Maximally dusty star-forming galaxies: Supernova dust production and recycling in Local Group and high-redshift galaxies

Motivated by recent observations suggesting that core-collapse supernovae may on average produce ~0.3 M_sun of dust, we explore a simple dust production scenario which applies to star-forming galaxies in the local environment (the Magellanic Clouds and possibly the Milky Way) as well as to high redshift (sub- millimeter, QSO, Lyman break) galaxies. We assume that the net dust destruction (due to supernova reverse shock, shocks in the interstellar medium, or astration) is negligible on a timescale of 1 Gyr, in which case the dust mass can be estimated as 0.004 times the star-formation rate (for a Chabrier IMF) multiplied by the duration of the star-formation episode. The model can account for observed dust masses over four orders of magnitude and across the redshift range 0-8.4, with dust production rates spanning five orders of magnitudes. This suggests that star-forming galaxies may be seen as maximally dusty, in the sense that a dominant fraction of the dust-forming elements forged in a supernova eventually will go into the solid phase. In turn, this indicates little destruction of supernova dust or almost complete replenishment, on a short time scale, of any dust that is destroyed.Comment: 14 pages, 3 figures, 1 table, accepted for ApJ

Shaping the dust mass - star-formation rate relation

There is a remarkably tight relation between the observationally inferred dust masses and star-formation rates (SFRs) of SDSS galaxies, Mdust $\propto$ SFR$^{1.11}$ (Da Cunha et al. 2010). Here we extend the Mdust-SFR relation to the high end and show that it bends over at very large SFRs (i.e., dust masses are lower than predicted for a given SFR). We identify several distinct evolutionary processes in the diagram: (1) A star-bursting phase in which dust builds up rapidly at early times. The maximum attainable dust mass in this process is the cause of the bend-over of the relation. A high dust-formation efficiency, a bottom-light initial mass function, and negligible supernova shock dust destruction are required to produce sufficiently high dust masses. (2) A quiescent star-forming phase in which the subsequent parallel decline in dust mass and SFR gives rise to the Mdust-SFR relation, through astration and dust destruction. The dust-to-gas ratio is approximately constant along the relation. We show that the power-law slope of the Mdust-SFR relation is inversely proportional to the global Schmidt-Kennicutt law exponent (i.e., $\sim 0.9$) in simple chemical evolution models. (3) A quenching phase which causes star formation to drop while the dust mass stays roughly constant or drops proportionally. Combined with merging, these processes, as well as the range in total baryonic mass, give rise to a complex population of the diagram which adds significant scatter to the original Mdust-SFR relation. (4) At very high redshifts, a population of galaxies located significantly below the local relation is predicted.Comment: 5 pages, 1 figure, ApJL, in pres

Early gray dust formation in the type IIn SN 2005ip

The physical characteristics of dust formed in supernovae is poorly known. In this paper, we investigate the extinction properties of dust formed in the type IIn SN 2005ip. The observed light curves of SN 2005ip all exhibit a sudden drop around 50 days after discovery. This has been attributed to dust formation in the dense circumstellar medium. We modeled the intrinsic light curves in six optical bands, adopting a theoretical model for the luminosity evolution of supernovae interacting with their circumstellar material. From the difference between the observed and intrinsic light curves, we calculated extinction curves as a function of time. The total-to-selective extinction ratio, $R_V$, was determined from the extinction in the B and V bands. The resulting extinction, $A_V$, increases monotonically up to about 1 mag, 150 days after discovery. The inferred $R_V$ value also increases slightly with time, but appears constant in the range 4.5--8, beyond 100 days after discovery. The analysis confirms that dust is likely formed in SN 2005ip, starting about two months after explosion. The high value of $R_V$, that is, gray dust, suggests dust properties different from of the Milky Way. While this result hinges on the assumed theoretical intrinsic light curve evolution, it is encouraging that the fitted light curves are as expected for standard ejecta and circumstellar medium density structures.Comment: Accepted for publication in A&

On inferring extinction laws in z~6 quasars as signatures of supernova dust

Unusual extinction curves of high-redshift QSOs have been taken as evidence that dust is primarily produced by supernovae at high redshift. In particular, the 3000 A Todini-Ferrara-Maiolino kink in the extinction curve of the z = 6.20 SDSS J1048+4637 has been attributed to supernova dust. Here we discuss the challenges in inferring robust extinction curves of high-redshift QSOs and critically assess previous claims of detection of supernova dust. In particular, we address the sensitivity to the choice of intrinsic QSO spectrum, the need for a long wavelength baseline, and the drawbacks in fitting theoretical extinction curves. In a sample of 21 QSOs at z ~ 6 we detect significant ultraviolet extinction using existing broad-band optical, near-infrared, and Spitzer photometry. The median extinction curve is consistent with a Small Magellanic Cloud curve with A_1450 ~ 0.7 mag and does not exhibit any conspicuous (restframe) 2175 A or 3000 A features. For two QSOs, SDSS J1044-0125 at z = 5.78 and SDSS J1030+0524 at z = 6.31, we further present X-shooter spectra covering the wavelength range 0.9-2.5 um. The resulting non-parametric extinction curves do not exhibit the 3000 A kink. Finally, in a re-analysis of literature spectra of SDSS J1048+4637, we do not find evidence for a conspicuous kink. We conclude that the existing evidence for a 3000 A feature is weak and that the overall dust properties at high and low redshift show no significant differences. This, however, does not preclude supernovae from dominating the dust budget at high redshift.Comment: 13 pages, 13 figures, ApJ, in pres

