Edward Leocadio Gomez

A cool dust factory in the crab nebula: A Herschel study of the filaments

Whether supernovae are major sources of dust in galaxies is a long-standing debate. We present infrared and submillimeter photometry and spectroscopy from the Herschel Space Observatory of the Crab Nebula between 51 and 670 μm as part of the Mass Loss from Evolved StarS program. We compare the emission detected with Herschel with multiwavelength data including millimeter, radio, mid-infrared, and archive optical images. We carefully remove the synchrotron component using the Herschel and Planck fluxes measured in the same epoch. The contribution from line emission is removed using Herschel spectroscopy combined with Infrared Space Observatory archive data. Several forbidden lines of carbon, oxygen, and nitrogen are detected where multiple velocity components are resolved, deduced to be from the nitrogen-depleted, carbon-rich ejecta. No spectral lines are detected in the SPIRE wavebands; in the PACS bands, the line contribution is 5% and 10% at 70 and 100 μm and negligible at 160 μm. After subtracting the synchrotron and line emission, the remaining far-infrared continuum can be fit with two dust components. Assuming standard interstellar silicates, the mass of the cooler component is 0.24+0.32 – 0.08 M ☉ for T = 28.1+5.5 – 3.2 K. Amorphous carbon grains require 0.11 ± 0.01 M ☉ of dust with T = 33.8+2.3 – 1.8 K. A single temperature modified blackbody with 0.14 M ☉ and 0.08 M ☉ for silicate and carbon dust, respectively, provides an adequate fit to the far-infrared region of the spectral energy distribution but is a poor fit at 24-500 μm. The Crab Nebula has condensed most of the relevant refractory elements into dust, suggesting the formation of dust in core-collapse supernova ejecta is efficient.

Dust in historical Galactic Type Ia supernova remnants with Herschel

The origin of interstellar dust in galaxies is poorly understood, particularly the relative contributions from supernovae and the cool stellar winds of low-intermediate-mass stars. Recently, large masses of newly formed dust have been discovered in the ejecta of core-collapse supernovae. Here, we present Herschel Photodetector Array Camera and Spectrometer (PACS) and Spectral and Photometric Imaging Receiver (SPIRE) photometry at 70–500 m of the historical, young supernova remnants: Kepler and Tycho, both thought to be the remnants of Type Ia explosion events. We detect a warm dust component in Kepler’s remnant with and mass ; this is spatially coincident with thermal X-ray emission and optical knots and filaments, consistent with the warm dust originating in the circumstellar material swept up by the primary blast wave of the remnant. Similarly for Tycho’s remnant, we detect warm dust at with mass . Comparing the spatial distribution of the warm dust with X-rays from the ejecta and swept-up medium, and H emission arising from the post-shock edge, we show that the warm dust is swept up interstellar material. We find no evidence of a cool (25–50 K) component of dust with mass ≥0.07 M⊙ as observed in core-collapse remnants of massive stars. Neither the warm or cold dust components detected here are spatially coincident with supernova ejecta material. We compare the lack of observed supernova dust with a theoretical model of dust formation in Type Ia remnants which predicts dust masses of 88(17) × 10−3 M⊙ for ejecta expanding into ambient surrounding densities of 1(5) cm−3. The model predicts that silicon- and carbon-rich dust grains will encounter, at most, the interior edge of the observed dust emission at ∼400 years, confirming that the majority of the warm dust originates from swept-up circumstellar or interstellar grains (for Kepler and Tycho, respectively). The lack of cold dust grains in the ejecta suggests that Type Ia remnants do not produce substantial quantities of iron-rich dust grains and has important consequences for the ‘missing’ iron mass observed in ejecta. Finally, although, we cannot completely rule out a small mass of freshly formed supernova dust, the Herschel observations confirm that significantly less dust forms in the ejecta of Type Ia supernovae than in the remnants of core-collapse explosions.

Submillimetre Variability of Eta Carinae: cool dust within the outer ejecta

Previous submillimetre (submm) observations detected 0.7 M⊙ of cool dust emission around the luminous blue variable (LBV) star η Carinae. These observations were hindered by the low declination of η Carinae and contamination from free–free emission originating from the stellar wind. Here, we present deep submm observations with LABOCA at 870 μm, taken shortly after a maximum in the 5.5-year radio cycle. We find a significant difference in the submm flux measured here compared with the previous measurement: the first indication of variability at submm wavelengths. A comparison of the submm structures with ionized emission features suggests the 870 μm is dominated by emission from the ionized wind and not thermal emission from dust. We estimate of dust surrounding η Carinae. The spatial distribution of the submm emission limits the mass loss to within the last thousand years, and is associated with mass ejected during the great eruptions and the pre-outburst LBV wind phase; we estimate that η Carinae has ejected >40 M⊙ of gas within this time-scale.

Robotic telescopes in education

The power of robotic telescopes to transform science education has been voiced by multiple sources, since the 1980s. Since then, much technical progress has been made in robotic telescope provision to end users via a variety of different approaches. The educational transformation hoped for by the provision of this technology has, so far, yet to be achieved on a scale matching the technical advancements. In this paper, the history, definition, role and rationale of optical robotic telescopes with a focus on their use in education is provided. The current telescope access providers and educational projects and their broad uses in traditional schooling, undergraduate and outreach are then outlined. From this background, the current challenges to the field, which are numerous, are then presented. This review is concluded with a series of recommendations for current and future projects that are apparent and have emerged from the literature.

