SUSHIES Giorgos Leloudas Weizmann Institute of Science & Dark Cosmology Centre

The people behind Ricardo Amorin Joe Anderson Franz Bauer Lise Christensen Javier Gorosabel Jens Hjorth Andrea Mehner Daniele Malesani Antonio de Ugarte Postigo Christina Thoene Craig Wheeler + more Steve Schulze Thomas Kruehler

Outline of the talk No introduction ! SUSHIES I – Leloudas et al. 2015, MNRAS, 449, 917 – Focus on spectroscopic properties SUSHIES II – Schulze et al (in prep.) – Photometry and SED properties Discussion – Is there a driving factor? – Can we disentangle at all ? What next?

SUSHIES I – results

Low MEASURED metallicities Median 0.27 Z  (M91); range: 0.14 – 0.71 Z  A few EMP (3 below 0.07 Z  ) galaxies (Direct T e ) No statistically significant difference with GRBs SLSNe II are more metal-rich (0.4 – 1.0 Z  ; p = 0.006)

However, the most striking is … H-poor hosts have VERY strong emission lines 50% are EELGs (EW > 100 Å in O III) Chance coincidence is (zCOSMOS)

Another way to say this:

High specific star formation rate See also SUSHIES II

SUSHIES I conclusions H-poor SLSNe and SLSNe IIn found in different environments – SLSN IIn progenitors are different (or a mixed bag) H-poor SLSNe show a preference for young starbursts (even more so than GRBs) Absolute ages are hard to measure but we can use GRBs as relative comparison We suggest SLSNe represent the first explosions The presence of very massive stars is supported by the hard ionization field

PTF12dam An EELG at z = Very young stellar population by a number of diagnostics. Down to 3 Myr, corresponding to > 60 M  (or even 120 M  ) Thoene et al. 2015

SUSHIES II 67 galaxies 51 H-poor, 16 H-rich z evolution (for the first time) Slow (R) and Fast (I) II and IIn Our data + archives + literature Neill et al. 2011; Lunnan et al. 2014, 2015; Vreeswijk et al. 2014; Angus et al. 2016; Perley et al. 2016; Chen et al many indiv. object papers

Brightness and color Comp. with UltraVISTA H-poor are faint – ~0.04 L * at z < 0.5 H-rich are diverse – Note II vs IIn H-poor are blue – -0.1 mag at z<0.5 – +0.5 mag for H-rich Evolution above z > 0.7 – Survey bias or real ? Angus et al. 2016

Masses and SFRs

Specific SFR Masses increase with z But they remain low in comparison to UltraVISTA sSFR are always high

Quantifying the metallicity bias Normalise stellar mass function with SF Relative contribution of mass bins in SF (z < 1) Fits well CC SNe To fit SLSNe assume an efficiency factor ρ(M * ) M – Z relation to map Z Production efficiency drops sharply at 0.4 Z  GRB 0.3 dex weaker

DISCUSSION Is there one driving factor? Is it metallicity or young age (starburst/high sSFR)? Is it possible to disentangle at all? Metallicity could be in compliance with the magnetar model Alternatively, it could mean that we understand very little of stellar evolution (and mass loss?) in young starburst (and metal- poor) environments

Starburst as a side effect of the metallicity dependence “Several SLSN-I hosts are undergoing vigorous starbursts, but this may simply be a side effect of metallicity dependence: dwarf galaxies tend to have bursty star-formation histories” Perley et al “We also confirm that high sSFR is a feature of SLSN host galaxies but interpret this as simply a consequence of the anti-correlation between gas- phase metallicity and sSFR” Chen et al. 2016

Starburst cannot be a coincidence Exactly because dwarfs have bursty SFH, it is unlikely to catch them during starburst Cycles of 1-2 Gyr. Emission lines < 100 Myr Lee et al : 6% of dwarfs are starbursts – Using 11HUGS ! – Using definition of starburst > 100 Å ! Probability of getting 50% EELGs is < 10 -6

Conclusion Either: the low metallicity is a side effect of the young environments (reversible argument!) Or: these two effects are intimately connected In any case: H-poor SLSN hosts are found in young and little enriched environments (more so than GRBs) Points to unknown stellar evolution in these extreme environments

PS1-12zn z = r‘=24.1 [O III ]λ5007Hα What is next ? PS1-12bmy z = r‘=25.5 PS1-11bdn z = i‘=25.4 Spectra further and deeper (z = 2.2)

Thank you !