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The H alpha Galaxy Survey. III. Constraints on supernova progenitors from spatial correlations with H alpha emission

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P. A. James, J. P. Anderson

Astrophysics · Submitted 21 Feb 2006 · 37 references

Pith's verdict: The 40% runaway fraction is built on a null hypothesis that is not actually uniform—the zeroing step in the pixel-ranking statistic inflates the apparent excess—but the qualitative result and the method are worth engaging with.

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CitationJ. P. Anderson, P. A. James. "The H alpha Galaxy Survey. III. Constraints on supernova progenitors from spatial correlations with H alpha emission." arXiv:astro-ph/0602471 (2006). https://pith.science/paper/XCYFP4M5
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The paper

The paper claims

This paper finds that type II supernovae explode in regions of little or no H-alpha emission far more often than expected if they traced star formation, and it interprets the 40% excess as runaway progenitors ejected from their birth sites.

The reading

This paper asks whether supernovae of different types explode where their progenitor stars were born, using H-alpha emission as a map of ongoing high-mass star formation in the host galaxies. It introduces a pixel-statistics test in which each pixel of a continuum-subtracted H-alpha image is ranked by its contribution to the total line flux, so a supernova that perfectly traces star formation would occupy a uniformly random position in the ranked distribution. The result is that type II supernovae do not: 18 of 30 land in the bottom fifth of the ranked flux, against an expectation of 6, an excess of 12 events (40%) in regions with little or no line emission. The authors interpret this excess as a large runaway fraction in type II progenitors, stars that were ejected from their birth sites and exploded later, and the result matters because it changes how supernova counts are converted into star formation rates and how stellar feedback is understood.

What carries the argument

The central object is the normalized cumulative ranked pixel value function (NCRPVF), built from each galaxy's continuum-subtracted H-alpha + [N II] image. Pixels are sorted by increasing count and summed in that order, then the running sum is divided by the total line flux, giving each pixel a value between 0 and 1 that records what fraction of the galaxy's star-formation light is contained in pixels at or below its brightness. The function does the argument's work by converting a supernova position into a number that can be compared with a uniform distribution: a population that perfectly traces star formation should be spread evenly across the NCRPVF, whereas a population scattered randomly through the galaxy accumulates near zero. Two supporting tests, radial growth curves in H-alpha and R-band light and ranked total galaxy fluxes, check the same question at larger spatial scales.

Extended reading notes

Core claim

The central discovery is that core-collapse supernovae do not all trace the H-alpha emission that is supposed to mark their birth population. In the pixel-statistics test, the normalized cumulative ranked pixel value function (NCRPVF) assigns each supernova a number from 0 to 1: 0 means the explosion site lies in a pixel contributing no line flux, and 1 means it lies in the pixel carrying the galaxy's final increment of H-alpha flux. If type II supernovae were drawn from the same population as the line emission, their NCRPVF values should be uniform; instead 18 of 30 have values below 0.2 when 6 are expected, a 40% excess. The paper reads this as evidence that a large fraction of type II progenitors are runaway stars, and it shows that the projected velocities needed to reach the observed sites from the nearest bright H II region, 28 to 155 km/s, match the velocities of known OB runaways. In the same analysis type Ib and Ic supernovae are formally consistent with tracing the emission, and type Ia supernovae mostly avoid star-forming regions, though up to about 42% may be associated with ongoing star formation.

Load-bearing premise

The load-bearing assumption is that H-alpha emission traces every site of high-mass star formation and that surveys find supernovae as easily in faint regions as in bright ones; if either fails, a star-formation-tracing population would not necessarily produce flat ranked-flux values, and the 40% excess could be an artifact of the tracer or the sample.