Using dust, gas and stellar mass selected samples to probe dust sources and sinks in low metallicity galaxies

We combine samples of nearby galaxies with Herschel photometry selected on their dust, metal, Hi, and stellar mass content, and compare these to chemical evolution models in order to discriminate between different dust sources. In a companion paper, we used a Hi-selected sample of nearby galaxies to reveal a sub-sample of very gas rich (gas fraction > 80 per cent) sources with dust masses significantly below predictions from simple chemical evolution models, and well below Md/M∗ and Md/Mgas scaling relations seen in dust and stellar-selected samples of local galaxies. We use a chemical evolution model to explain these dust-poor, but gas-rich, sources as well as the observed star formation rates (SFRs) and dust-to-gas ratios. We find that (i) a delayed star formation history is required to model the observed SFRs; (ii) inflows and outflows are required to model the observed metallicities at low gas fractions; (iii) a reduced contribution of dust from supernovae (SNe) is needed to explain the dust-poor sources with high gas fractions. These dust-poor, low stellar mass galaxies require a typical core-collapse SN to produce 0.01−0.16 M� of dust. To match the observed dust masses at lower gas fractions, significant grain growth is required to counteract the reduced contribution from dust in SNe and dust destruction from SN shocks. These findings are statistically robust, though due to intrinsic scatter it is not always possible to find one single model that successfully describes all the data. We also show that the dust-to-metals ratio decreases towards lower metallicity.

Iron needles in supernova remnants

It has been suggested by Dwek that iron needles could explain the submillimetre emission from the Cas A supernova remnant (SNR) with only a very small total mass. We investigate whether a similar model holds for the Kepler SNR, and find that its emission could indeed be explained by a dust mass of less than 10?2 M?, dependent on the axial ratio l/a of the needles – which we constrain to be less than 700. But the implied needle model for Kepler is inconsistent with that suggested for Cas A since either the needles would have to have a resistivity one or two orders of magnitude greater than those in Cas A or the electron density in Keplers shocked plasma must be 40 times greater than suggested by X-ray observations. An additional problem with the needle model is that the implied thickness of the needles seems to be implausibly small, if the emission properties are calculated under the usual approximations.

Results from the worldwide coma morphology campaign for comet ISON (C/2012 S1)☆

We present the results of a global coma morphology campaign for comet C/2012 S1 (ISON), which was organized to involve both professional and amateur observers. In response to the campaign, many hundreds of images, from nearly two dozen groups were collected. Images were taken primarily in the continuum, which help to characterize the behavior of dust in the coma of comet ISON. The campaign received images from January 12 through November 22, 2013 (an interval over which the heliocentric distance decreased from 5.1 AU to 0.35 AU), allowing monitoring of the long-term evolution of coma morphology during comet ISON׳s pre-perihelion leg. Data were contributed by observers spread around the world, resulting in particularly good temporal coverage during November when comet ISON was brightest but its visibility was limited from any one location due to the small solar elongation. We analyze the northwestern sunward continuum coma feature observed in comet ISON during the first half of 2013, finding that it was likely present from at least February through May and did not show variations on diurnal time scales. From these images we constrain the grain velocities to ~10 m s−1, and we find that the grains spent 2–4 weeks in the sunward side prior to merging with the dust tail. We present a rationale for the lack of continuum coma features from September until mid-November 2013, determining that if the feature from the first half of 2013 was present, it was likely too small to be clearly detected. We also analyze the continuum coma morphology observed subsequent to the November 12 outburst, and constrain the first appearance of new features in the continuum to later than November 13.99 UT.

Non‐spherical evolution of the line‐driven wind instability

In this paper, we study the structure and stability of line-driven winds using numerical hydrodynamic simulations. We calculate the radiation force from an explicit non-local solution of the radiation transfer equation, rather than a Sobolev approximation, without restricting the flow to one-dimensional symmetry. We find that the solutions that result have complex and highly variable structures, including dense condensations, which we compare with observed variable absorption features in the spectra of early-type stars.

Can planet formation resolve the dust budget crisis in high-redshift galaxies?

DHF gratefully acknowledges support from the ECOGAL project, grant agreement 291227, funded by the European Research Council under ERC-2011-ADG. K R acknowledges support from the European Research Council Starting Grant SEDmorph (P.I. V. Wild). HLG, LD and SM acknowledge support from the European Research Council (ERC) in the form of Consolidator Grant COSMICDUST (ERC-2014-CoG- 647939, PI HL Gomez). LD and SJM acknowledge support from European Research Council Advanced Investigator Grant COSMICISM, 321302.

IAU Office of Astronomy for Development: Task Force Children and School Education

The main mission of the IAU OAD Task Force on Children and School Education is to support the implementation of the pre-tertiary education part of the IAU Strategic Plan ‘Astronomy for Development’. In this presentation we will give an overview of the role and programme of the task force as well as a general discussion about the past, present and future IAU education activities and programmes.