arXiv subjects

Patrick Hartigan

Publications and source records attributed to Patrick Hartigan.

At least 19 recordsLinked to original sources

arXiv2025

PROJECT-J: the shocking H2 outflow from HH46

We analyze the H2 emission observed in the HH46 Class I system as part of PROJECT-J (Protostellar Jets Cradle Tested with JWST), to investigate the origin and excitation of the warm molecular outflow. We used NIRSpec and MIRI spectral maps (1.6-27.9 microns) to trace the structure and physical conditions of the outflow. By fitting the H2 rotational diagrams with a multi-temperature gas model, we derived key physical parameters including temperature, extinction, column densities, and the ortho-to-para ratio. This information is combined with a detailed kinematical analysis and comparison with irradiated shock models. We find no evidence of H2 temperature or velocity stratification from the axis to the edge of the outflow, as would be expected in MHD disk-wind models and as observed in other outflows. Instead, the observations suggest that the H2 emission arises from shock interactions between jet bow shocks and/or wide-angle winds with the ambient medium and cavity walls. NIRSpec emission and velocity maps reveal expanding molecular shells, likely driven by the less luminous source in the binary system. We infer an accretion rate of less than 10^-9 solar masses per year for the secondary source, approximately one order of magnitude lower than that of the primary. The H2 emission is consistent with excitation by low-velocity (approximately 10 km/s) J-type shocks, irradiated by an external UV field that may originate from strong dissociative shocks driven by the atomic jet. Future JWST observations will further constrain the evolution of the expanding shell and the mechanisms driving the outflow.

astro-ph.GA↗

arXiv2025

A Search for Eclipse Cycles Similar to the Hypersaros: Columbus and the Lunar Eclipse of March 14, 2025

The total lunar eclipse on March 14, 2025 UT occurs nearly exactly 521 years (one Hypersaros) after a similar eclipse on March 1, 1504 UT that is renowned for its importance to the voyage of Columbus to Jamaica. Eclipses separated by a Hypersaros have similar depths, appear very close to the same location in the sky, and occur at nearly the same time of year. This paper summarizes the results from a search for analogous cycles within the Five Millennium Catalogs of Lunar and Solar Eclipses. Under the two simple constraints of similar eclipse dates relative to the vernal equinox and similar paths of the Moon through the Earth's shadow, the most common time intervals between lunar eclipses separated by less than 1000 years are the 521-year Hypersaros and a 633-yr period of the Icosa-Inex-Triple-Saros (IITS). Notable cycles at longer periods occur at 1154, 1284, 1787, 1917, and 2308 years.

astro-ph.EP↗

arXiv2024

PDRs4All VIII: Mid-IR emission line inventory of the Orion Bar

Mid-infrared emission features probe the properties of ionized gas, and hot or warm molecular gas. The Orion Bar is a frequently studied photodissociation region (PDR) containing large amounts of gas under these conditions, and was observed with the MIRI IFU aboard JWST as part of the "PDRs4All" program. The resulting IR spectroscopic images of high angular resolution (0.2") reveal a rich observational inventory of mid-IR emission lines, and spatially resolve the substructure of the PDR, with a mosaic cutting perpendicularly across the ionization front and three dissociation fronts. We extracted five spectra that represent the ionized, atomic, and molecular gas layers, and measured the most prominent gas emission lines. An initial analysis summarizes the physical conditions of the gas and the potential of these data. We identified around 100 lines, report an additional 18 lines that remain unidentified, and measured the line intensities and central wavelengths. The H I recombination lines originating from the ionized gas layer bordering the PDR, have intensity ratios that are well matched by emissivity coefficients from H recombination theory, but deviate up to 10% due contamination by He I lines. We report the observed emission lines of various ionization stages of Ne, P, S, Cl, Ar, Fe, and Ni, and show how certain line ratios vary between the five regions. We observe the pure-rotational H$_2$ lines in the vibrational ground state from 0-0 S(1) to 0-0 S(8), and in the first vibrationally excited state from 1-1 S(5) to 1-1 S(9). We derive H$_2$ excitation diagrams, and approximate the excitation with one thermal (~700 K) component representative of an average gas temperature, and one non-thermal component (~2700 K) probing the effect of UV pumping. We compare these results to an existing model for the Orion Bar PDR and highlight the differences with the observations.

