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Any complete standardized SNIa data out there?
An unrefereed paper astro-ph/0406437 appeared yesterday in which Ari
Brynjolfsson interprets SNIa data using a "plasma redshift" approach which rejects time dilation as a redshift interpretation. I am not a plasma man but have myself been considering some of the points raised in that paper. This harkens back to a Bruno Leibundgut paper (ARAA 2001, 39,67) in which he addresses the problems with high-z SN observations: "Another discrepancy emerging is the color of the distant objects. .... the distant SNe Ia appear clearly bluer than the nearby objects. ..... A striking discrepancy is that none of the slowly declining and, hence, very luminous objects observed in the nearby sample have been discovered at large distances. ... This is clearly contrary to what is expected from a Malmquist bias ..." In a nutshell, the problem is that SNIa are modelled to occur at varying absolute brightness, characterized by the brightest having brighter absolute magnitude (obviously), bluer colors and broader light curve, ie, slower increase and decline in brightness. Therefore, at very great distance (high z), one would expect a preponderance of the brightest SN (due to Malmquist), thus the bluest colors and the broadest light curves. As Leibundgut notes, the bluest colors do occur, but the broadest light curves do not. The high-z SN are characterized by blue colors but light curves which are *less than average* compared with the low-z SN. How can this be? The obvious departure point is the currently assumed redshift-dependent light curve broadening. It is assumed, in all today's projects, that the SN light curves are dilated by (1+z) so, as an operational starting point, all the light curves are compressed into the "rest frame" standard and analyzed from that point on. This yields the Liebundgut conundrum. Obviously a line of inquiry would be that the most distant SN are in fact the intrinsically brightest (thus accounting for their blue colors), that a Malmquist effect is allowing us to see only the brightest, and that they thus must be visibly dimmer than currently modelled. Brynjolfsson uses a "plasma red****" interpretation to handle this situation, but my own interpretation is that a Randall-Sundrum 5D geometry is diffusing light more broadly than modelled by 3D-bound systems and that this accounts for both light dimming at high-z and the old "numbers problem" that faint objects seem over-numerous. This would produce the current observed situation, of broad light curves and blue colors, but faint observed brightness maxima, provided time dilation is discarded. However, all our models are unimportant compared with the task of reconciling our models to the available data. To that end what is needed is a uniform table of SNIa data featuring redshift, blueness, apparent magnitude and presumed stretch factor. The recent papers of new SNIa data present their information very differently; it is problematic to align these data into a consistent presentation. Does anyone know of an on-line database which presents all these factors in a consistent format? My own premise is that the high-z SNIa data will be found to support a Randall-Sundrum 5D geometry without any time dilation. I'm happy for my premise to be shredded, er, disproven by the data, but first I need that data. Does anyone have a pointer to uniform complete SNIa data which includes absolute magnitude, blueness, and redshift? thanks, Eric Eric Flesch Wellington, New Zealand |
#2
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Any complete standardized SNIa data out there?
(Eric Flesch) writes:
.... I'm happy for my premise to be shredded, er, disproven by the data, but first I need that data. Does anyone have a pointer to uniform complete SNIa data which includes absolute magnitude, blueness, and redshift? Ultra-short answer: no. Longer answer: I think what you might hope to find is a collection of slightly different information: the observed quantities. It would be nice to have a table of: - apparent magnitude(s) at maximum light, together with passband(s) in which the magnitude(s) was measured - estimate of redshift If the table included at least two magnitudes at maximum light in different passbands, you could calculate a color. The redshifts may present some problems: in some cases, one can measure the redshift of an unambiguous host galaxy and assign it to the supernova. In other cases, however, there may be no visible host galaxy, or several possible hosts, or the host may be too faint for a redshift measurement. In some cases, astronomers estimate the redshift from a spectrum of the supernova; you _might_ want to pick a sample of events for which the redshift was determined in a uniform manner. With this information, you could then compare the measurements to your favorite models of a) supernova properties and b) cosmological parameters. You asked in your message for a table of "absolute magnitudes" of supernovae, but of course, those depend on the cosmology one adopts to convert the apparent to absolute magnitudes. I share your wish for such a compilation of data, but I wouldn't bet on finding one any time soon :-( Michael Richmond |
#3
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Any complete standardized SNIa data out there?
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#4
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Any complete standardized SNIa data out there?
