Документ взят из кэша поисковой машины. Адрес оригинального документа : http://www.stsci.edu/hst/proposing/docs/exp_abstract-catalogs/Cycle22-Approved-Abstracts.pdf Дата изменения: Unknown Дата индексирования: Tue Apr 12 00:23:46 2016 Кодировка: Поисковые слова: magellan project

Cycle 22 Abstract Catalog (Based on Phase I Submissions) Proposal Category: Scientific Category: ID: Program Title: GO Solar System 13633 A Kuiper Belt Object for the New Horizons Mission

Principal Investigator: PI Institution:

John

Spencer

Southwest Research Institute

The Kuiper Belt is arguably the most important discovery in planetary science in decades. On behalf of the New Horizons (NH) mission, we propose to use WFC3 to identify KBO flyby targets for NH. This proposal will also significantly improve knowledge on two crucial scientific questions: the size-frequency distribution and the binary fraction of 30-50 km diameter KBOs, providing important constraints on disk accretion and fragmentation processes of interest to both solar system and extrasolar planet origins. STScI's Director has committed both 40 DD orbits and early implementation in summer 2014 to this GO effort. The 2002 Planetary Decadal Survey ranked Pluto-KBO exploration at the top of the NASA medium-scale mission queue and cited the KBO flyby as a fundamental mission objective. There is no prospect of a KBO flyby by any other mission than NH. Intensive ground-based searches for a flyby target since 2011 have been unsuccessful, and offer a <50% chance of success in 2014, likely leaving the KBO mission with no accessible targets. But owing to its small and stable PSF, and zero chance of weather loss of observing time, we estimate an ~94% chance of finding a targetable KBO with this proposed 2014 HST program. Hubble is the only highprobability means to rescue the exploration of the Kuiper Belt; no other NASA orbital asset can. A discovery in 2014 is required to achieve the needed one-year tracking arc for an 2015 spacecraft targeting maneuver; as described below, discovery delay to 2015 reduces the probability of detecting a KBO within the fuel budget of NH to <15% by groundbased techniques and <55% by HST

Proposal Category: Scientific Category: ID: Program Title:

GO Unresolved Stellar Populations and Galaxy 13639 Resolving Lyman-alpha Emission On Physical Scales < 270 pc at z > 4

Principal Investigator: PI Institution:

Matthew Harvard University

Bayliss

We propose ACS-WFC Ramp narrowband imaging of six strongly lensed Lyman-alpha Emitters (LAEs) at z > 4 that will spatially resolve the Lyman-alpha line emitting regions on scales < 270 pc. The best available observations (HST, Spitzer, 10m ground based telescopes) are unable to provide robust measurements of the structure of these galaxies from blank field studies, but strong gravitational lensing provides a unique opportunity to peer into the heart of young star forming galaxies at high redshift and address outstanding questions regarding their morphology and evolution. Strong lensing magnifies each of our target LAEs, increasing the effective spatial resolution of ACS-WFC such that the point spread function will correspond to physical scales < 270 parsecs within all six z > 4 galaxies. Additionally, the boost in flux due to gravitational lensing makes our proposed targets the brightest sources of their kind at these redshifts, in spite of the fact that they are intrinsically ~L* LAEs. The proposed observations will probe the

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signal-to-noise and spatial resolution comparable to studies of Lyman-alpha emitting galaxies in the z ~ 0.1 universe. The resulting data will bridge the gap between deep ground-based studies of blank field LAEs at high redshift, and detailed studies of low-redshift LAEs.

Proposal Category: Scientific Category: ID: Program Title:

GO Cool Stars 13640 A direct probe of cloud holes at the L/T transition

Principal Investigator: PI Institution:

Esther

Buenzli

Max-Planck-Institut fur Astronomie, Heidelberg

Understanding cloud formation, evolution and dispersal is one of the biggest challenges in the field of substellar atmospheres. At the transition from L to T type brown dwarfs, thick silicate and iron clouds disappear below the visible photosphere and the spectra are altered dramatically despite little change in effective temperature. Observed strengthening of the FeH band through the transition has indicated an opening of cloud holes rather than gradual sinking of the clouds. This view has been supported by the discovery of brown dwarfs with photometric variability attributed to patchy cloud cover. However, our recent spectral variability observations have complicated the picture because patchy cloud models with cloud holes currently cannot reproduce the color variations and spectral variability signatures. Whether this implies an absence of cloud holes (in contradiction to the interpretation of the observed strengthening of FeH) or is because models neglect other mechanisms that can affect the colors (eg temperature anomalies) remains unclear. Here, we propose WFC3/G102 spectral variability observations of the very nearby L/T transition benchmark binary Luhman 16AB, the only known variable brown dwarfs in a binary system. These observations target the FeH band. As the FeH molecule contains the cloud forming atom Fe, it is a direct tracer of the cloud holes. By comparing the variability amplitude in the FeH band with the surrounding continuum, as well as between the L and T component at different stages of cloud evolution, we will obtain direct evidence whether the formation of cloud holes is indeed the driving mechanism behind cloud dispersal at the L/T transition.

