Seminar 2020/11/05

Speaker: Dr. Daichi Kashino (Nagoya University, Japan)

Title：The 2175 Å dust feature in star-forming galaxies at 1.3≤z≤1.8: the dependence on stellar mass and specific star formation rate

Date/Time : Nov. 05, 2020 (Thu.) 16:30-18:00

Place：ES604

Abstract:

This talk is based on arXiv:2009.13582. We present spectroscopic measurements of the broad 2175Å absorption feature in 505 star-forming "Main Sequence" galaxies at 1.3≤z≤1.8 using individual and stacked spectra from the zCOSMOS-deep survey. Significant 2175 Å excess absorption of moderate strength are measured, which is well described by a Drude profile. The bump amplitude expressed in units of k(λ)=A(λ)/E(B−V), relative to the featureless Calzetti et al. (2000) law, has a range B_k~0.3--0.8. We found that the bump amplitude decreases with the specific SFR while it increases moderately with the stellar mass. From comparisons with local "starburst" galaxies that presents very weak or no bump and a simple toy model of star formation activity, we argue that it is the change in SFR over the last ~1Gyr that determines the bump strength through the destruction of small carbonaceous grains by supernovae and intense radiation fields couple with the time delay of ~1 Gyr in the appearance of carbon-rich AGB stars.

Presentation: slides (PDF)

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