Editorial extensions

If this is right

  • Type II supernova counts cannot be treated as a simple one-to-one spatial tracer of current star formation, because a substantial fraction of explosions occur away from regions of brightest H-alpha emission.
  • The 40% excess at low NCRPVF implies that either a large fraction of massive stars are runaways or that H-alpha misses a comparable fraction of star formation, and both alternatives alter how supernova rates are used to measure star formation histories.
  • Type Ib and Ic supernovae are more faithful tracers of active star formation than type II, and their central concentration supports a link between stripped-envelope supernovae and high-metallicity or high-mass environments.
  • The type Ia distribution, mostly tracing old stellar light but with up to 42% correlated with H-alpha, is consistent with a prompt/tardy two-population model in which some type Ia rates should track recent star formation.
  • Galaxy-integrated core-collapse rates scale roughly linearly with host luminosity and star formation rate, so global supernova-rate measurements remain usable even though the spatial correspondence with H-alpha is imperfect.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

  • Inference: if the runaway interpretation is correct, the same NCRPVF excess should be stronger for higher-mass progenitors and should correlate with a high binary fraction among type II progenitors, because the binary-supernova channel can eject up to roughly half of massive stars.
  • Inference: the NCRPVF test could be applied to other transients such as long gamma-ray bursts or superluminous supernovae; if those behave like type Ib/Ic instead of type II, it would sharpen the connection between explosion type, progenitor mass, and ejection history.
  • Inference: the alternative explanation, that H-alpha misses 40% of star formation, predicts that low-NCRPVF supernova sites should appear in dust-penetrating tracers such as mid-infrared or radio continuum; that is a testable prediction the paper leaves implicit.
Original abstract

Aims: We attempt to constrain progenitors of the different types of supernovae from their spatial distributions relative to star formation regions in their host galaxies, as traced by H alpha + NII line emission. Methods: We analyse 63 supernovae which have occurred within galaxies from our H alpha survey of the local Universe. Three statistical tests are used, based on pixel statistics, H alpha radial growth curves, and total galaxy emission-line fluxes. Results: Many more type II supernovae come from regions of low or zero emission line flux than would be expected if the latter accurately traces high-mass star formation. We interpret this excess as a 40% `Runaway' fraction in the progenitor stars. Supernovae of types Ib and Ic do appear to trace star formation activity, with a much higher fraction coming from the centres of bright star formation regions than is the case for the type II supernovae. Type Ia supernovae overall show a weak correlation with locations of current star formation, but there is evidence that a significant minority, up to about 40%, may be linked to the young stellar population. The radial distribution of all core-collapse supernovae (types Ib, Ic and II) closely follows that of the line emission and hence star formation in the their host galaxies, apart from a central deficiency which is less marked for supernovae of types Ib and Ic than for those of type II. Core-collapse supernova rates overall are consistent with being proportional to galaxy total luminosities and star formation rates; however, within this total the type Ib and Ic supernovae show a moderate bias towards more luminous host galaxies, and type II supernovae a slight bias towards lower-luminosity hosts.

The compiled record

The paper's own sentences, arranged, kept beside the review and separate from it. Each label is drawn from a closed vocabulary; the number beside it is the probability the classifier gave that label. Numbers in the tables are the authors', checked by code. No sentence in this record was written by a model.

Compiled by classifier-1.13.0 via TypeSafe API, question bank abstract-p1-20260923, 2026-09-23: 1 request, 7,200 input tokens.

What the abstract itself states, as probabilities: claims first 0.03 · states limitation 0.42 · human participants 0.02 · controlled comparison 0.31 · randomized assignment 0.01 · states quantitative result 0.98 · compares with prior results 0.41 · mentions code or data availability 0.02.

The abstract, sentence by sentence

arXiv listing abstract v1. Results and the main claim are underlined; .

Aims: We attempt to constrain progenitors of the different types of supernovae from their spatial distributions relative to star formation regions in their host galaxies, as traced by H alpha + NII line emission. Methods: We analyse 63 supernovae which have occurred within galaxies from our H alpha survey of the local Universe. Three statistical tests are used, based on pixel statistics, H alpha radial growth curves, and total galaxy emission-line fluxes. Results: Many more type II supernovae come from regions of low or zero emission line flux than would be expected if the latter accurately traces high-mass star formation. We interpret this excess as a 40% `Runaway' fraction in the progenitor stars. Supernovae of types Ib and Ic do appear to trace star formation activity, with a much higher fraction coming from the centres of bright star formation regions than is the case for the type II supernovae. Type Ia supernovae overall show a weak correlation with locations of current star formation, but there is evidence that a significant minority, up to about 40%, may be linked to the young stellar population. The radial distribution of all core-collapse supernovae (types Ib, Ic and II) closely follows that of the line emission and hence star formation in the their host galaxies, apart from a central deficiency which is less marked for supernovae of types Ib and Ic than for those of type II. Core-collapse supernova rates overall are consistent with being proportional to galaxy total luminosities and star formation rates; however, within this total the type Ib and Ic supernovae show a moderate bias towards more luminous host galaxies, and type II supernovae a slight bias towards lower-luminosity hosts.

