arXiv subjects

Haley Gomez

Publications and source records attributed to Haley Gomez.

16 recordsLinked to original sources

arXiv2023

Newly Formed Dust within the Circumstellar Environment of SNIa-CSM 2018evt

Dust associated with various stellar sources in galaxies at all cosmic epochs remains a controversial topic, particularly whether supernovae (SNe) play an important role in dust production. We report evidence of dust formation in the cold, dense shell behind the ejecta-circumstellar medium (CSM) interaction in the Type Ia-CSM SN 2018evt three years after the explosion, characterized by a rise in the mid-infrared (MIR) emission accompanied by an accelerated decline in the optical radiation of the SN. Such a dust-formation picture is also corroborated by the concurrent evolution of the profiles of the Ha emission line. Our model suggests enhanced CSM dust concentration at increasing distances from the SN as compared to what can be expected from the density profile of the mass loss from a steady stellar wind. By the time of the last MIR observations at day +1041, a total amount of 1.2+-0.2x10^{-2} Msun of new dust has been formed by SN 2018evt, making SN 2018evt one of the most prolific dust factories among SNe with evidence of dust formation. The unprecedented witness of the intense production procedure of dust may shed light on the perceptions of dust formation in cosmic history.

astro-ph.HE↗

arXiv2023

Metal Factories in the Early Universe

We have measured the mass of metals in the molecular gas in 13 submillimetre galaxies at z~4 in which the gas, based on previous observations, lies in a cold rotating disk. We measured the metal masses using either the submillimetre line or continuum emission from three tracers of the overall metal content - carbon atoms, carbon monoxide molecules and dust grains - using the first simultaneous calibration of all three tracers (Dunne et al. 2022). We obtain very similar mass estimates from the different tracers, which are similar to the entire metal content of a present-day massive early-type galaxy. We used the dynamical masses of these galaxies to set an upper limit on the mass of the molecular gas in each galaxy, allowing us to set a lower limit on the metal abundance in the gas, finding values for many of the galaxies well above the solar value. We use chemical evolution models to show that such high metal masses and abundances are what is expected shortly after the formation of a galaxy for a top-heavy IMF. We suggest a scenario for galaxy evolution in which massive galaxies reach a high metal abundance during their formation phase, which is then gradually reduced by dry mergers with lower mass galaxies. We use the chemical-evolution models to show that the metals in the outflows from massive early-type galaxies in their formation phase can quantitatively explain the long-standing puzzle that approximately 75% of the metals in clusters of galaxies is in the intracluster gas rather than in the galaxies.

astro-ph.GA↗

arXiv2020

A Complete Catalogue of Dusty Supernova Remnants

We search for far-infrared (FIR) counterparts of known supernova remnants (SNRs) in the Galactic plane (360 degrees in longitude and b = +/- 1 deg ) at 70 - 500 micron with Herschel. We detect dust signatures in 39 SNRs out of 190, made up of 13 core-collapse supernovae (CCSNe), including 4 Pulsar Wind Nebulae (PWNe), and 2 Type Ia SNe. A further 24 FIR detected SNRs have unknown types. We confirm the FIR detection of ejecta dust within G350.1-0.3, adding to the known sample of ~10 SNRs containing ejecta dust. We discover dust features at the location of a radio core at the centre of G351.2+0.1, indicating FIR emission coincident with a possible Crab-like compact object, with dust temperature and mass of Td = 45.8 K and Md = 0.18 solar mass, similar to the PWN G54.1+0.3. We show that the detection rate is higher among young SNRs. We produce dust temperature maps of 11 SNRs and mass maps of those with distance estimates, finding dust at temperatures 15 < Td < 40 K. If the dust is heated by shock interactions the shocked gas must be relatively cool and/or have a low density to explain the observed low grain temperatures.