astro-ph.GA↗

arXiv2024

A far-ultraviolet-driven photoevaporation flow observed in a protoplanetary disk

Most low-mass stars form in stellar clusters that also contain massive stars, which are sources of far-ultraviolet (FUV) radiation. Theoretical models predict that this FUV radiation produces photo-dissociation regions (PDRs) on the surfaces of protoplanetary disks around low-mass stars, impacting planet formation within the disks. We report JWST and Atacama Large Millimetere Array observations of a FUV-irradiated protoplanetary disk in the Orion Nebula. Emission lines are detected from the PDR; modelling their kinematics and excitation allows us to constrain the physical conditions within the gas. We quantify the mass-loss rate induced by the FUV irradiation, finding it is sufficient to remove gas from the disk in less than a million years. This is rapid enough to affect giant planet formation in the disk.

astro-ph.GA↗

arXiv2024

High-quality Extragalactic Legacy-field Monitoring (HELM) with DECam

High-quality Extragalactic Legacy-field Monitoring (HELM) is a long-term observing program that photometrically monitors several well-studied extragalactic legacy fields with the Dark Energy Camera (DECam) imager on the CTIO 4m Blanco telescope. Since Feb 2019, HELM has been monitoring regions within COSMOS, XMM-LSS, CDF-S, S-CVZ, ELAIS-S1, and SDSS Stripe 82 with few-day cadences in the $(u)gri(z)$ bands, over a collective sky area of $\sim 38$ deg${\rm ^2}$. The main science goal of HELM is to provide high-quality optical light curves for a large sample of active galactic nuclei (AGNs), and to build decades-long time baselines when combining past and future optical light curves in these legacy fields. These optical images and light curves will facilitate the measurements of AGN reverberation mapping lags, as well as studies of AGN variability and its dependences on accretion properties. In addition, the time-resolved and coadded DECam photometry will enable a broad range of science applications from galaxy evolution to time-domain science. We describe the design and implementation of the program and present the first data release that includes source catalogs and the first $\sim 3.5$ years of light curves during 2019A--2022A.

astro-ph.GA↗

arXiv2023

PDRs4All III: JWST's NIR spectroscopic view of the Orion Bar

(Abridged) We investigate the impact of radiative feedback from massive stars on their natal cloud and focus on the transition from the HII region to the atomic PDR (crossing the ionisation front (IF)), and the subsequent transition to the molecular PDR (crossing the dissociation front (DF)). We use high-resolution near-IR integral field spectroscopic data from NIRSpec on JWST to observe the Orion Bar PDR as part of the PDRs4All JWST Early Release Science Program. The NIRSpec data reveal a forest of lines including, but not limited to, HeI, HI, and CI recombination lines, ionic lines, OI and NI fluorescence lines, Aromatic Infrared Bands (AIBs including aromatic CH, aliphatic CH, and their CD counterparts), CO2 ice, pure rotational and ro-vibrational lines from H2, and ro-vibrational lines HD, CO, and CH+, most of them detected for the first time towards a PDR. Their spatial distribution resolves the H and He ionisation structure in the Huygens region, gives insight into the geometry of the Bar, and confirms the large-scale stratification of PDRs. We observe numerous smaller scale structures whose typical size decreases with distance from Ori C and IR lines from CI, if solely arising from radiative recombination and cascade, reveal very high gas temperatures consistent with the hot irradiated surface of small-scale dense clumps deep inside the PDR. The H2 lines reveal multiple, prominent filaments which exhibit different characteristics. This leaves the impression of a "terraced" transition from the predominantly atomic surface region to the CO-rich molecular zone deeper in. This study showcases the discovery space created by JWST to further our understanding of the impact radiation from young stars has on their natal molecular cloud and proto-planetary disk, which touches on star- and planet formation as well as galaxy evolution.