Proposal Category: Scientific Category: ID: Program Title:

GO Unresolved Stellar Populations and Galaxy 13641 A Detailed Dynamical And Morphological Study Of 5
Principal Investigator: PI Institution: 2

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We propose WFC3-IR imaging for a unique sample of 10 ~L* "normal" 55 from Keck and VLT along with the wealth of multi-wavelength data in the proposed COSMOS field ensure the physical properties and local environment of these sources is known. Immediate studies with the proposed WFC3-IR data include: 1) Measuring the rest-frame Ultraviolet (UV) spectral slopes to calibrate the infrared-excess - UV-slope (IRX-beta) relation which is an essential ingredient in estimating star formation rates at z>5 (e.g. Bouwens et al. 2012, Finkelstein et al. 2012), but is currently determined at z~0-2 and expected to strongly evolve at higher redshift (Meurer et al. 1999, Reddy et al. 2010,2012). 2) Compare quantitative morphologies with the ALMA dynamical measurements, constraining the formation mechanisms of these galaxies. 3) Significantly improve the spectra-energy distribution fits used to estimate stellar masses, which when combined with the dynamical mass estimates and atomic line data will test for biases in the mass estimates.

Proposal Category: Scientific Category: ID: Program Title:

GO Hot Stars 13642 The evolutionary link between low-mass X-ray binaries and millisecond radio pulsars

Principal Investigator: PI Institution:

Nathalie University of Michigan

Degenaar

Low-mass X-ray binaries (LMXBs) and millisecond radio pulsars (MSRPs) are two different manifestations of neutron stars in binary systems. They are thought to be evolutionary linked, but many questions about their connection remain. Recent discoveries have opened up a new vista to investigate the LMXB/MSRP link. The neutron star XSS J12270-4859 was recently observed to switch between the two different manifestations. Here, we propose to exploit the unique UV capabilities of the HST to search for the presence of a quiescent accretion disk and to test if the neutron star is hot. This will give insight into its accretion history and the mechanism driving its metamorphosis, which will have direct implications for our understanding of the LMXB/MSRP evolutionary link.

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Cycle 22 Abstract Catalog (Based on Phase I Submissions) Proposal Category: Scientific Category: ID: Program Title: GO ISM and Circumstellar Matter 13643 Imaging the tenuous dusty atmosphere of edge-on protoplanetary disks

Principal Investigator: PI Institution:

Gaspard

Duchene

University of California - Berkeley

In a successful Cycle 19 survey for edge-on protoplanetary disks, we have discovered that some, but not all, protoplanetary disks present a tenuous atmosphere detected in scattered light, thus containing dust grains, located well above the optically thick disk surface. This atmosphere could be direct evidence for the super-heated region above the disk surface due to direct illumination from the central star or for a disk wind that carries along the smallest dust grains from the disk surface. Here we propose to obtain the first F475W images of a sample of six edge-on protoplanetary disks, four of which were discovered in our Cycle 19 survey, in order to constrain the characteristic grain size in the disk atmosphere and establish whether the presence of this atmosphere correlates with other disk properties. With our carefully selected sample, we will correlate the properties of the disk atmosphere with other properties of the system, such as presence of a collimated jet, dust settling and grain growth, thus providing a first empirical analysis of the nature of this phenomenon.

