J/A+A/526/A28 SDSS-II supernovae NTT and NOT spectroscopy (Oestman+, 2011)
NTT and NOT spectroscopy of SDSS-II supernovae.
Oestman L., Nordin J., Goobar A., Amanullah R., Smith M., Sollerman J.,
Stanishev V., Stritzinger M.D., Bassett B.A., Davis T.M., Edmondson E.,
Frieman J.A., Garnavich P.M., Lampeitl H., Leloudas G., Marriner J.,
Nichol R.C., Romer K., Sako M., Schneider D.P., Zheng C.
<Astron. Astrophys., 526, A28 (2011)>
=2011A&A...526A..28O 2011A&A...526A..28O
ADC_Keywords: Supernovae ; Surveys ; Spectroscopy
Keywords: methods: observational - techniques: spectroscopic -
supernovae: general - surveys - cosmology: observations
Abstract:
The Sloan Digital Sky Survey II (SDSS-II) Supernova Survey, conducted
between 2005 and 2007, was designed to detect a large number of type
Ia supernovae around z∼0.2, the redshift "gap" between low-z and
high-z supernova searches. The survey has provided multi-band (ugriz)
photometric lightcurves for variable targets, and supernova candidates
were scheduled for spectroscopic observations, primarily to provide
supernova classification and accurate redshifts. We present supernova
spectra obtained in 2006 and 2007 using the New Technology Telescope
(NTT) and the Nordic Optical Telescope (NOT).
We provide an atlas of supernova spectra in the range z=0.03-0.32
that complements the well-sampled lightcurves from SDSS-II in the
forthcoming three-year SDSS supernova cosmology analysis. The sample
can, for example, be used for spectral studies of type Ia supernovae,
which are critical for understanding potential systematic effects when
supernovae are used to determine cosmological distances.
The spectra were reduced in a uniform manner, and special care was
taken in estimating the uncertainties for the different processing
steps. Host-galaxy light was subtracted when possible and the
supernova type fitted using the SuperNova IDentification code (SNID).
We also present comparisons between spectral and photometric dating
using SALT lightcurve fits to the photometry from SDSS-II, as well as
the global distribution of our sample in terms of the lightcurve
parameters: stretch and colour.
Description:
The NTT, located at the La Silla Observatory in Chile, was used for
spectroscopic observations of SDSS-II SN candidates from September to
December in 2006 and 2007. Thirty-four nights were awarded for the
project, out of which 32 had sufficiently good conditions to obtain SN
spectra. Through the course of these nights, 244 spectra of SN
candidates were obtained.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 39 290 Information about the observations
tablea2.dat 107 290 Spectroscopic typing and redshift determination
tablea3.dat 19 290 *Spectral quality
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Note on tablea3.dat: Both these quantities are very rough estimates and are
in most cases likely overestimated.
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See also:
Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 5 I5 --- ID [12778/22284] Source ID number,
<SDSS-II SNNNNNN> in Simbad
7- 10 I4 --- SPID Spectrum SPID (1)
12- 17 A6 --- SN IAU name (YYYYaa)
19- 21 A3 --- Tel [NOT NTT] Telescope used
23- 25 F3.1 arcsec Slit Slit width
27- 30 I4 s Texp Exposure time
32- 35 F4.2 --- Air Airmass
37- 39 F3.1 arcsec See Seeing (2)
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Note (1): Most of the spectra in the table that lack IAU names are
photometric SNe without reliable spectroscopic confirmation and
unclassified objects.
Note (2): The FWHM seeing at 5000Å for the airmass at which the
observations were conducted.
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Byte-by-byte Description of file: tablea2.dat
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Bytes Format Units Label Explanations
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1- 5 I5 --- ID [12778/22284] Source ID number
7- 10 I4 --- SPID Spectrum SPID number
12- 24 A13 --- Type1 SDSS SN type (3)
26- 39 A14 --- Type2 NTT/NOT SN type (4)
41- 46 F6.2 d LC ? Number of days in rest frame from B-band
maximum obtained from the lightcurve (5)
48- 51 F4.2 d e_LC ? Error on LC
52 A1 --- n_LC [p] Note on LC (6)
54- 58 F5.1 d SNID ? Number of days in rest frame from B-band
maximum obtained from SNID (7)
60- 64 F5.1 d e_SNID ? Error on SNID
67- 73 F7.5 --- ze ? SDSS redshift (8)
75- 81 F7.5 --- e_ze ? Error on ze
84- 90 F7.5 --- z ? SNID redshift
92- 98 F7.5 --- e_z ? Error on z
100-107 A8 --- Notes Notes (9)
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Note (3): The overall SDSS type which is based on the results from the NTT/NOT
analysis in combination with spectra from other telescopes.
Note (4): The typing of the individual spectra in this analysis is based on the
result from SNID in combination with a visual inspection. If a subtype could
be determined, this is given in the table, otherwise only the type. Thus, when
the type is given as solely Ia, this means that SNID could not determine if it
is a normal SN Ia or a non-normal (peculiar, SN 1991T or SN 1991bg). In the
cases where all template spectra which could be matched with the input
spectrum with SNID belong to the same SN, the name of the SN is written within
parenthesis. When the type is NotSN or Gal, this usually means that the
transient was too faint, or the observing conditions were not good enough, so
that the contribution from the host galaxy dominates the spectrum.
Note (5): An age is given when the object has been classified as a SN Ia, as
well as there were enough photometry to build a lightcurve.
Note (6): The sign "p" is added after the lightcurve age when the lightcurve
lacked photometry either before or after maximum brightness.
Note (7): If no error is given, there was only one template fitting the
requirements in SNID.
Note (8): The object redshifts from Zheng et al. (in preparation), which have
their origin in SDSS DR7 redshifts in combination with measurements of
both NTT/NOT spectra and other spectra.
Note (9): Additional information as follows:
s = when the SNID type was determined from the host-galaxy subtracted spectrum
f = if there were few template spectra matching the input spectrum, at which
fewer than 5 spectra were used to determine the type, the redshift
and/or the age
v = when the type obtained from SNID was changed after the visual inspection
zg = when the redshift is not obtained from SDSS DR7, and determined from
galaxy lines
zs = when the redshift is not obtained from SDSS DR7, and determined from
SN features
zt = if the redshift was determined through template fitting
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Byte-by-byte Description of file: tablea3.dat
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Bytes Format Units Label Explanations
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1- 5 I5 --- ID [12778/22284] Source ID number
7- 10 I4 --- SPID Spectrum ID number
12- 14 F3.1 --- Host [0/1]?=- Host contamination (10)
15 A1 --- n_Host [e] e when estimation based on an
extrapolation of the photometry
17- 19 F3.1 --- Sloss [0/1] Estimated maximum differential slit loss
due to atmospheric refraction affecting the SN
light in the wavelength region 4000-8000Å
(observed frame)
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Note (10): The estimated host-galaxy contamination in the observed spectra,
i.e. before host-galaxy subtraction has been attempted, for
wavelengths corresponding to the g filter in observed frame.
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 16-May-2011