Characterizing Supernova Progenitors via the Metallicities of their Host Galaxies, from Poor Dwarfs to Rich Spirals

We investigate how the different types of supernovae are relatively affected by the metallicity of their host galaxy. We match the SAI Supernova Catalog to the SDSS-DR4 catalog of star-forming galaxies with measured metallicities. These supernova host galaxies span a range of oxygen abundance from 12 + log(O/H) = 7.9 to 9.3 (~ 0.1 to 2.7 solar) and a range in absolute magnitude from MB = -15.2 to -22.2. To reduce the various observational biases, we select a subsample of well-characterized supernovae in the redshift range from 0.01 to 0.04, which leaves us with 58 SN II, 19 Ib/c, and 38 Ia. We find strong evidence that SN Ib/c are occurring in higher-metallicity host galaxies than SN II, while we see no effect for SN Ia relative to SN II. We note some extreme and interesting supernova-host pairs, including the metal-poor (~ 1/4 solar) host of the recent SN Ia 2007bk, where the supernova was found well outside of this dwarf galaxy. To extend the luminosity range of supernova hosts to even fainter galaxies, we also match all the historical supernovae with z < 0.3 to the SDSS-DR6 sky images, resulting in 1225 matches. This allows us to identify some even more extreme cases, such as the recent SN Ic 2007bg, where the likely host of this hypernova-like event has an absolute magnitude MB ~ -12, making it one of the least-luminous supernova hosts ever observed. This low-luminosity host is certain to be very metal poor (~ 1/20 solar), and therefore this supernova is an excellent candidate for association with an off-axis GRB. The two catalogs that we have constructed are available online and will be updated regularly. Finally, we discuss various implications of our findings for understanding supernova progenitors and their host galaxies.Comment: ApJ accepted, 26 pages, 5 figures, 1 table. Updated catalogs are available at http://www.astronomy.ohio-state.edu/~prieto/snhosts

A new Cepheid distance to the maser-host galaxy NGC 4258 and its implications for the Hubble Constant

We present initial results from a time-series BVI survey of two fields in NGC 4258 using the Advanced Camera for Surveys onboard the Hubble Space Telescope. This galaxy was selected because of its accurate maser-based distance, which is anticipated to have a total uncertainty of ~3%. The goal of the HST observations is to provide an absolute calibration of the Cepheid Distance Scale and to measure its dependence on chemical abundance (the so-called "metallicity effect"). We carried out observations of two fields at different galactocentric distances with a mean abundance difference of 0.5 dex. We discovered a total of 281 Cepheids with periods ranging from 4 to 45 days (the duration of our observing window). We determine a Cepheid distance modulus for NGC 4258 (relative to the LMC) of 10.88 +- 0.04 (random) +- 0.05 (systematic) mag. Given the published maser distance to the galaxy, this implies \mu (LMC)=18.41 +- 0.10 (r) +- 0.13 (s) mag or D(LMC)= 48.1 +- 2.3 (r) +- 2.9 (s) kpc. We measure a metallicity effect of \gamma=-0.29 +- 0.09 (r) +- 0.05 (s) mag/dex. We see no evidence for a variation in the slope of the Period-Luminosity relation as a function of abundance. We estimate a Hubble Constant of H_0= 74 +- 3 (r) +- 6 (s) km/s Mpc using a recent sample of 4 well-observed type Ia SNe and our new calibration of the Cepheid Distance Scale. It may soon be possible to measure the value of H_0 with a total uncertainty of 5%, with consequent improvement in the determination of the equation of state of dark energy.Comment: 39 pages, 24 figures. Accepted for publication in the Astrophysical Journal. Full-resolution version available in PS and PDF formats at http://www.noao.edu/staff/lmacri/0608211-full.ps.gz and http://www.noao.edu/staff/lmacri/0608211-full.pd

Thermo-ecological cost (TEC) evaluation of metallurgical processes

Metallurgy represents a complex production system of fuel and mineral non-renewable resources transformation. The effectiveness of resource management in metallurgical chains depends on the applied ore grade and on the irreversibility of components of the system. TEC can be applied to measure the influence of metallurgy on the depletion of natural resources. The paper discusses the possibility of application of TEC in metallurgy and presents illustrative example concerning blast-furnace process

Optical observations of the luminous Type IIn Supernova 2010jl for over 900 days

The luminous Type IIn Supernova (SN) 2010jl shows strong evidence for the interaction of the SN ejecta with dense circumstellar material (CSM). We present observations of SN 2010jl for $t \sim 900$ d after its earliest detection, including a sequence of optical spectra ranging from $t = 55$ to $909$ d. We also supplement our late time spectra and the photometric measurements in the literature with an additional epoch of new, late time $BVRI$ photometry. Combining available photometric and spectroscopic data, we derive a semi-bolometric optical light curve and calculate a total radiated energy in the optical for SN 2010jl of $\sim 3.5\times10^{50}$ erg. We also examine the evolution of the H$\alpha$ emission line profile in detail and find evidence for asymmetry in the profile for $t \gtrsim 775$ d that is not easily explained by any of the proposed scenarios for this fascinating event. Finally, we discuss the interpretations from the literature of the optical and near-infrared light curves, and propose that the most likely explanation of their evolution is the formation of new dust in the dense, pre-existing CSM wind after $\sim 300$ d.Comment: 14 pages, 10 figures, 5 tables. Full version of Table 3 is included as an ancillary fil