Proposal Category: Scientific Category: ID: Program Title:

GO Cosmology 13644 CIII] Emission in z=5.7 Galaxies: A Pathfinder for Galaxy Spectroscopy in the Reionization Era Xiaohui University of Arizona Fan

Principal Investigator: PI Institution:

The last few years has witnessed a rapid increase in the detections of galaxies at z>7, at the end of the reionization era. However, as a result of the increasing attenuation of Ly alpha emission by the partially neutral IGM at this redshift, it is becoming clear that the traditional means of redshift confirmation is bound for limited success; this presents a major challenge to galaxy spectroscopy as we probe deeper into the reionization era with JWST and ELTs. Through our survey of reionization-era analog galaxies at z~2, we find that low metallicity, low luminosity galaxies exhibit strong CIII] 1909 nebular emission lines. If, as is expected, CIII] remains strong at high redshift, the line can be used as a powerful alternative to Ly alpha in spectroscopy of reionization-era galaxies. To explore this possibility, we will carry out deep HST WFC3/IR F128N narrow-band imaging of a sample of 8 galaxies at z=5.7 in two fields. At this redshift, the CIII] line is fortuitously located within the F128N passband, allowing detection of CIII] in this sample of spectroscopically

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confirmed galaxies, reaching a flux limit beyond what is possible with current ground-based observations. Combining the F128N narrow-band imaging with broad-band observations, we will reliably measure the CIII] flux for the brighter objects in our sample (J<~26), and measure or strongly constrain the stacked CIII] flux for fainter objects (J~27). This program will provide the first statistical sample of CIII] emission in galaxies close to the end of reionization. Success in this venture would usher in a new era of redshift confirmation at z>7, guiding the strategy of such programs on future major facilities.

Proposal Category: Scientific Category: ID: Program Title:

GO AGN/Quasars 13645 Galactic Environment of A Twenty-Billion Solar-Mass Black Hole at the End of Reionization Xiaohui University of Arizona Fan

Principal Investigator: PI Institution:

When did the first supermassive black holes (SMBHs) appear in the universe? How do they co-evolve with and impact their galactic environment? We propose to carry out deep HST ACS and WFC/IR imaging of a newly discovered ultraluminous quasar at z=6.30. At about 10 times brighter than an average SDSS z~6 quasar, this object is the most luminous quasar yet known at z>5.5 and is powered by a SMBH with an estimated mass of 20 billion M_sun, comparable to the most massive SMBHs found in the local universe. It is among the most massive systems in the observable early universe and likely resides in the densest and most biased environment at the end of cosmic reionization. Our WFC/IR J and H band observations will reveal the rest-frame UV emission in the quasar host galaxy, directly probing the coeval star formation in quasar host when the SMBH is accreting at the highest rate. Deep HST images will be used to rule out or confirm lensing magnification and to search for signatures of major merger activity. We will use the ACS i and z band imaging, combined with WFC/IR imaging, to select young star forming galaxies in the quasar environment and to study whether this ultra-luminous quasar lives in a significant galaxy overdensity, or whether early reionization has suppressed galaxy formation in the quasar environment. The HST observations will provide key insight into the formation and evolution of the earliest 10^10 M_sun BH systems in the universe.

Proposal Category: Scientific Category: ID: Program Title:

GO Hot Stars 13646 Understanding the Progenitor Systems, Explosion Mechanisms, and Cosmological Utility of Type Ia Supernovae Ryan Foley

Principal Investigator:

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Despite using Type Ia supernovae (SN Ia) to precisely measure cosmological parameters, we still do not know basic facts about the progenitor systems and explosions. Theory suggests that SN Ia progenitor metallicity is correlated with its peak luminosity, but not its light-curve shape. As a result, this effect should lead to an increased Hubble scatter, reducing the precision with which we measure distances. If the average progenitor metallicity changes with redshift, cosmological measurements could be biased. Models also indicate that changing the progenitor metallicity will have little effect on the appearance of optical SN data, but significantly change UV spectra. These data can only be obtained with HST. We recently published the first detection of 2 SN Ia with different progenitor metallicities. These "twin" SN had nearly identical optical spectra and light-curve shapes, but different UV spectra and peak luminosities, consistent with the models. We now must increase the sample of SN Ia with UV spectral time series to investigate the impact of metallicity on SN properties. To do this, we plan to obtain UV spectral time series of 3 SN Ia, nearly doubling the sample. UV observations are critical to the understanding of SN Ia explosions and progenitors. This is our best opportunity to further our understanding of SN Ia while directly improving the utility of SN Ia for cosmology. Using parallel observations, we will obtain Cepheid distances to a subset of the SN for free, providing precise SN luminosities and a better measurement of the Hubble constant. The UV Initiative is an excellent opportunity for HST to address significant questions in SN physics and cosmology.