Magnified or multiply imaged? - Search strategies for gravitationally lensed supernovae in wide-field surveys

Strongly lensed supernovae can be detected as multiply imaged or highly magnified transients. In order to compare the performances of these two observational strategies, we calculate expected discovery rates as a function of survey depth in five grizy filters and for different classes of supernovae (Ia, IIP, IIL, Ibc and IIn). We find that detections via magnification is the only effective strategy for relatively shallow pre-LSST surveys. For survey depths about the LSST capacity, both strategies yield comparable numbers of lensed supernovae. Supernova samples from the two methods are to a large extent independent and combining them increases detection rates by about 50 per cent. While the number of lensed supernovae detectable via magnification saturates at the limiting magnitudes of LSST, detection rates of multiply imaged supernova still go up drastically at increasing survey depth. Comparing potential discovery spaces, we find that lensed supernovae found via image multiplicity exhibit longer time delays and larger image separations making them more suitable for cosmological constraints than their counterparts found via magnification. We find that the ZTF will find about 2 type Ia and 4 core-collapse lensed supernovae per year at a limiting magnitude of 20.6 in the r band. Applying a hybrid method which combines searching for highly magnified or multiply imaged transients, we find that LSST will detect 89 type Ia and 254 core-collapse lensed supernovae per year. In all cases, lensed core-collapsed supernovae will be dominated by type IIn supernovae contributing to 80 per cent of the total counts, although this prediction relies quite strongly on the adopted spectral templates for this class of supernovae. Revisiting the case of the lensed supernova iPTF16geu, we find that it is consistent within the 2\sigma contours of predicted redshifts and magnifications for the iPTF survey.Comment: 16 pages, 11 figures, 2 tables; accepted for publication in MNRA

Dust Destruction Rates and Lifetimes in the Magellanic Clouds

The nature, composition, abundance, and size distribution of dust in galaxies is determined by the rate at which it is created in the different stellar sources and destroyed by interstellar shocks. Because of their extensive wavelength coverage, proximity, and nearly face-on geometry, the Magellanic Clouds (MCs) provide a unique opportunity to study these processes in great detail. In this paper we use the complete sample of supernova remnants (SNRs) in the MCs to calculate the lifetime and destruction efficiencies of silicate and carbon dust in these galaxies. We find dust lifetimes of 22 +- 13 Myr (30 +- 17 Myr) for silicate (carbon) grains in the LMC, and 54 +- 32 Myr (72 +- 43 Myr) for silicate (carbon) grains in the SMC. The significantly shorter lifetimes in the MCs, as compared to the Milky Way, are explained as the combined effect of their lower total dust mass, and the fact that the dust-destroying isolated SNe in the MCs seem to be preferentially occurring in regions with higher than average dust-to-gas (D2G) mass ratios. We also calculate the supernova rate and the current star formation rate in the MCs, and use them to derive maximum dust injection rates by asymptotic giant branch stars and core collapse supernovae. We find that the injection rates are an order of magnitude lower than the dust destruction rates by the SNRs. This supports the conclusion that, unless the dust destruction rates have been considerably overestimated, most of the dust must be reconstituted from surviving grains in dense molecular clouds. More generally, we also discuss the dependence of the dust destruction rate on the local D2G mass ratio, the ambient gas density and metallicity, as well as the application of our results to other galaxies and dust evolution models.Comment: 15 pages, 8 figures, 5 tables, accepted to Ap

A spectroscopic look at the gravitationally lensed type Ia SN 2016geu at z=0.409

The spectacular success of type Ia supernovae (SNe Ia) in SN-cosmology is based on the assumption that their photometric and spectroscopic properties are invariant with redshift. However, this fundamental assumption needs to be tested with observations of high-z SNe Ia. To date, the majority of SNe Ia observed at moderate to large redshifts (0.4 < z < 1.0) are faint, and the resultant analyses are based on observations with modest signal-to-noise ratios that impart a degree of ambiguity in their determined properties. In rare cases however, the Universe offers a helping hand: to date a few SNe Ia have been observed that have had their luminosities magnified by intervening galaxies and galaxy clusters acting as gravitational lenses. In this paper we present long-slit spectroscopy of the lensed SNe Ia 2016geu, which occurred at a redshift of z=0.409, and was magnified by a factor of ~55 by a galaxy located at z=0.216. We compared our spectra, which were obtained a couple weeks to a couple months past peak light, with the spectroscopic properties of well-observed, nearby SNe Ia, finding that SN 2016geu's properties are commensurate with those of SNe Ia in the local universe. Based primarily on the velocity and strength of the Si II 6355 absorption feature, we find that SN 2016geu can be classified as a high-velocity, high-velocity gradient and "core-normal" SN Ia. The strength of various features (measured though their pseudo-equivalent widths) argue against SN 2016geu being a faint, broad-lined, cool or shallow-silicon SN Ia. We conclude that the spectroscopic properties of SN 2016geu imply that it is a normal SN Ia, and when taking previous results by other authors into consideration, there is very little, if any, evolution in the observational properties of SNe Ia up to z~0.4. [Abridged]Comment: 12 pages, 5 figures, 4 tables. Submitted to MNRAS. Comments welcome