background contribution method result interpretation main claim

What the classifier reports for each sentence. The number is the probability it gave the label.
#sentencerolethe authors' own workstates the main conclusionstrength
s0 Aims: We attempt to constrain progenitors of the different types of supernovae from their spatial distributions relative to star formation regions in their host galaxies, as traced by H alpha + NII line emission. contribution 0.82 0.51 0.05 hedged possibility 0.42
s1 Methods: We analyse 63 supernovae which have occurred within galaxies from our H alpha survey of the local Universe. method 0.95 0.93 0.02 asserted 0.91
s2 Three statistical tests are used, based on pixel statistics, H alpha radial growth curves, and total galaxy emission-line fluxes. method 1.00 0.90 0.02 asserted 0.96
s3 Results: Many more type II supernovae come from regions of low or zero emission line flux than would be expected if the latter accurately traces high-mass star formation. result 1.00 0.95 0.46 asserted 1.00
s4 We interpret this excess as a 40% `Runaway' fraction in the progenitor stars. interpretation 1.00 0.86 0.22 asserted 0.85
s5 Supernovae of types Ib and Ic do appear to trace star formation activity, with a much higher fraction coming from the centres of bright star formation regions than is the case for the type II supernovae. result 1.00 0.94 0.13 asserted 0.97
s6 Type Ia supernovae overall show a weak correlation with locations of current star formation, but there is evidence that a significant minority, up to about 40%, may be linked to the young stellar population. result 1.00 0.93 0.09 hedged possibility 0.85
s7 The radial distribution of all core-collapse supernovae (types Ib, Ic and II) closely follows that of the line emission and hence star formation in the their host galaxies, apart from a central deficiency which is less marked for supernovae of types Ib and Ic than for those of type II. result 1.00 0.94 0.16 asserted 1.00
s8 Core-collapse supernova rates overall are consistent with being proportional to galaxy total luminosities and star formation rates; however, within this total the type Ib and Ic supernovae show a moderate bias towards more luminous host galaxies, and type II supernovae a slight bias towards lower-luminosity hosts. result 1.00 0.93 0.11 hedged possibility 0.85

What kind of paper the classifier reports this is: empirical study 1.00 · evidence from analysis of existing data 0.90.

What was examined, and what was not

sources read
  • arXiv listing abstract v1
not examined
  • full text
  • figures and tables
  • references and citing sentences
  • relations to other papers
levels run
  • P abstract
not run
  • S sections
  • T body sentences
  • C citations
  • R cross-paper relations

Every quoted sentence on this record is the authors'. Every label is from Pith's closed vocabulary, with the probability shown beside it. Every number in the measurements table is the authors', checked by code. Record as JSON

