
edshi s.
The coo dina es, edshi s, dis ances, masses, me allici ies,
SFRs, sSFRs, and absolu e K
S
-band magni udes o he galaxies
in ou sample a e p esen ed in Table 2. Redshi s ha had no
been p e iously measu ed o ha di e om p e iously
epo ed measu emen s a e no ed wi h an as e isk.
As ou sample la gely consis s o longsli spec a cen e ed on
he galaxy nuclei, he e is a possibili y ha he p ope ies we
de i e om hese spec a a e no uly “global.”Because o his,
we pe o med some checks o e i y ha he line fluxes and
galaxy p ope ies we de i e can be obus ly compa ed o o he
galaxy samples. Fi s , looking a he acquisi ion images o ou
spec a, he majo i y o ou sample consis s o small galaxies
whose ligh is mos ly con ained wi hin he sli . Thus, only o a
hand ul o cases is he e a chance o significan sli losses.
Fu he , a hand ul o ou sample we e obse ed mul iple imes,
ei he wi h di e en longsli o ien a ions o wi h bo h MUSE
and one o ou longsli ins umen s. We find ha he p ope ies
we de i e o he galaxies wi h mul iple obse a ions a e
consis en be ween obse a ions, implying ha we a e able o
measu e galaxy p ope ies obus ly wi h ou longsli spec a.
We also compa ed ou de i ed SFRs o he SFRs de i ed by
B own e al. (2019) om hei pho ome ic SED fi s, finding ha
he SFRs we de i e om he Hαluminosi ies a e consis en
wi h hei SFRs. Finally, we ake s eps o ensu e ha ou
compa ison samples a e cap u ing a simila ac ion o hos ligh
as ou longsli spec a, so ha hey will be di ec ly compa able
o ou sample (see Sec ion 3).
3. Analysis and Compa ison o O he Galaxy Samples
To de e mine how ou SN hos galaxies compa e o gene al
galaxies, we compa e ou sample o se e al samples om
li e a u e. Ou p ima y compa ison sample is he SDSS DR8
sample (Eisens ein e al. 2011), o which line flux
measu emen s and galaxy p ope y measu emen s a e a ailable
in he MPA-JHU alue-added ca alogs. Because he SDSS
ca alog alues a e based on spec a aken wi h fibe s o 2″–3″
diame e , hei galaxy p ope ies a e no uly “global”
p ope ies, as any ligh ou side o he fibe wid h would no
be included. To make hei sample mo e di ec ly compa able o
ou s, we used only hose SDSS galaxies wi h edshi s o
z<0.05, he same edshi ange o ou sample, so ha he a ea
co e ed by hei fibe s would be oughly compa able o he a ea
co e ed by he longsli s we used o ou spec a. We also only
include galaxies wi h ()
MMlog 7
, as below his alue he
line fluxes and de i ed me allici ies a e no eliable. These
edshi and mass cu s educe he SDSS sample om 643,727 o
256,529 galaxies.
As he SDSS sample is p ima ily concen a ed owa d highe
masses and luminosi ies han ou low-luminosi y sample, we
also selec ed wo low-luminosi y samples o galaxies o
compa ison. The fi s (Be g e al. 2012; he ea e , B12)consis s
o longsli spec oscopic obse a ions o H II egions om 42
6
The As ophysical Jou nal, 950:108 (11pp), 2023 June 20 Holoien e al.
low-luminosi y galaxies in he Spi ze Local Volume Legacy
(LVL)su ey. The second (Hsyu e al. 2018; he ea e , H18)
consis s o longsli spec oscopic obse a ions o 45 low-
me allici y blue compac dwa galaxies selec ed om SDSS
DR12 (Alam e al. 2015). Al hough he la e sample was
selec ed o low me allici y a he han luminosi y, hese
sys ems a e also low-mass and low-luminosi y. As bo h samples
use longsli spec a wi h simila sli wid hs as ou da a, we do
no pe o m any addi ional co ec ions o make hem
compa able o ou sample.