Here are links to various papers, discussions and sites which concern
the interpretation of SN1a light curves. Some are recycled from the thread "Plasma redshift, coronal heating . . ." which groups.google won't let me write to, since the last activity was over a month ago. See also the "Supernova & GRB time dilation" thread which I can't write to either. A paper by Jerry W. Jensen which I think is highly significant: Supernovae Light Curves: An Argument for a New Distance Modulus http://arxiv.org/abs/astro-ph/0404207 2004 April 6 He contends that the conventional interpretation (such as by the researchers at the Supernovae Cosmology Project http://www-supernova.lbl.gov) of supernovae light curves is flawed. His argues that his corrections to the conventional analysis show that there is there is no time dilation - and therefore no reason to believe the Universe is expanding according to the Big Bang Theory. He offers an explanation of the cosmological redshift with a theory known as CREIL - Coherent Raman Effects on Incoherent Light. But maybe a plasma redshift theory could explain it to. This paper refers to "Malmquist Type II Bias" which is explained in a 1997 paper by P. Teerikorpi. (See especially page 109 and the example near the bottom of page 112.) Observation Selection Bias Affecting the Determination of the Extragalactic Distance Scale http://nedwww.ipac.caltech.edu/level...orpi/paper.pdf An earlier paper by Jerry Jensen and Jacques Moret-Baily explains CREIL: Propagation of electromagnetic waves in space plasma http://arxiv.org/abs/astro-ph/0401529 2004 January 25 There have been lively discussions of Jerry Jensen's paper at http://www.badastronomy.com . (Ideally, I think, these would occur on the moderated, public, fully archived and searchable sci.astro.research - but maybe the moderation and propagation delays make the instant response of the Web-based discussion server more attractive.) Against the Mainstream: Cutting the Cord on the Big Bang http://www.badastronomy.com/phpBB/viewtopic.php?t=14433 and an earlier one Bad Supernova Data Reduction http://www.badastronomy.com/phpBB/viewtopic.php?t=14269 These discussions give more insight into the critique Jenson makes of the conventional SN1a approach. In the earlier discussion, on 15 June, he says that he has been writing to the conventional researchers for over a year before April 2004 and "My emails ... are never answered if I ask anything more than the most innocent questions." I think his critique of the conventional SN1a approach is very credible. I won't try to summarise his critique here. Ari Brynjolfsson has published a second paper - with a new analysis of supernovae light curves, according to his plasma redshift theory, again showing no time dilation. Plasma Redshift, Time Dilation, and Supernovas Ia http://arxiv.org/abs/astro-ph/0406437 2004 June 19 According to Eric Flesch (in the "Plasma redshift ..." thread), a paper with unadjusted light curves for 11 SNe at redshifts 0.35 to 0.86: http://arxiv.org/abs/astro-ph/0309368 A page about SN1a light curves and spectra, which Gordon D. Pusch cited when debating Eric Flesch's views about these light curves: http://www.nd.edu/~kkrisciu/supernovae.html The Online Supernova Spectrum Archive: http://bruford.nhn.ou.edu/~suspect/ I believe anyone who is interested in SN1a observations and interpretations will find Jerry Jenson's paper and the ensuing discussion fascinating. I think this critique can be completely decoupled from CREIL or whatever theories may explain the redshift of galaxies and quasars without the Big Bang. - Robin http://astroneu.com |
#6
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Any complete standardized SNIa data out there?
In article ,
you write: Maybe someone on this newsgroup who is more familiar with the terminology would be able to tell me whether the tables of data for the 11 lightcurves starting on page 43 of Knopf et al`s 12 september 2003 paper are k corrected or not. ( http://arxiv.org/abs/astro-ph/0309368 ) Knop, not Knopf. Now published in 2004 ApJ 598, 102. The lightcurves in the tables are k-corrected. I'm not sure why you think that makes any difference, but if you think so, you could probably work out how the k-correction was done and back it out. At the very least, you should be able to estimate how big the correction is and how much it changes during the time a given SN is observed. (I haven't tried this, but I certainly hope and expect the authors have given relevant details, probably via references.) |
#7
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Any complete standardized SNIa data out there?