astro-ph.GA↗

arXiv2019

The Dust in M31

We have analysed Herschel observations of M31, using the PPMAP procedure. The resolution of PPMAP images is sufficient (31 pc on M31) that we can analyse far-IR dust emission on the scale of Giant Molecular Clouds. By comparing PPMAP estimates of the far-IR emission optical depth at 300 microns (tau_300), and the near-IR extinction optical depth at 1.1 microns (tau_1.1) obtained from the reddening of RGB stars, we show that the ratio R_OBS.tau = tau_1.1/tau_300 falls in the range 500 to 1500. Such low values are incompatible with many commonly used theoretical dust models, which predict values of R_MODEL.kappa = kappa_1.1/kappa_300 (where kappa is the dust opacity coefficient) in the range 2500 to 4000. That is, unless a large fraction, at least 60%, of the dust emitting at 300 microns is in such compact sources that they are unlikely to intercept the lines of sight to a distributed population like RGB stars. This is not a new result: variants obtained using different observations and/or different wavelengths have already been reported by other studies. We present two analytic arguments for why it is unlikely that at least 60% of the emitting dust is in sufficiently compact sources. Therefore it may be necessary to explore the possibility that the discrepancy between observed values of R_OBS.tau and theoretical values of R_MODEL.kappa is due to limitations in existing dust models. PPMAP also allows us to derive optical-depth weighted mean values for the emissivity index, beta = - dln(kappa_lambda)/dln(lambda), and the dust temperature, T, denoted betabar and Tbar. We show that, in M31, R_OBS.tau is anti-correlated with betabar according to R_OBS.tau = 2042(+/-24)-557(+/-10)betabar. If confirmed, this provides a challenging constraint on the nature of interstellar dust in M31.

astro-ph.GA↗

arXiv2019

Astro2020: Unleashing the Potential of Dust Emission as a Window onto Galaxy Evolution

We present the severe, systematic uncertainties currently facing our understanding of dust emission, which stymie our ability to truly exploit dust as a tool for studying galaxy evolution. We propose a program of study to tackle these uncertainties, describe the necessary facilities, and discuss the potential science gains that will result. This white paper was submitted to the US National Academies' Astro2020 Decadal Survey on Astronomy and Astrophysics.

astro-ph.GA↗

arXiv2019

The ALMA Fornax Cluster Survey I: stirring and stripping of the molecular gas in cluster galaxies

We present the first results of the ALMA Fornax Cluster Survey (AlFoCS): a complete ALMA survey of all members of the Fornax galaxy cluster that were detected in HI or in the far infrared with Herschel. The sample consists of a wide variety of galaxy types, ranging from giant ellipticals to spiral galaxies and dwarfs, located in all (projected) areas of the cluster. It spans a mass range of 10^(~8.5 - 11) M_Sun. The CO(1-0) line was targeted as a tracer for the cold molecular gas, along with the associated 3 mm continuum. CO was detected in 15 of the 30 galaxies observed. All 8 detected galaxies with stellar masses below 3x10^9 M_Sun have disturbed molecular gas reservoirs, only 6 galaxies are regular/undisturbed. This implies that Fornax is still a very active environment, having a significant impact on its members. Both detections and non-detections occur at all projected locations in the cluster. Based on visual inspection, and the detection of molecular gas tails in alignment with the direction of the cluster centre, in some cases ram pressure stripping is a possible candidate for disturbing the molecular gas morphologies and kinematics. Derived gas fractions in almost all galaxies are lower than expected for field objects with the same mass, especially for the galaxies with disturbed molecular gas, with differences of sometimes more than an order of magnitude. The detection of these disturbed molecular gas reservoirs reveals the importance of the cluster environment for even the tightly bound molecular gas phase.

astro-ph.GA↗

arXiv2018

A Catalogue of Galactic Supernova Remnants in the far-infrared: revealing ejecta dust in pulsar wind nebulae