Fo he SDSS sample, we used he s ella masses and SFRs
om he MPA-JHU ca alog and calcula ed he sSFRs using
hose. As he MPA-JHU ca alogs used a K oupa (2001)IMF o
calcula e he masses and SFRs, we con e ed hei measu e-
men s o a Salpe e (1955)IMF by mul iplying hem by a ac o
o 1.5 (B inchmann e al. 2004), hen con e ed he SFRs o a
Chab ie (2003)IMF by mul iplying by 0.7, so ha hey would
be di ec ly compa able o he o he samples. Though he MPA-
JHU sample is he la ges o he ou samples we compa e, we
elec ed o con e all ou samples o a Chab ie (2003)IMF, as
his has been p o en o be accu a e o low-mass, low-
luminosi y samples like ou s (e.g., ha o H18). I is also only
a mino co ec ion, as he K oupa (2001)and Chab ie (2003)
IMFs a e qui e simila . Fo he B12 sample, we used he masses
om hei pape . As hei pape p o ided spec a o H II egions,
a he han o he galaxies as a whole, we we e unable o use he
epo ed Hαfluxes o calcula e he Hαluminosi ies and SFRs
o he galaxies. Ins ead, we use he Hαluminosi ies o he
LVL galaxies om Kennicu & Lee (2008) o calcula e he
SFRs and sSFRs o he B12 sample.
25
Fo galaxies in he B12
sample wi h mul iple spec a o H II egions, we use he same
SFRs and masses and calcula e he me allici ies o each H II
egion sepa a ely. Kennicu & Lee (2008)do no gi e
unce ain ies o he Hαluminosi ies in hei sample, and
ins ead gi e a ange o ±0.07–0.15 dex, based on he ypical
unce ain ies on he dis ances o he galaxies. We assume an
unce ain y o 0.15 dex on L
Hα
, he uppe end o hei specified
ange, when calcula ing SFRs o galaxies in he B12 sample.
Finally, o he H18 sample, we ob ained masses and SFRs om
hei pape .
Fo all h ee samples, we used he [NII]λ6583 and Hαfluxes
o calcula e he Cu i N2 me allici ies, as we did o ou sample.
We calcula ed uppe limi s on he me allici ies when he
[NII]λ6583 and Hαlines we e no obus ly de ec ed.
Figu e 4shows he dis ibu ion o ou sample and he
compa ison samples in s ella mass and me allici y. As has been
ound o SN Ia hos galaxies in he pas (e.g., Child ess e al.
2013), ou galaxies do no clea ly s and ou om he o he
galaxy samples. They la gely all on he low-M, low-me allici y
ail o he dis ibu ion o he SDSS sample and o e lap wi h he
highe -me allici y galaxies om he B12 sample. The H18
sample is la gely lowe in mass and me allici y han ou sample,
bu his is unsu p ising, gi en ha i was specifically selec ed o
be low me allici y.
Fi e o he six lowes -mass galaxies in ou sample ha e
me allici ies ha appea high o hei masses, and we flagged
hese as po en ial ou lie s. These galaxies a e: ESO 357-G005
(ASASSN-15pz), GALEXASC J063224.91−713403.9 (OGLE16dha),
GALEXASC J010647.95−465904.1 (ASASSN-14lw),UGCA
430 (ASASSN-16j ), and he unca alogued hos o ASASSN-
15 y. We highligh hese fi e galaxies using pu ple ou lines in
Figu e 4.
To es whe he hese galaxies uly ha e abno mally high
me allici ies when compa ed o he es o ou sample and he
compa ison samples, we fi all o he low-L samples wi h a
linea equa ion o he o m
() (( ) ) ()

aMM b12 log O H log , 1
M
m+= -+
whe e ais he slope, bis he in e cep , and μ
M
is he mean log
(M
å
)o he sample being fi . We pi o he ela ions on he mean
in o de o make he unce ain ies on he aand bpa ame e s
Table 2
Physical P ope ies o Ou Low-L SN Ia Hos Galaxy Sample