Trying to understand and critique the way these SN observations have
been processed and interpreted is a big task. I don't have time at present, but I would want to read this paper (astro-ph/0309368) to about page 25 and the relevant parts of every paper the authors cite. Then, I would compare my understanding of this process with the account given by Jerry Jensen. Only then could I evaluate Jerry's critiques. Trying to poke into the beast from the outside with a few quick stabs is unlikely to result in real enlightenment. It needs to be fully disassembled and all its bits laid out in the sunshine. Here is my understanding of these graphs of the lightcurves (Fig 1 and 2). The description on page 10 does not clearly describe the graphs: Appendix A tabulates all of the lightcurve data for the eleven HST supernovae in this paper. The lightcurves for these supernovae (and the F675W WFPC2 image nearest maximum light) are shown in Figures 1 and 2. However the description in Appendix A is more detailed: Tabulated below are lightcurve data for the eleven HST supernovae presented in this paper. For each event, there are two lightcurves, one for R-band and one for I-band. All photometry has been color-corrected to the standard Bessel filters as described in section 3, using color corrections which assume the lightcurve parameters in Table 3. This indicates that the graphs are directly derived from the tabular data in Appendix A. My understanding is that these show the exact observer epochs of each observation, specifying which telescope was used, with a flux for each observation. These fluxes are relative to a zeropoint for each table, which I guess is intended to be something like the flux observed from the area of the supernova before and after its light was detectable. These flux figures are not, however, what was observed - they are "color corrected" versions of the original observations. The observations were made through various colour filters, depending on the telescope. There were various reasonably predictable errors due to absorption in the Earth's atmosphere for the ground-based telescopes. Ideally, the way to observe each SN at a given redshift would be through a filter specifically made for that redshift, so that the telescope's filter response, convolved with its detector response, when receiving the redshifted light, selects the same spectrum of photons as a standard filter and detector would with no redshift. This is impossible for various reasons, and so they use a complex "color-correction" algorithm to convert their observations into what they think would be observed through R and I filters if there had been no redshift. (From what I know, this is before and totally separate from the "K-correction", whatever that is.) There's plenty of scope for problems here. Any such correction must involve assumptions about the spectrum of the SN. In particular, it involves assumptions about how luminosity integrated through a filter response over one range of wavelengths (as observed) correlates with the luminosity over another range of wavelengths (as we would like to observe). This is tricky enough, but as Sean wrote earlier, there is the additional problem of the spectrum changing over time as the SN grows generally brighter and dimmer. It seems likely (I haven't checked) that the light-curve in redder wavelengths would generally be longer in time, especially in the tail, since temperatures would be dropping and the long wavelengths would remain strongly in the resulting Planck curve for a longer period of time than the short wavelengths. To correct for this, it would not be enough to consider an isolated measurement. The researchers would need to know where in the light-curve this measurement was taken, to place it in some model of cooling-induced spectral changes. If (and I am not saying they do) there was some assumption at this point about time dilation of the light received from high redshift objects, then there could be trouble. The whole approach is dodgy anyway, since it involves assumptions about the SN which may not be correct. As Jerry Jensen points out, there are questions about whether we are really always looking at what we understand as SN type 1a. Even if these objects really do fit this formal definition, there are lots of questions about how these things vary from SN to SN, what the statistics of these variations are etc. Extinction in our galaxy, the host galaxy and all places in-between also need to be considered at some point when trying to determine the peak absolute magnitudes of these SNe. I have not chased the references to see exactly how they do this - but it seems that the *input* parameters for this color-correction process are found in Table 3. All photometry has been color-corrected to the standard Bessel filters as described in section 3, using color corrections which assume the lightcurve parameters in Table 3. My initial understanding of Table 3 is that it contains the redshift of each SN and the *outputs* of various stages of their correction process. Unless the sole input to the color-correction process is the redshift, then from my initial reading, "using color corrections which assume the lightcurve parameters in Table 3." doesn't make sense. I would need to read a lot of material to understand exactly how they color-correct the fluxes we see in Appendix A and the graphs of Fig 1 and 2. However, it is my impression that these tables and graphs give the exact epochs of the observations, unaltered in any way. To check this, consider Table 1, the right column, for SN 1997ek. These are HST observations on 7 days, starting with 5 January 1998 and ending with 16 November 1998. These observations span 315 days. Now look on page 43 at Table 11. The earliest HST observation is on Julian day 50818.93 and the last on 51134.26. The difference is 315.33 days. So the table epochs seem to be raw. The epochs in the graph seem to directly reflect the table epochs. I haven't noticed