On Inferring Extinction Laws in Z -approximately 6 Quasars as Signatures of Supernova Dust

Unusual extinction curves of high-redshift QSOs have been taken as evidence that dust is primarily produced by supernovae at high redshift. In particular, the 3000 A Todini-Ferrara-Maiolino kink in the extinction curve of the z = 6.20 SDSS J1048+4637 has been attributed to supernova dust. Here we discuss the challenges in inferring robust extinction curves of high-redshift QSOs and critically assess previous claims of detection of supernova dust. In particular, we address the sensitivity to the choice of intrinsic QSO spectrum, the need for a long wavelength baseline, and the drawbacks in fitting theoretical extinction curves. In a sample of 21 QSOs at z 6 we detect significant ultraviolet extinction using existing broad-band optical, near-infrared, and Spitzer photometry. The median extinction curve is consistent with a Small Magellanic Cloud curve with A1450 0.7 mag and does not exhibit any conspicuous (restframe) 2175 A or 3000 A features. For two QSOs, SDSS J10440125 at z = 5.78 and SDSS J1030+0524 at z = 6.31, we further present X-shooter spectra covering the wavelength range 0.9-2.5 m. The resulting non-parametric extinction curves do not exhibit the 3000 A kink. Finally, in a re-analysis of literature spectra of SDSS J1048+4637, we do not find evidence for a conspicuous kink. We conclude that the existing evidence for a 3000 A feature is weak and that the overall dust properties at high and low redshift show no significant differences. This, however, does not preclude supernovae from dominating the dust budget at high redshift

Dynamical mass inference of galaxy clusters with neural flows

We present an algorithm for inferring the dynamical mass of galaxy clusters directly from their respective phase-space distributions, i.e. the observed line-of-sight velocities and projected distances of galaxies from the cluster centre. Our method employs normalizing flows, a deep neural network capable of learning arbitrary high-dimensional probability distributions, and inherently accounts, to an adequate extent, for the presence of interloper galaxies which are not bounded to a given cluster, the primary contaminant of dynamical mass measurements. We validate and showcase the performance of our neural flow approach to robustly infer the dynamical mass of clusters from a realistic mock cluster catalogue. A key aspect of our novel algorithm is that it yields the probability density function of the mass of a particular cluster, thereby providing a principled way of quantifying uncertainties, in contrast to conventional machine learning approaches. The neural network mass predictions, when applied to a contaminated catalogue with interlopers, have a mean overall logarithmic residual scatter of 0.028 dex, with a log-normal scatter of 0.126 dex, which goes down to 0.089 dex for clusters in the intermediate to high mass range. This is an improvement by nearly a factor of four relative to the classical cluster mass scaling relation with the velocity dispersion, and outperforms recently proposed machine learning approaches. We also apply our neural flow mass estimator to a compilation of galaxy observations of some well-studied clusters with robust dynamical mass estimates, further substantiating the efficacy of our algorithm.Comment: 14 pages, 9 figures, 1 table. Improved approach, saliency maps adde

Rapid formation of large dust grains in the luminous supernova SN 2010jl

The origin of dust in galaxies is still a mystery. The majority of the refractory elements are produced in supernova explosions but it is unclear how and where dust grains condense and grow, and how they avoid destruction in the harsh environments of star-forming galaxies. The recent detection of 0.1-0.5 solar masses of dust in nearby supernova remnants suggests in situ dust formation, while other observations reveal very little dust in supernovae the first few years after explosion. Observations of the bright SN 2010jl have been interpreted as pre-existing dust, dust formation or no dust at all. Here we report the rapid (40-240 days) formation of dust in its dense circumstellar medium. The wavelength dependent extinction of this dust reveals the presence of very large (> 1 micron) grains, which are resistant to destructive processes. At later times (500-900 days), the near-IR thermal emission shows an accelerated growth in dust mass, marking the transition of the supernova from a circumstellar- to an ejecta-dominated source of dust. This provides the link between the early and late dust mass evolution in supernovae with dense circumstellar media.Comment: 62 pages, 13 figures, 1 table. Author version of the Letter to Nature, published online July 9 2014 (Nature, 511, 7509, pp. 326-329 (2014)), prior to the final editorial changes to conform to Journal style; includes Methods and Extended Data Figures and the Supplementary Information. See published version http://www.nature.com/nature/journal/v511/n7509/full/nature13558.htm