Proposal Category: Scientific Category: ID: Program Title:

GO Cosmology 13647 Testing the Standardizability of Type Ia Supernovae with the Cepheid Distance of a Twin Supernova Ryan Foley

Principal Investigator: PI Institution:

University of Illinois at Urbana - Champaign

Having nearly identical optical light-curve shapes, colors, and spectra, SN 2011by and 2011fe are "twin" Type Ia supernovae (SN Ia). As such, these "standardizable candles" should have identical luminosities. But using independent distance measurements to these SN, their peak luminosity differs by 0.6 mag --- significantly larger than the typical scatter amongst all SN Ia. Differences in their UV spectra indicate that the SN have different metallicities, which could account for the luminosity difference. On the other hand, the distance to SN 2011by, from a Tully-Fisher measurement, may be wrong. We propose to measure a Cepheid distance to SN 2011by to determine if metallicity or an imprecise measurement is causing this large difference. The implications are far reaching for SN cosmology. If the current distance is correct, changing progenitor metallicity could cause large distance biases with redshift. If the distance is revised to bring SN 2011by in line with SN 2011fe, we will infer that metallicity differences are not a large bias for SN cosmology. In the latter case, these data will also provide an additional SN with which we can measure the Hubble constant. Since the number of SN calibrators (only 8 published) limits the precision of our measurement of the Hubble constant, these observations can have a large impact on this measurement.

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Cycle 22 Abstract Catalog (Based on Phase I Submissions) Proposal Category: Scientific Category: ID: Program Title: GO Hot Stars 13648 Uncovering the Putative B-Star Binary Companion of the SN 1993J Progenitor

Principal Investigator: PI Institution:

Ori

Fox

University of California - Berkeley

The stripped-envelope Type IIb supernova (SN IIb) is a unique subclass of core-collapse explosions that result when a massive star loses most, but not all, of its outer envelope. Theoretical models suggest progenitor systems consist of low-mass stars that lose their envelopes during mass transfer to a binary companion, which becomes UV bright in the process. Although four stripped-envelope supernovae have progenitor stars identified in pre-explosion images, not a single progenitor companion star has been directly detected to date. In other words, the Type IIb progenitor system remains observationally unconfirmed. The nearby Type IIb SN 1993J in M81, at a distance of only 3.6 Mpc, offers one of the best opportunities to detect the putative companion and test the progenitor model. Indeed, evidence has been mounting over the past decade for a hot companion, but the dominating SN flux and contamination from nearby stars has made a confirmation difficult. In 2012, our team obtained HST/COS spectra and detected a far-UV (FUV) excess flux consistent with a hot B-star. This spectrum, however, is limited by a low signal-to-noise ratio and poor spatial resolution. Now that the SN has sufficiently faded, we propose FUV and NUV imaging of SN 1993J and the surrounding stars to disentangle the source of the FUV excess flux once and for all. Coinciding with Cycle 22's UV initiative, we can shed light on the binary nature of Type IIb progenitors in just 3 orbits.

Proposal Category: Scientific Category: ID: Program Title:

GO Hot Stars 13649 UV Spectroscopic Signatures from Type Ia Supernovae Strongly Interacting with a Circumstellar Medium Ori Fox

Principal Investigator: PI Institution:

University of California - Berkeley

Type Ia supernovae (SNe Ia) are well-known for their use as precise cosmological distance indicators due to a standardizable peak luminosity resulting from a thermonuclear explosion. A growing subset of SNe Ia, however, show evidence for interaction with a dense circumstellar medium during the first year post-explosion, and sometimes longer (SNe Ia-CSM). The origin of this dense CSM is unknown and suggests either a) the less typical single-degenerate progenitor scenario must be considered or b) the exploding star was not a thermonuclear explosion of a white dwarf at all (i.e., core-collapse). The ultraviolet (UV) offers a unique opportunity to determine the true nature of the SNe Ia-CSM subclass. Unlike optical wavelengths, which can be quite ambiguous, the UV has distinguishing features due to its sensitivity to the composition of the optically thin ejecta that are illuminated by X-rays generated by shock interaction. Yet not a single UV spectrum exists for this subclass. Here we propose a non-disruptive ToO with HST/STIS to obtain 3

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epochs (5 orbits the SN explosion late-time heating regarding both th each) of UV spectra of a SN Ia-CSM within 100 Mpc. This mechanisms, but also trace CSM interaction, constrain the mechanisms of warm dust. Coinciding with Cycle 22's UV e progenitor and explosion characteristics of the SN Ia-CSM program will not only distinguish between progenitor mass loss history, and identify Initiative, this program offers new insights subclass.