if they specify what epoch on Earth they regard as the peak of the light-curve (which is something which would result from a lot of crunching, but I have looked at the top right graph in Fig 1 - the I-band filter light curve (as calculated via color-correction, I think) - of SN 1997ek at redshift 0.86. There are two black dots (HST observations) near the peak of their artificial light-curve line and three to the right as it gets dimmer. One more is in the non-linear right end of the graph, where the days 150 to 550 after the assumed peak are compressed horizontally. I assume this is really the two HST observations on Julian days 51126.93 and 51134.26. The left-most black dot looks like it is aligned with 0 on the horizontal scale. I will assume this first observation is on day 50818.93. On that basis, the first 5 observations would have these times from 0: Julian day Relative to Flux 50818.93 50818.93 0 3.83 50824.78 5.85 3.89 50846.74 27.81 1.54 50858.84 39.91 0.75 50871.95 53.02 0.46 Within the limits of the clarity of the graph, the black dots are in exactly the right place for these figures. So the $13.7 billion question is whether the light curves for the high redshift SNe have longer times than those with low redshifts! A wag might point out that the 1998be curve (z=0.644) is clearly shorter than that of 1997as (z=0.355) - while if the SNe themselves were identical explosions, and if the redshift is caused by them moving away from us, then the resulting time-dilation would cause our observation of the 1998be curve to be 21.3% longer. But these curves - the lines themselves - are the product of a lot of interpretation, as are the corrected fluxes. All this is based on sparse observations - and we don't know for sure when the lightcurves really started. Maybe the colour-correction process for high-redshift objects does result in raised flux levels at the tail of the presumed curve - that would make sense if Sean's suggestion is a factor. I wouldn't attempt to divine any more insight without looking at in detail at how the observations are "corrected". Ideally, I would want the original fluxes. - Robin http://astroneu.com |
#8
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Any complete standardized SNIa data out there?
In my previous message I gave an inadequate description of how I
thought the supernovae light curve data was processed. The researchers use the term "color-correction" and "K correction" separately. I am not sure what the former is, but it the term "K correction" is a specific transformation, as described in: The K correction David W. Hogg, Ivan K. Baldry, Michael R. Blanton, Daniel J. Eisenstein http://arxiv.org/abs/astro-ph/0210394 - Robin http://astroneu.com |
#9
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Any complete standardized SNIa data out there?
(Steve Willner) wrote in message ...
In article , you write: Maybe someone on this newsgroup who is more familiar with the terminology would be able to tell me whether the tables of data for the 11 lightcurves starting on page 43 of Knopf et al`s 12 september 2003 paper are k corrected or not. ( http://arxiv.org/abs/astro-ph/0309368 ) Knop, not Knopf. Now published in 2004 ApJ 598, 102. The lightcurves in the tables are k-corrected. I'm not sure why you think that makes any difference, In my two previous posts in this thread I explained why it is neccesary to access non k corrected data but Ill try here again as briefly as possible. If one were able to observe a high redshift SN in B and R bands `close up` one would get a two emmision lightcurves ,..one B one R like so... . . . . . . . . . . . . . . . . .. . . . B R (Notice B is steeper decay and R is less so and appears to be time dilated. Reiss` survey shows IRBV has this progression of faster decays for shorter wavelength lightcurves) Here on Earth we see those two emmision bands redshifted to longer wavelengths ,lets say from BR to RI. So the light, we observe in filters R and I was initially emitted in B and R as illustrated above. My point is that IF the redshift is not caused by a BBT expansion there should not be any time dilation of the observed lightcurves of high redshift SN. This can checked and verified or dismissed simply by taking the two observed lightcurves in R and I of a distant SN and calculating back what the emmision wavelength for the observed R and I bands would be . In this case as I have said they would be emmited in B and R bands. SO,... One simply has to take the two Uncorrected R and I band lightcurves (observed from the high redshift SN) and overlay them with the B and R band lightcurves from Reiss` survey (Reiss survey being low redshift gives us a good representation of what emmision lightcurves of SN for IRBV are). *IF* they match then this is conclusive proof there is no time dilation of high redshift SN ligntcurves contrary to accepted wisdom. I have done so with k corrected HST lightcurves and there is no sign of time dilation using this above method. However I realize that to prove my point absolutely I must do the same with *uncorrected* high redshifted lightcurves. Hence my desire to find uncorrected data . probably work out how the k-correction was done and back it out. At the very least, you should be able to estimate how big the correction is and how much it changes during the time a given SN is observed. (I haven't tried this, but I certainly hope and expect the authors have given relevant details, probably via references.) I believe I *may* have found some uncorrected data in the SCP database. In that site there are downloadable GIF lightcurves of high redshifted SN and no mention of any k correction applied. Unfortunately an email to the site requesting confirmation of whether or not the SCP raw lightcurves are k corrected has not been responded to. Can I then assume the online SCP lightcurves NOT k corrected? Sean |
#10
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Any complete standardized SNIa data out there?