We search for far-infrared (FIR) counterparts of known supernova remnants (SNRs) in the Galactic plane (10 deg <| l |< 60 deg) at 70-500 micron using the Herschel Infrared Galactic Plane Survey (Hi-GAL). Of 71 sources studied, we find that 29 (41 per cent) SNRs have a clear FIR detection of dust emission associated with the SNR. Dust from 8 of these is in the central region, and 4 indicate pulsar wind nebulae (PWNe) heated ejecta dust. A further 23 have dust emission in the outer shell structures which is potentially related to swept up material. Many Galactic SNe have dust signatures but we are biased towards detecting ejecta dust in young remnants and those with a heating source (shock or PWN). We estimate the dust temperature and mass contained within three PWNe, G11.2-0.3, G21.5-0.9, and G29.7-0.3 using modified blackbody fits. To more rigorously analyse the dust properties at various temperatures and dust emissivity index beta, we use point process mapping (PPMAP). We find significant quantities of cool dust (at 20-40 K) with dust masses of Md = 0.34 +/- 0.14 solar mass, Md = 0.29 +/- 0.08 solar mass, and Md = 0.51 +/- 0.13 solar mass for G11.2-0.3, G21.5-0.9, and G29.7-0.3 respectively. We derive the dust emissivity index for the PWN ejecta dust in G21.5-0.3 to be beta = 1.4 +/- 0.5 compared to dust in the surrounding medium where beta = 1.8 +/- 0.1.

astro-ph.GA↗

arXiv2017

The Herschel-ATLAS Data Release 2, Paper I. Submillimeter and Far-infrared Images of the South and North Galactic Poles: The Largest Herschel Survey of the Extragalactic Sky

We present the largest submillimeter images that have been made of the extragalactic sky. The Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS) is a survey of 660 deg$^2$ with the PACS and SPIRE cameras in five photometric bands: 100, 160, 250, 350, and 500μm. In this paper we present the images from our two largest fields which account for ~75% of the survey. The first field is 180.1 deg$^2$ in size centered on the North Galactic Pole (NGP) and the second field is 317.6 deg$^2$ in size centered on the South Galactic Pole. The NGP field serendipitously contains the Coma cluster. Over most (~80%) of the images, the pixel noise, including both instrumental noise and confusion noise, is approximately 3.6, and 3.5 mJy/pix at 100 and 160μm, and 11.0, 11.1 and 12.3 mJy/beam at 250, 350 and 500μm, respectively, but reaches lower values in some parts of the images. If a matched filter is applied to optimize point-source detection, our total 1σ map sensitivity is 5.7, 6.0, and 7.3 mJy at 250, 350, and 500μm, respectively. We describe the results of an investigation of the noise properties of the images. We make the most precise estimate of confusion in SPIRE maps to date finding values of 3.12+/-0.07, 4.13+/-0.02 and 4.45+/-0.04 mJy/beam at 250, 350, and 500μm in our un-convolved maps. For PACS we find an estimate of the confusion noise in our fast-parallel observations of 4.23 and 4.62 mJy/beam at 100 and 160μm. Finally, we give recipes for using these images to carry out photometry, both for unresolved and extended sources.

astro-ph.GA↗

arXiv2017

GAMA/G10-COSMOS/3D-HST: The 0<z<5 cosmic star-formation history, stellar- and dust-mass densities

We use the energy-balance code MAGPHYS to determine stellar and dust masses, and dust corrected star-formation rates for over 200,000 GAMA galaxies, 170,000 G10-COSMOS galaxies and 200,000 3D-HST galaxies. Our values agree well with previously reported measurements and constitute a representative and homogeneous dataset spanning a broad range in stellar mass (10^8---10^12 Msol), dust mass (10^6---10^9 Msol), and star-formation rates (0.01---100 Msol per yr), and over a broad redshift range (0.0 < z < 5.0). We combine these data to measure the cosmic star-formation history (CSFH), the stellar-mass density (SMD), and the dust-mass density (DMD) over a 12 Gyr timeline. The data mostly agree with previous estimates, where they exist, and provide a quasi-homogeneous dataset using consistent mass and star-formation estimators with consistent underlying assumptions over the full time range. As a consequence our formal errors are significantly reduced when compared to the historic literature. Integrating our cosmic star-formation history we precisely reproduce the stellar-mass density with an ISM replenishment factor of 0.50 +/- 0.07, consistent with our choice of Chabrier IMF plus some modest amount of stripped stellar mass. Exploring the cosmic dust density evolution, we find a gradual increase in dust density with lookback time. We build a simple phenomenological model from the CSFH to account for the dust mass evolution, and infer two key conclusions: (1) For every unit of stellar mass which is formed 0.0065---0.004 units of dust mass is also formed; (2) Over the history of the Universe approximately 90 to 95 per cent of all dust formed has been destroyed and/or ejected.