Figures
Figure 1. Positions of Type II supernovae (circles) overlaid on negative images showing the distribution of Hα+[Nii] emission. The scale bars are 20′′ in length. (Continued over.)
Figure 2. Positions of Type II supernovae (circles) overlaid on negative images showing the distribution of Hα+[Nii] emission. The scale bars are 20′′ in length
Figure 3. Positions of Type Ib and Ic supernovae (circles) overlaid on negative images showing the distribution of Hα+[Nii] emission. The scale bars are 20′′ in length. pixels from the centres of the highest surface brightness star formation regions. Alongside this ranked distribution of individual pixel values we also form the corresponding cumulative distribution, by summing the pixel counts in the ranked sequence, giving a sequence which counts up to the total emission line flux from the galaxy. We finally divide this cumulative rank sequence by the total emission line flux, and set the…
Figure 4. Positions of Type Ia supernovae (circles) overlaid on negative images showing the distribution of Hα+[Nii] emission. The scale bars are 20′′ in length. this same star forming population, then SNe should be equally likely to come from any part of the NCRPVF. Thus, over a long period of time, the many pixels contributing to the 0-0.1 section of the NCRPVF contribute as much to the total star formation rate of the galaxy, and hence should host as many SNe, as the few bright pixels comprising the 0.9-1.0 section. Thus, the test we perform is to see whether the positions of the…
Figure 5. Positions of unclassified supernovae (circles) overlaid on negative images showing the distribution of Hα+[Nii] emission. The scale bars are 20′′ in length
Figure 6. Illustrative example showing the calculation of the NCRPVF index for SN2002A in UGC 3804. The larger points/thicker curved line shows the ranked pixel values plotted against number in the ranked pixel sequence; the smaller points/thinner line shows the cumulative counts for each pixel, vertically scaled to fit. The pixel containing the location of SN2002A has a value of 4.5 counts, corresponding to an NCRPVF index of 0.401 as shown. exact pixel value at the SN location by the median pixel value in the 3×3 pixel box centred on that location. In almost all cases this made no…
Figure 7. Histograms of the positions of the SN-containing pixels within the cumulative Hα+[Nii] flux distributions for the 30 Type II supernovae (solid line); and for all 38 core-collapse supernovae (dashed line). 4.2. Core-collapse supernovae
Figure 8. Histogram of the positions of the SN-containing pixels within the cumulative Hα+[Nii] flux distributions for the 12 Type Ia supernovae (solid line). no strong biases should be caused by the incompleteness of type information; whatever the types of the unclassified SNe, their inclusion in Figs. 7 and 8 would have little or no effect on our conclusions. 5. Study of the radial distribution of SNe locations, relative to SF and R-band light in host galaxies 5.1. Methods In this section we perform a statistical test related to that in the previous section, but in this case specifically to…
Figure 9. (a) Histograms of fractional Hα+[Nii] fluxes within the locations of 30 Type II supernovae (solid line); and all 38 core-collapse supernovae (dashed line). (b) Histograms of fractional R-band fluxes within the locations of 30 Type II supernovae (solid line); and all 38 core-collapse supernovae (dashed line)
Figure 10. Histogram of (a) fractional Hα+[Nii] fluxes, and (b) fractional R-band fluxes, within the locations of the 12 Type Ia supernovae SN detection rates, even in near-IR searches (Mannucci et al., 2003). The second possible explanation is that there is an additional emission-line component at the centres of these galaxies which is not related to star formation, and hence not linked to CC SNe. Such a component could be related to AGN (although most of these galaxies do not show strong unresolved central emission-line sources) or to the extended nuclear emission-line sources noted by…
Figure 11. (a) Histograms of the locations of galaxies in the ranked cumulative Hα+[Nii] distributions for 30 type II supernovae (solid line) ; and all 38 core-collapse supernovae (dashed line). (b) Histograms of the locations of galaxies in the ranked cumulative R-band luminosity distributions for 30 type II supernovae (solid line); and all 38 core-collapse supernovae (dashed line)
Figure 12. Histogram of the locations of the galaxies hosting the 12 Type Ia supernovae in (a) the ranked cumulative Hα+[Nii] distribution and (b) the ranked cumulative R-band light distribution. numbers from low-luminosity galaxies. R-band luminosity appears a better predictor of SNIa rates in these galaxies than star formation rate. 6.4. All and unclassified SNe We repeated this analysis for the positions of all 63 SN-hosting galaxies within the total star formation distribution and within the total R-band light distribution. Both tests show a small bias towards low values (means…
Figure 13. (a) Histograms of the locations of galaxies in the ranked cumulative Hα+[Nii] distributions for all 63 super￾novae in the present study (solid line); and for the 13 unclassified supernovae (dashed line). (b) Histograms of the locations of galaxies in the ranked cumulative R-band luminosity distributions for all 63 supernovae in the present study (solid line); and for the 13 unclassified supernovae (dashed line). SN UGC D(Mpc) Rp( ′′) Rp(kpc) V⋆(km s−1 ) 2005ad 1954 18.1 10.2 0.90 41 2004A 10521 15.0 10.9 0.79 36 2003hr 4362 33.1 20.2 3.24 147 2003Z 4779 21.3 9.5 0.98 45 1969L 2193…

Figures reproduced from arXiv:astro-ph/0602471 by the authors.

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