Dis ance (
)
Mlog (
)
log SFR (
)
log sSFR
Galaxy Name
a
SN Name Redshi
b
(Mpc)(M
e
)(
)1
2logOH+
c
M
e
y
−1
Gy
−1
M
KS
d
2MASX J03051061 ASASSN-15 i 0.0172 75.1 8.72 0.04
0.0
4
-
+8.45 0.01
0.01
-
+0.87 0.01
0.01
--
+0.59 0.05
0.05
--
+−18.18 ±0.20
AGC 331536 ASASSN-16ke 0.028 123.0 8.60 0.11
0.2
8
-
+8.49 0.02
0.02
-
+2.21 0.02
0.02
--
+1.81 0.30
0.13
--
+−17.26 ±0.11
APMUKS(BJ)B032028.93 ASASSN-16dx 0.0295 130.0 8.05 0.17
0.60
-
+8.47 0.01
0.01
-
+0.64 0.01
0.01
--
+0.310 0.61
0.1
8
-
+−18.37 ±0.20
CGMW 2-2125 ASASSN-16jq 0.018 78.6
9
.10
0.16
0.36
-
+
8.62 0.10
0.12
-
+2.08 0.15
0.11
--
+2.18 0.51
0.27
--
+>−18.88
ESO 113-G047 ASASSN-14me 0.018 78.6 8.46 1.13
0.62
-
+8.35 0.02
0.02
-
+0.54 0.01
0.01
--
+0.00 0.63
1.1
4
--
+−17.19 ±0.11
ESO 357-G005 ASASSN-15pz 0.0149 64.9
7
.28 0.34
0.8
6
-
+8.65 0.10
0.13
-
+2.34 0.1
4
0.11
--
+0.62 1.00
0.45
--
+−16.67 ±0.11
ESO 466-G032 2016ekg 0.0171 74.6 8.79 0.05
0.03
-
+8.56 0.01
0.01
-
+2.15 0.01
0.01
--
+1.94 0.04
0.0
6
--
+−18.16 ±0.20
ESO 509-IG064 ASASSN-16hp 0.008663 37.6 8.57 0.05
0.01
-
+8.46 0.00
0.0
0
-
+1.49 0.01
0.01
--
+1.06 0.02
0.0
6
--
+−17.88 ±0.10
GALEXASC J000802.78 ASASSN-15 q 0.0236 104.0 8.43 0.67
0.70
-
+8.47 0.04
0.0
4
-
+1.29 0.04
0.0
4
--
+0.72 0.7
4
0.71
--
+−17.38 ±0.11
No es. Physical pa ame e s o he galaxies in ou sample. Desc ip ions o how each p ope y was calcula ed a e gi en in Sec ion 2.3. A po ion o he able is shown
he e o guidance ega ding i s o m and con en ; he ull able is a ailable in machine- eadable o ma in he online jou nal.
a
Fo cases whe e a galaxy has no been p e iously ca aloged by any su ey, and hus does no ha e an a chi al name o designa ion, we use “Unca alogued” o he
name. Some galaxy names a e abb e ia ed he e o p e en he wid h o he able om ex ending beyond he page, bu ull names a e gi en in he e sion o he able
a ailable in he online jou nal.
b
Redshi s ha had no been p e iously measu ed o ha di e subs an ially om a chi al measu emen s a e deno ed wi h an as e isk.
c
Me allici ies a e calcula ed using he N2 me hod o Cu i e al. (2017).
d
K
S
-band magni udes a e aken om he 2MASS ca alogs when a ailable, o calcula ed om he WISE W1-band magni udes when no . I he galaxy is no de ec ed in
ei he ca alog, we assume an uppe limi o m15.6
KS>, as desc ibed in he ex .
(This able is a ailable in i s en i e y in machine- eadable o m.)
25
Fou o he galaxies in he B12 sample do no ha e Hαluminosi ies in
Kennicu & Lee (2008), and we exclude hese om ou analyses o SFR
and sSFR.
7
The As ophysical Jou nal, 950:108 (11pp), 2023 June 20 Holoien e al.
essen ially unco ela ed. To obus ly measu e he fi and
es ima e he unce ain ies on he aand bpa ame e s, we use
boo s ap esampling wi h 15,000 i e a ions. We find (a,b)
us
=
(
)0.60 , 8.34
0.15
0.37 0.13
0.05
-
+
-
+ o ou sample, whe e he bes -fi alue is
he median o ou boo s apped alues and he e o s a e 1σ
unce ain ies. Fo he B12,H18, and SDSS samples, we find
(a,b)
B12
=(
)
0.36 , 8.21
0.06
0.09 0.04
0.04
-
+
-
+,(a,b)
H18
=(
)
0.38 , 7.88
0.09
0.15 0.07
0.05
-
+
-
+,
and (a,b)
SDSS
=
(
)0.39 , 8.53
0.02
0.01 0.01
0.01
-
+
-
+ espec i ely. Fo he SDSS
fi , we only include hose galaxies wi h ()
MMlog 9.7
, o
exclude he galaxies wi h masses abo e he scale whe e he slope o
he ela ion becomes shallowe .