Proposal Category: Scientific Category: ID: Program Title:

GO Extra-Solar Planets 13650 The MUSCLES Treasury Survey: Measurements of the Ultraviolet Spectral Characteristics of Low-mass Exoplanetary Systems Kevin France

Principal Investigator: PI Institution:

University of Colorado at Boulder

It has recently been discovered that 10 - 50% of M dwarfs host Earth-size planets in their habitable zones. Furthermore, the nearest potentially habitable super-Earths orbit M dwarfs, meaning that these systems likely represent our best chance to discover habitable worlds in the coming decade. The ultraviolet (UV) spectrum incident upon Earthlike planets drives the dissociation of water and CO2, the production of O2 and ozone, and may determine their ultimate habitability. At present, we lack the observational and theoretical basis to predict the energetic radiation spectrum (X-ray through UV) of an M dwarf. UV variability of low-mass exoplanet host stars, in particular the possibly sterilizing effect of flare activity, is almost completely unexplored observationally. This proposal aims to acquire the critical UV observations of low-mass host stars now, providing a treasury database for studies of exemplary nearby exoplanetary systems and potentially habitable worlds not yet discovered. Building on our successful pilot program of spectrally and temporally resolved UV radiation fields, we propose the MUSCLES Treasury Survey: a UV survey of nearby low-mass exoplanetary host stars. Using HST-COS and STIS, we will observe the 1150 - 5700A fluxes, reconstruct the important Ly-alpha emission lines, and use these data to estimate the extreme-UV (200 - 912A) irradiances incident upon exoplanetary atmospheres. The UV data will be complemented with contemporaneous X-ray and ground-based observations as well as new M dwarf atmosphere models to constrain atmospheric heating rates and provide a baseline for long-term ground-based studies of these systems.

Proposal Category: Scientific Category: ID: Program Title:

GO AGN/Quasars 13651 Disentangling Signatures of Ultra-high-energy Cosmic Rays from a Unique Gammaray Blazar Amy Furniss

Principal Investigator: PI Institution: 8

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Blazars have been postulated as possible progenitors of ultra-high-energy cosmic rays (UHECRs; E>1 PeV) for decades. This is particularly compelling in the case of blazars observed as TeV gamma-ray sources, since acceleration of particles to extreme energies must take place there. Unfortunately, convincing evidence supporting this theory has yet to be collected, mainly due to lack of firm measurements of blazar distances. Leveraging a novel technique that we successfully used to robustly pin-down redshifts in four blazars via absorption spectroscopy, we propose HST/COS observations of B2 1215+30, a blazar with the unique potential to address the validity of blazars as acceleration sources of UHECRs. These observations will provide firm limits on the distance to B2 1215+30, which will be used in conjunction with archival observations in the very high energy (VHE; E>100 GeV) band to enable a detailed study of the interaction of UHECRs with the lower-energy extragalactic photon fields along the line of sight between B2 1215 +30 and the Earth.

Proposal Category: Scientific Category: ID: Program Title:

SNAP Extra-Solar Planets 13652 The frequency and chemical composition of rocky planetary debris around young white dwarfs: Plugging the last gaps Boris Gaensicke

Principal Investigator: PI Institution:

The University of Warwick
stars into white dwarfs (WDs). In the WD remnant of the Sun, and debris was detected in ~20% of balance makes the ground-based

Many planetary systems will survive the post main-sequence evolution of their host the solar system, Mars, the asteroid belt, and the outer planets will eventually orbit many WDs are known to have remnants of planetary systems. Historically, planetary WDs with cooling ages >0.5Gyr from Ca K detections. However, the Ca II ionisation detection of planetary debris at younger, hotter WDs impossible.

We have carried out a very successful Cycle 18/19 COS snapshot survey of 100 WDs with cooling ages of 20-200Myr, and detect metal pollution in up to 50% of all targets via the strong Si resonance lines. This survey also showed that terrestrial material is common around A-stars, that rocky exo-planetary bodies display a similar variety in abundances as the meteorites in our solar system, and that water-rich Ceres-like asteroids still exist in evolved planetary systems. We propose to close the last gaps in the statistics of evolved planetary systems: an extension of our snapshot survey to cooling ages of 5-25Myr and 100-300Myr. Our orbital integrations suggest that mass-loss during the AGB phase can stirr up instabilities leading to planet-planet collisions, which should be most frequent during the first 10Myr, and the proposed observations will unambiguously test these predictions. In addition, the extended sample will improve the statistics on the formation of planetary systems as a function of host star mass, and build up a deeper insight into the abundances of rocky exo-planetary material that will guide models of terrestrial planet formation

