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Register a new userImaging and Demography of the Host Galaxies of High-Redshift Type Ia Supernovae
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Benjamin F. Williams
Publication date
2003
fields
Physics
and research's language is
English
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We present the results of a study of the host galaxies of high redshift Type Ia supernovae (SNe Ia). We provide a catalog of 18 hosts of SNe Ia observed with the Hubble Space Telescope (HST) by the High-z Supernova Search Team (HZT), including images, scale-lengths, measurements of integrated (Hubble equivalent) BVRIZ photometry in bands where the galaxies are brighter than m ~ 25 mag, and galactocentric distances of the supernovae. We compare the residuals of SN Ia distance measurements from cosmological fits to measurable properties of the supernova host galaxies that might be expected to correlate with variable properties of the progenitor population, such as host galaxy color and position of the supernova. We find mostly null results; the current data are generally consistent with no correlations of the distance residuals with host galaxy properties in the redshift range 0.42 < z < 1.06. Although a subsample of SN hosts shows a formally significant (3-sigma) correlation between apparent V-R host color and distance residuals, the correlation is not consistent with the null results from other host colors probed by our largest samples. There is also evidence for the same correlations between SN Ia properties and host type at low redshift and high redshift. These similarities support the current practice of extrapolating properties of the nearby population to high redshifts pending more robust detections of any correlations between distance residuals from cosmological fits and host properties.
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We compare the host galaxies of 902 supernovae, including SNe Ia, SNe II and SNe Ibc, which are selected by cross-matching the Asiago Supernova Catalog with the SDSS Data Release 7. We further selected 213 galaxies by requiring the light fraction of spectral observations $>$15%, which could represent well the global properties of the galaxies. Among them, 135 galaxies appear on the Baldwin-Phillips-Terlevich diagram, which allows us to compare the hosts in terms of star-forming, AGNs (including composites, LINERs and Seyfert 2s) and Absorp (their related emission-lines are weak or non-existence) galaxies. The diagrams related to parameters D$_n$(4000), H$delta_A$, stellar masses, SFRs and specific SFRs for the SNe hosts show that almost all SNe II and most of SNe Ibc occur in SF galaxies, which have a wide range of stellar mass and low D$_n$(4000). The SNe Ia hosts as SF galaxies follow similar trends. A significant fraction of SNe Ia occurs in AGNs and Absorp galaxies, which are massive and have high D$_n$(4000). The stellar population analysis from spectral synthesis fitting shows that the hosts of SNe II have a younger stellar population than hosts of SNe Ia. These results are compared with those of the 689 comparison galaxies where the SDSS fiber captures less than 15% of the total light. These comparison galaxies appear biased towards higher 12+log(O/H) ($sim$0.1dex) at a given stellar mass. Therefore, we believe the aperture effect should be kept in mind when the properties of the hosts for different types of SNe are discussed.
We present photometric and spectroscopic observations of galaxies hosting Type Ia supernovae (SNe Ia) observed by the Nearby Supernova Factory (SNfactory). Combining GALEX UV data with optical and near infrared photometry, we employ stellar population synthesis techniques to measure SN Ia host galaxy stellar masses, star-formation rates (SFRs), and reddening due to dust. We reinforce the key role of GALEX UV data in deriving accurate estimates of galaxy SFRs and dust extinction. Optical spectra of SN Ia host galaxies are fitted simultaneously for their stellar continua and emission lines fluxes, from which we derive high precision redshifts, gas-phase metallicities, and Halpha-based SFRs. With these data we show that SN Ia host galaxies present tight agreement with the fiducial galaxy mass-metallicity relation from SDSS for stellar masses log(M_*/M_Sun)>8.5 where the relation is well-defined. The star-formation activity of SN Ia host galaxies is consistent with a sample of comparable SDSS field galaxies, though this comparison is limited by systematic uncertainties in SFR measurements. Our analysis indicates that SN Ia host galaxies are, on average, typical representatives of normal field galaxies.
We present an analysis of the light curve (LC) decline rates $(Delta m_{15})$ of 407 normal and peculiar supernovae (SNe) Ia and global parameters of their host galaxies. As previously known, there is a significant correlation between the $Delta m_{15}$ of normal SNe Ia and global ages (morphologies, colours, masses) of their hosts. On average, those normal SNe Ia that are in galaxies from the Red Sequence (early-type, massive, old hosts) have faster declining LCs in comparison with those from the Blue Cloud (late-type, less massive, younger hosts) of the colour-mass diagram. The observed correlations between the $Delta m_{15}$ of normal SNe Ia and hosts parameters appear to be due to the superposition of at least two distinct populations of faster and slower declining normal SNe Ia from older and younger stellar components. We show, for the first time, that the $Delta m_{15}$ of 91bg- and 91T-like SNe is independent of host morphology and colour. The distribution of hosts on the colour-mass diagram confirms the known tendency for 91bg-like SNe to occur in globally red/old galaxies while 91T-like events prefer blue/younger hosts. On average, the youngest global ages of 02cx-like SNe hosts and their positions in the colour-mass diagram hint that these events likely originate from young population, but they differ from 91T-like events in the LC decline rate. Finally, we discuss the possible explosion channels and present our favoured SN Ia models that have the potential to explain the observed SN-host relations.
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The Supernova Cosmology Project has conducted the `See Change programme, aimed at discovering and observing high-redshift (1.13 $leq$ z $leq$ 1.75) Type Ia supernovae (SNe Ia). We used multi-filter Hubble Space Telescope (HST) observations of massive galaxy clusters with sufficient cadence to make the observed SN Ia light curves suitable for a cosmological probe of dark energy at z > 0.5. This See Change sample of SNe Ia with multi-colour light curves will be the largest to date at these redshifts. As part of the See Change programme, we obtained ground-based spectroscopy of each discovered transient and/or its host galaxy. Here we present Very Large Telescope (VLT) spectra of See Change transient host galaxies, deriving their redshifts, and host parameters such as stellar mass and star formation rate. Of the 39 See Change transients/hosts that were observed with the VLT, we successfully determined the redshift for 26, including 15 SNe Ia at z > 0.97. We show that even in passive environments, it is possible to recover secure redshifts for the majority of SN hosts out to z = 1.5. We find that with typical exposure times of 3 - 4 hrs on an 8m-class telescope we can recover ~75% of SN Ia redshifts in the range of 0.97 < z < 1.5. Furthermore, we show that the combination of HST photometry and VLT spectroscopy is able to provide estimates of host galaxy stellar mass that are sufficiently accurate for use in a mass-step correction in the cosmological analysis.
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