In Figu e 5, we show ou sample as well as he bes -fi lines
and 1σunce ain ies o all ou galaxy samples. All h ee fi s
a e gene ally qui e consis en h ough he mass ange shown,
pa icula ly hose o he B12 and H18 samples. We find ha o
he fi e poin s we iden ified as ha ing po en ially high
me allici ies, only wo, UGCA 430 and he hos o ASASSN-
15 y, a e ou lie s om all ou fi s a he 3σle el. We highligh
hese wo poin s in magen a in Figu e 5. Wi h only wo ue
ou lie s, we hus conclude ha he e is no significan e idence
om ou sample ha he lowes -mass SN Ia hos galaxies a e
mo e me al- ich han ypical low-mass galaxies.
Howe e , while no indi idually significan , he e seem o be
an excess o galaxies ha a e me al- ich o hei masses, wi h
10 o he 14 lowes -mass galaxies lying ∼1σabo e all bu he
H18 end line. Fu he , none o ou galaxies ha e low
me allici ies o hei masses. Some o his is in pa due o
ou sample selec ion me hod, emo ing highe -mass galaxies,
a he han a lack o hese ypes o galaxies in gene al. Howe e ,
he e is weak e idence ha low-mass SN Ia hos galaxies may
be mo e en iched han hei non-SN-hos coun e pa s.
We also looked a o he p ope ies o ou sample and he
compa ison samples o examine whe he he e a e any o he
cha ac e is ics o which he wo 3σou lie s a e unique, o
whe he ou sample s ands ou . Figu e 6shows he s ella
masses o ou sample and he compa ison samples compa ed o
hei cu en SFRs. The magen a line in he figu e co esponds
o log(sSFR)<−11, and is he di ision used by B own e al.
(2019) o sepa a e ac i ely s a - o ming and passi e galaxies.
As expec ed, based on hei loca ions in he diagnos ic diag ams
o Figu e 3, he majo i y o ou galaxies lie abo e his di iding
line, implying ha hey a e ac i ely s a - o ming. The six
galaxies below he line a e all e y close o he di iding line, and
o hese, only ou a e inconsis en wi h being abo e he line,
gi en he unce ain ies on hei masses and SFRs. Ou sample
does no clea ly s and ou om any o ou compa ison samples,
and is qui e simila o he B12 sample, in pa icula . The wo
galaxies no ed as ha ing high me allici ies o hei masses a e
again highligh ed in magen a in he figu e. While hey do ha e
some o he lowe SFRs o he galaxies in ou sample, hey do
no s and ou om he o he galaxies. We conclude ha he e is
no hing a ypical abou he SFRs o ou sample, gi en hei
masses.
In Figu e 7, we show he SFRs and me allici ies o ou
sample. Ou galaxies end o ha e highe me allici ies han he
galaxies wi h simila SFRs in ou low-L compa ison samples,
bu a e gene ally consis en wi h he ou e edge o he SDSS
sample. The e is li le o e lap be ween ou sample and he H18
sample, while he B12 sample is ai ly e enly sp ead h oughou
he egion spanned by ou sample and he H18 sample. The e is
no clea end in me allici y wi h SFR o he h ee low-L
samples shown he e, wi h he me allici y sp ead o each sample
being ai ly fla o e a wide ange o SFRs. The wo high-
me allici y galaxies no ed in magen a do no s and ou om he
es o he galaxies in ou sample in he SFR–me allici y plane.
Figu e 4. S ella masses and Cu i N2 me allici ies o ou SN Ia hos galaxy
sample (blue squa es)compa ed o he low-L galaxy samples o B12 (yellow
ci cles)and H18 ( ed s a s). SDSS DR8 galaxies a e shown in black. 1σuppe
limi s in me allici y a e shown as downwa d- acing iangles and uppe limi s in
mass a e shown as le wa d- acing iangles. The fi e galaxies highligh ed wi h
a pu ple ou line indica e he fi e e y-low-mass galaxies we iden ified as
po en ial ou lie s, wi h pa icula ly high me allici ies o hei masses. The
ho izon al dashed line indica es Sola me allici y, Z
e
=8.69 (Asplund
e al. 2009).