astro-ph.GA↗

arXiv2015

BFORE: The B-mode Foreground Experiment

The B-mode Foreground Experiment (BFORE) is a proposed NASA balloon project designed to make optimal use of the sub-orbital platform by concentrating on three dust foreground bands (270, 350, and 600 GHz) that complement ground-based cosmic microwave background (CMB) programs. BFORE will survey ~1/4 of the sky with 1.7 - 3.7 arcminute resolution, enabling precise characterization of the Galactic dust that now limits constraints on inflation from CMB B-mode polarization measurements. In addition, BFORE's combination of frequency coverage, large survey area, and angular resolution enables science far beyond the critical goal of measuring foregrounds. BFORE will constrain the velocities of thousands of galaxy clusters, provide a new window on the cosmic infrared background, and probe magnetic fields in the interstellar medium. We review the BFORE science case, timeline, and instrument design, which is based on a compact off-axis telescope coupled to >10,000 superconducting detectors.

astro-ph.IM↗

arXiv2015

H-ATLAS/GAMA: Quantifying the Morphological Evolution of the Galaxy Population Using Cosmic Calorimetry

Using results from the Herschel Astrophysical Terrahertz Large-Area Survey and the Galaxy and Mass Assembly project, we show that, for galaxy masses above approximately 1.0e8 solar masses, 51% of the stellar mass-density in the local Universe is in early-type galaxies (ETGs: Sersic n > 2.5) while 89% of the rate of production of stellar mass-density is occurring in late-type galaxies (LTGs: Sersic n < 2.5). From this zero-redshift benchmark, we have used a calorimetric technique to quantify the importance of the morphological transformation of galaxies over the history of the Universe. The extragalactic background radiation contains all the energy generated by nuclear fusion in stars since the Big Bang. By resolving this background radiation into individual galaxies using the deepest far-infrared survey with the Herschel Space Observatory and a deep near-infrared/optical survey with the Hubble Space Telescope (HST), and using measurements of the Sersic index of these galaxies derived from the HST images, we estimate that approximately 83% of the stellar mass-density formed over the history of the Universe occurred in LTGs. The difference between this and the fraction of the stellar mass-density that is in LTGs today implies there must have been a major transformation of LTGs into ETGs after the formation of most of the stars.

astro-ph.GA↗

arXiv2012

Nucleosynthetic Layers in the Shocked Ejecta of Cassiopeia A

We present a 3-dimensional analysis of the supernova remnant Cassiopeia A using high resolution spectra from the Spitzer Space Telescope. We observe supernova ejecta both immediately before and during the shock-ejecta interaction. We determine that the reverse shock of the remnant is spherical to within 7%, although the center of this sphere is offset from the geometric center of the remnant by 810 km/s. We determine that the velocity width of the nucleosynthetic layers is approximately 1000 km/s over 4000 square arcsecond regions, although the velocity width of a layer along any individual line of sight is <250 km/s. Si and O, which come from different nucleosynthetic layers in the progenitor star, are observed to be coincident in velocity space in some directions, but segregated by up to approximately 500 km/s in other directions. We compare these observations of the nucleosynthetic layers to predictions from supernova explosion models in an attempt to constrain such models. Finally, we observe small-scale, corrugated velocity structures that are likely caused during the supernova explosion itself, rather than hundreds of years later by dynamical instabilities at the remnant's reverse shock.

astro-ph.SR↗

arXiv2012

Can dust emission be used to map the interstellar medium in high-redshift galaxies? Results from the Herschel Reference Survey

It has often been suggested that an alternative to the standard CO/21-cm method for estimating the mass of the interstellar medium (ISM) in a galaxy might be to estimate the mass of the ISM from the continuum dust emission. In this paper, we investigate the potential of this technique using Herschel observations of ten galaxies in the Herschel Reference Survey and in the Herschel Virgo Cluster Survey. We show that the emission detected by Herschel is mostly from dust that has a temperature and emissivity index similar to that of dust in the local ISM in our galaxy, with the temperature generally increasing towards the centre of each galaxy. We calibrate the dust method using the CO and 21-cm observations to provide an independent estimate of the mass of hydrogen in each galaxy, solving the problem of the uncertain `X factor' for the molecular gas by minimizing the dispersion in the ratio of the masses estimated using the two methods. With the calibration for the dust method and the estimate of the X-factor produced in this way, the dispersion in the ratio of the two gas masses is 30%, which gives an upper limit on the fundamental accuracy of the dust method. The calibration we obtain for the dust method is very similar to an independent Herschel measurement for M31 and to the calibration for the Milky Way from Planck measurements.