Sean wrote:
I believe I *may* have found some uncorrected data in the SCP database. I can't find any such .gifs with Google. Can you give the URL of these files or of wherever you are looking? Can I then assume the online SCP lightcurves NOT k corrected? I don't think anything like this can be assumed. I am struggling to understand how Knop et al. and the other major papers in this field, process their data. Here is my current, partial, probably inadequate and/or faulty understanding: Referring to Knop et al. http://www.arxiv.org/abs/astro-ph/0309368 the flux (linear brightness) values used in Figs 1 and 2, seem to directly correspond to the values in Appendix A, which can also be found at: http://brahms.phy.vanderbilt.edu/deepsearch/hstpaper/ These have times (horizontal) exactly as observed (as I noted in an earlier post). However the values (vertical) are not the raw observed fluxes - they are the product of some corrections. I found it it confusing trying to figure out exactly how they arrived at these "color corrected" flux values: (p8) For both high- and low-redshift supernovae, color corrections and K-corrections are applied . . . Many paragraphs of details follow - how they figured out the best way of deciding on a curve to represent the total light curve, as it would be with a given filter if observed near to the SN, based on their limited number of observations at various redshifts with various telescopes and filters. My understanding of "fitting" means using the MINUIT program: http://wwwasd.web.cern.ch/wwwasd/cernlib/ http://wwwasdoc.web.cern.ch/wwwasdoc...t/minmain.html to find the values of various variables which optimise (typically minimise) the output of some Fortran function. By coding up some stuff, with light-curve tables and corrected observational data, MINUIT will find how best to place a light-curve, with starting time, width, and maximum flux to the observed data points. Its a dodgy business, but they need a light curve to figure out what the maximum flux was, or would have been if they had observed it at maximum. They also need this light-curve to do various corrections which involve assumptions about the spectrum of the light at any particular point in time. On page 10: The final results of the light-curve fits, including the effect of color corrections and K-corrections are listed in Table 3 ... For each SN, Table 3 contains the stretch factors and a calculated maximum observed magnitude - the magnitude that would (they intend) have been observed through a standard filter on Earth when we received the light from when the SN was at its brightest. (BTW, "magnitude" drives me nuts - brighter is a lower value, so "maximum magnitude" applied numerically means dimmer, whilst in a meaningful sense about brightness, means a lower number.) Column d has this brightest magnitude corrected for host-galaxy extinction. This figure, together with the redshift, goes into their cosmological analysis. The SNe were observed with differing redshifts, on various telescopes with differing filters. Ideally, they would have measured the light curve using a single filter from a location close to each SN. Ordinarily, colour correction - which I understand to be converting a flux (number of photons) value measured with one filter to a value which is what we think would have been observed through another filter - involves precise knowledge of the two filter response curves, and an assumption about the spectrum of light being observed. By "ordinarily", I mean that the spectrum is known. However, the SN spectrum changes over time, so in order to perform color or K corrections, from one filter and observed redshift to some other filter and desired redshift, they need to know the spectrum. Since they don't know the spectrum at all at that time of the photometric measurement, they have to try to estimate it from the generalised spectrum of a similar SN at this particular point in its brightening and dimming light curve. I think this means they need to estimate where in the history of the SN light curve this observation is, in order to do their corrections. An illustration of the way the SN spectrum starts off bluer and ends redder is at: http://supernova.lbl.gov/public/figures/saul_sm.mpg So I think that the sum total of their corrections (For Knop et al. in two stages - color and K) to the flux of each observation needs to be done after they have figured out where in the light-curve, in the SN's timeframe, each observation lies. Generally, as I understand it, what I described above as color correction is in fact K-correction: The K correction Hogg et al http://arxiv.org/abs/astro-ph/0210394 but Knop et al. have two stages. If all their observations were with a single telescope and filter, they probably would have done the corrections in one "K-correction" step. However, they are mixing different telescopes, with different filters, and SN of different redshifts. Section 2.3 explains their process. In order to combine data from different telescopes, color corrections were applied to remove the differences in the spectral responses of the