Figu e 5. S ella masses and Cu i N2 me allici ies o ou SN Ia hos galaxy
sample (blue squa es)compa ed o linea M–Zfi s o ou sample (na y), he B12
sample (yellow), he H18 sample ( ed), and he SDSS sample (g een). The
shaded egions in ma ching colo s show he 1σ ange o each fi . No e he
change in scales compa ed o Figu e 4, which we ha e adjus ed o mo e clea ly
ocus on ou sample. The wo da a poin s highligh ed in magen a a e 3σou lie s
om all ou M–Zfi s.
8
The As ophysical Jou nal, 950:108 (11pp), 2023 June 20 Holoien e al.
In Figu e 8, we examine he sSFRs o ou sample and
compa ison samples compa ed o hei me allici ies. We again
see ha ou sample is highe in me allici y compa ed o he o he
low-L samples, wi h e en less o e lap be ween ou sample and
he B12 and H18 samples han in he space o SFR and
me allici y. Ou sample is again gene ally consis en wi h he
SDSS DR8 sample, howe e . We again highligh he wo
galaxies iden ified as ha ing high me allici ies o hei masses,
and no e ha hey do no seem o ha e a ypical me allici ies,
gi en hei sSFRs, wi h one alling in he a ea o he figu e mos
densely popula ed by SDSS galaxies. Whe e ou galaxies show
no ob ious end in me allici y wi h inc easing sSFR, as was he
case wi h SFR, his does no appea o be ue o he o he low-
L samples. The B12 sample has a clea end, wi h he
me allici y dec easing as sSFR inc eases. While he H18 sample
does no ha e as clea a end o e all, we no e ha he highes -
me allici y galaxies in he H18 sample end o ha e highe
sSFRs.
Fo bo h SFR and sSFR, ou sample does no appea o be
pa icula ly me al- ich o me al-poo compa ed o he gene al
popula ion o galaxies om SDSS. In compa ison o simila
low-L samples in B12 and H18, howe e , ou sample is mo e
en iched o a gi en SFR/sSFR. Nei he SFR no sSFR appea
o ha e a clea co ela ion wi h me allici y in ou sample, despi e
he e being a end wi h mass.
4. Discussion
Ou spec oscopic examina ion o 44 low-luminosi y hos
galaxies o SNe Ia indica es ha his popula ion o galaxies is
simila o ypical galaxies in me allici y, SFR, sSFR, and s ella
mass. In pa icula , he SFRs and sSFRs o ou sample appea o
be qui e no mal, gi en he galaxies’masses and me allici ies.
These esul s suppo he conclusions o p e ious examina ions
o SN Ia hos galaxies (e.g., Child ess e al. 2013), which ha e
ound ha SN Ia hos s gene ally ha e me allici es simila o
galaxies o he same masses and SFRs.
While 10 o he 14 leas massi e galaxies in ou sample lie
∼1σabo e he mass–me allici y ela ions defined by ou
compa ison galaxy samples (which a e gene ally consis en
wi h one ano he , and wi h he M–Z ela ion defined by ou
en i e sample),wefind ha only wo o hese a e inconsis en
Figu e 6. The s ella masses and SFRs o ou sample compa ed o ou
compa ison samples. The colo s and symbols ma ch hose o Figu e 4, wi h he
wo poin s highligh ed wi h magen a ou lines indica ing he wo galaxies wi h
no ably high me allici ies o hei masses. The magen a dashed line shows he
di ision be ween ac i ely s a - o ming galaxies and passi e galaxies, as defined
in B own e al. (2019), co esponding o log(sSFR)<−11.
Figu e 7. The SFRs and Cu i N2 me allici ies o ou sample compa ed o ou
galaxy compa ison samples. The colo s and symbols ma ch hose o Figu e 4,
wi h he wo poin s highligh ed wi h magen a ou lines indica ing he wo
galaxies wi h no ably high me allici ies o hei masses. 1σuppe limi s in
me allici y a e shown as downwa d- acing iangles.
Figu e 8. The sSFRs and Cu i N2 me allici ies o ou sample compa ed o he
compa ison samples. The colo s and symbols ma ch hose o Figu e 4, wi h he
wo poin s highligh ed wi h magen a ou lines indica ing he wo galaxies wi h
no ably high me allici ies o hei masses. 1σuppe limi s in me allici y a e
shown as downwa d- acing iangles and lowe limi s in sSFR a e shown as
igh - acing iangles.
9
The As ophysical Jou nal, 950:108 (11pp), 2023 June 20 Holoien e al.