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Cycle 22 Abstract Catalog (Based on Phase I Submissions) Proposal Category: Scientific Category: ID: Program Title: GO Extra-Solar Planets 13653 Elementary Abundances of Planetary Systems

Principal Investigator: PI Institution:

Caitlin University of Arizona

Griffith

Close-orbiting Hot Jupiter exoplanets were not predicted because the ices needed to build their large cores would have accreted in the outer stellar system where temperatures are cool enough for ices to condense. Their existence suggests more substantial planet migration than indicated in the Solar System, or perhaps different formation mechanisms. To probe the formation environment of Hot Jupiters, we propose measurements of the elemental abundances of oxygen and carbon, which derive from icy (H2O, C02 and CO) planetismals that condensed in different parts of the disk. To determine the water abundance at the precision needed to detect ice-derived material in Jupiter's atmosphere, we propose a coordinated ground-based and space-based study. We target the exoplanet XO-2b, which has an ideal reference star (the host star's binary companion of similar stellar type and brightness), allowing us to remove atmospheric effects from the ground-based measurements. We propose to measure XO-2b's water bands with HST/WFC3 1.1-1.7 micron spectra, which enables a retrieval of CO from the already measured Spitzer transit and eclipse photometry. Simultaneous Gemini optical measurements constrain XO-2b's 10-bar radius and the cloud coverage, which allow us to constrain the degenerate solution set and decrease uncertainties in retrieved water abundances from current values of a factor of 100 to our expected uncertainty of a factor of 3 in the derived abundance. The aim of this study is to derive strategies for measuring accurate exoplanetary compositions, as needed to pursue statistically significant studies.

Proposal Category: Scientific Category: ID: Program Title:

GO ISM in External Galaxies 13654 Ultraviolet Spectroscopy of the Extended Lyman Alpha Reference Sample

Principal Investigator: PI Institution:

Matthew Stockholm University

Hayes

The importance of the Lyman alpha (Lya) emission line for high-z galaxy studies cannot be overstated. Tens of thousands of galaxies have been found and confirmed through Lya, and in the next decade the samples will increase 100-fold. Yet Lya is a resonance line, and transfer effects may bias surveys in complicated and unknown ways if fundamental relations between Lya observables and physical properties are not established. This requires large samples and comprehensive multi-wavelength data sets. The Extended Lyman alpha Reference Sample is a sample of 28 starforming galaxies, complete with 8-band HST imaging, 21 cm observations of HI gas, and a plethora of other data: it will provide the gold-standard study of Lya astrophysics in extragalactic laboratories. Currently eLARS includes no data from which to measure the Lya line profile or the covering/kinematics of the ISM - properties ranked among the most crucial for Lya transfer.

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The proposed COS spectra will measure ~8 ISM absorption lines, Ly-alpha itself, and an array of stellar features. From this we will: 1. determine the covering and kinematics of the neutral and ionized ISM - the material through which Lya transfers 2. resolve the Lya emission/absorption and model the properties of the HI medium 3. quantify of mechanical feedback from massive stars and supernovae 4. enhance the accuracy and ensure maximal return from ACS Lya imaging With large-scale galaxy surveys now beginning, eLARS spectroscopy will provide a vital interpretive dataset for the coming decades when no UV platforms are available. It adheres perfectly to the philosophy of the UV initiative.

Proposal Category: Scientific Category: ID: Program Title:

GO ISM in External Galaxies 13655 How Lyman alpha bites/beats the dust

Principal Investigator: PI Institution:

Matthew Stockholm University

Hayes

The bulk of high redshift star formation occurs in IR-bright objects. At similar epochs the de facto spectroscopic tracer of galaxies is the Lyman-alpha line, which is used almost ubiquitously with a diverse range of applications in galaxy evolution. Ly-alpha is also very sensitive to dust absorption, however, and a challenging emergent result of recent years is that an overwhelming fraction of IR-bright galaxies are also luminous Ly-alpha emitters. How is this possible given the mammoth dust contents? We will take advantage of the unique capabilities of HST and the Cycle 22 UV initiative to find out. Ly-alpha observations are infamously difficult to interpret because of the resonant nature of the transition. This has motivated detailed studies of nearby galaxies with space-based platforms, that have aided in unleash