filters relative to the Bessell system (1990PASP..102.1181). For the ground-based telescopes, the filters are close enough to the standard Bessell filters that a single linear color term (measured at each observatory with standard stars) suffices to put the data onto the Bessell system, with most corrections being smaller than 0.01 magnitudes. The WFPC2 filters are different enough from the ground-based filters, however, that a linear term is not sufficient. Moreover, the differences between a SN Ia and standard star spectral energy distribution are significant. In this case, color corrections were calculated by integrating template SN Ia spectra (described below) through the system response. So this first stage seems to be a way of coping with the various telescopes and filters - one would think this has nothing to do with the redshift of the observed light. They then use a "single series of K-corrections" - I guess one particular correction for each SN's redshift - applied to each one of that SN's color corrected flux levels. This seems to be for simplicity, to reduce the number of K corrections and the possibility of errors. The color correction to the nearest standard Bessell filter followed by a K-correction to a rest-frame filter is equivalent to a direct K-correction from the observed filter to the standard rest-frame filter. In practice, we perform the two steps separately so that all photometry may be combined to provide a lightcurve effectively observed through a standard (e.g. R-band) filter, which may then be fit with a single series of K-corrections. The data tabulated in Appendix A have all been color-corrected to the standard Bessell filters. So here they say that Appendix A, and as far as I can tell, the flux levels in Figures 1 and 2, have just been subject to this first level of correction - color correction - and by implication not K-correction, which is to cope with the different redshifts of the SNe. (Why do they publish this half-way corrected stuff, and apparently graph it? I would have thought that the most important thing was the result of the K-correction if they are only going to publish one set of figures. Maybe they sometimes use "color correction" to include both the first "color correction" stage and the second "K-correction" stage.) But if "color correction" is just to cope with differences between telescope filters, with nothing to do with redshift etc. why in Appendix A do they write that this requires something to do with fitted light curves: All photometry has been color-corrected to the standard Bessel Filters as described in section 3, using color corrections which assume the lightcurve parameters in Table 3. ?? I can understand them using redshift and assuming time-dilation of high redshift SN in order to do their K-corrections. In order to correct a particular flux level, they need to know the spectrum at that time, which they don't have - so I think they would figure out where in the assumed light-curve the observation is, in the time-frame of the source, and use that as part of their K-correction from one filter function to another. I can't understand, by reading Knop et al. exactly how the data was transformed - and I couldn't clearly see where Jerry Jensen's charge of assuming time-dilation in the high redshift observations was justified in this paper. But Knop et al. cites (page 10) Nugent, Kim & Perlmutter (http://arxiv.org/abs/astro-ph/0205351) for how they did the color and K corrections. I haven't read this yet. However, I have reason to believe Jerry's charge sticks in the general procedures used by these researchers. For instance, on page 3 of: Measurements of Omega and Lambda from 42 High-Redshift Supernovae Perlmutter et al. http://arxiv.org/abs/astro-ph/9812133 they state clearly that they assume time-dilation in the observations of high redshift SNe: For the supernovae discussed in this paper, the template must be time-dilated by a factor 1 + z before fitting to the observed lightcurves to account for the cosmological lengthening of the supernova timescale Also, in page 16 of the frequently cited: Measurements of the Cosmological Parameters Omega and Lambda from the First 7 Supernovae at z = 0.35 S. Perlmutter et al. http://arxiv.org/abs/astro-ph/9608192 there is another telling sentence: The rising slope of the template light curve before rest-frame day -10 ... This convinces me that they are assuming time-dilation in how the light from high-redshift SN arrives on Earth. I have a long way to go before I am confident of understanding how the observations are transformed into the data which are published. But it seems that Jerry's first charge of assuming time-dilation is correct. This is bad science if the purpose is to test whether or not there is in fact time-dilation in high redshift objects. Maybe they think they settled the matter once and for all in 1996: Observation of Cosmological Time Dilation using Type Ia Supernovae as Clocks G. Goldhaber et al. http://arxiv.org/abs/astro-ph/9602124 - Robin http://astroneu.com |
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