astro-ph.CO↗

arXiv2010

The Three-Dimensional Structure of Cassiopeia A

We used the Spitzer Space Telescope's Infrared Spectrograph to map nearly the entire extent of Cassiopeia A between 5-40 micron. Using infrared and Chandra X-ray Doppler velocity measurements, along with the locations of optical ejecta beyond the forward shock, we constructed a 3-D model of the remnant. The structure of Cas A can be characterized into a spherical component, a tilted thick disk, and multiple ejecta jets/pistons and optical fast-moving knots all populating the thick disk plane. The Bright Ring in Cas A identifies the intersection between the thick plane/pistons and a roughly spherical reverse shock. The ejecta pistons indicate a radial velocity gradient in the explosion. Some ejecta pistons are bipolar with oppositely-directed flows about the expansion center while some ejecta pistons show no such symmetry. Some ejecta pistons appear to maintain the integrity of the nuclear burning layers while others appear to have punched through the outer layers. The ejecta pistons indicate a radial velocity gradient in the explosion. In 3-D, the Fe jet in the southeast occupies a "hole" in the Si-group emission and does not represent "overturning", as previously thought. Although interaction with the circumstellar medium affects the detailed appearance of the remnant and may affect the visibility of the southeast Fe jet, the bulk of the symmetries and asymmetries in Cas A are intrinsic to the explosion.

astro-ph.GA↗

arXiv2010

The Three-Dimensional Structure of Interior Ejecta in Cassiopeia A at High Spectral Resolution

We used the Spitzer Space Telescope's Infrared Spectrograph to create a high resolution spectral map of the central region of the Cassiopeia A supernova remnant, allowing us to make a Doppler reconstruction of its 3D structure. The ejecta responsible for this emission have not yet encountered the remnant's reverse shock or the circumstellar medium, making it an ideal laboratory for exploring the dynamics of the supernova explosion itself. We observe that the O, Si, and S ejecta can form both sheet-like structures as well as filaments. Si and O, which come from different nucleosynthetic layers of the star, are observed to be coincident in velocity space in some regions, and separated by 500 km/s or more in others. Ejecta traveling toward us are, on average, ~900 km/s slower than the material traveling away from us. We compare our observations to recent supernova explosion models and find that no single model can simultaneously reproduce all the observed features. However, models of different supernova explosions can collectively produce the observed geometries and structures of the interior emission. We use the results from the models to address the conditions during the supernova explosion, concentrating on asymmetries in the shock structure. We also predict that the back surface of Cassiopeia A will begin brightening in ~30 years, and the front surface in ~100 years.

astro-ph.GA↗

arXiv2008

Spitzer Spectral Mapping of Supernova Remnant Cassiopeia A

We present the global distribution of fine structure infrared line emission in the Cassiopeia A supernova remnant using data from the Spitzer Space Telescope's Infrared Spectrograph. We identify emission from ejecta materials in the interior, prior to their encounter with the reverse shock, as well as from the post-shock bright ring. The global electron density increases by >~100 at the shock to ~10^4 cm^-3, providing evidence for strong radiative cooling. There is also a dramatic change in ionization state at the shock, with the fading of emission from low ionization interior species like [SiII], giving way to [SIV] and, at even further distances, high-energy X-rays from hydrogenic silicon. Two compact, crescent-shaped clumps with highly enhanced neon abundance are arranged symmetrically around the central neutron star. These neon crescents are very closely aligned with the "kick" direction of the compact object from the remnant's expansion center, tracing a new axis of explosion asymmetry. They indicate that much of the apparent macroscopic elemental mixing may arise from different compositional layers of ejecta now passing through the reverse shock along different directions.

astro-ph↗