astro-ph.GA↗

arXiv2023

PDRs4All IV. An embarrassment of riches: Aromatic infrared bands in the Orion Bar

(Abridged) Mid-infrared observations of photodissociation regions (PDRs) are dominated by strong emission features called aromatic infrared bands (AIBs). The most prominent AIBs are found at 3.3, 6.2, 7.7, 8.6, and 11.2 $\mu$m. The most sensitive, highest-resolution infrared spectral imaging data ever taken of the prototypical PDR, the Orion Bar, have been captured by JWST. We provide an inventory of the AIBs found in the Orion Bar, along with mid-IR template spectra from five distinct regions in the Bar: the molecular PDR, the atomic PDR, and the HII region. We use JWST NIRSpec IFU and MIRI MRS observations of the Orion Bar from the JWST Early Release Science Program, PDRs4All (ID: 1288). We extract five template spectra to represent the morphology and environment of the Orion Bar PDR. The superb sensitivity and the spectral and spatial resolution of these JWST observations reveal many details of the AIB emission and enable an improved characterization of their detailed profile shapes and sub-components. While the spectra are dominated by the well-known AIBs at 3.3, 6.2, 7.7, 8.6, 11.2, and 12.7 $\mu$m, a wealth of weaker features and sub-components are present. We report trends in the widths and relative strengths of AIBs across the five template spectra. These trends yield valuable insight into the photochemical evolution of PAHs, such as the evolution responsible for the shift of 11.2 $\mu$m AIB emission from class B$_{11.2}$ in the molecular PDR to class A$_{11.2}$ in the PDR surface layers. This photochemical evolution is driven by the increased importance of FUV processing in the PDR surface layers, resulting in a "weeding out" of the weakest links of the PAH family in these layers. For now, these JWST observations are consistent with a model in which the underlying PAH family is composed of a few species: the so-called 'grandPAHs'.

astro-ph.GA↗

arXiv2023

PDRs4All II: JWST's NIR and MIR imaging view of the Orion Nebula

The JWST has captured the most detailed and sharpest infrared images ever taken of the inner region of the Orion Nebula, the nearest massive star formation region, and a prototypical highly irradiated dense photo-dissociation region (PDR). We investigate the fundamental interaction of far-ultraviolet photons with molecular clouds. The transitions across the ionization front (IF), dissociation front (DF), and the molecular cloud are studied at high-angular resolution. These transitions are relevant to understanding the effects of radiative feedback from massive stars and the dominant physical and chemical processes that lead to the IR emission that JWST will detect in many Galactic and extragalactic environments. Due to the proximity of the Orion Nebula and the unprecedented angular resolution of JWST, these data reveal that the molecular cloud borders are hyper structured at small angular scales of 0.1-1" (0.0002-0.002 pc or 40-400 au at 414 pc). A diverse set of features are observed such as ridges, waves, globules and photoevaporated protoplanetary disks. At the PDR atomic to molecular transition, several bright features are detected that are associated with the highly irradiated surroundings of the dense molecular condensations and embedded young star. Toward the Orion Bar PDR, a highly sculpted interface is detected with sharp edges and density increases near the IF and DF. This was predicted by previous modeling studies, but the fronts were unresolved in most tracers. A complex, structured, and folded DF surface was traced by the H2 lines. This dataset was used to revisit the commonly adopted 2D PDR structure of the Orion Bar. JWST provides us with a complete view of the PDR, all the way from the PDR edge to the substructured dense region, and this allowed us to determine, in detail, where the emission of the atomic and molecular lines, aromatic bands, and dust originate.

astro-ph.GA↗

arXiv2022

Length-scales and Dynamics of Carina's Western Wall

We present a variety of analyses of the turbulent dynamics of the boundary of a photo-dissociation region (PDR) in the Carina Nebula using high resolution ALMA observations. Using Principal Component Analysis we suggest that the turbulence in this molecular cloud is driven at large scales. Analysis of the centroid velocity structure functions indicate that the turbulence is dominated by shocks rather than local (in k-space) transport of energy. We further find that length-scales in the range 0.02 - 0.03 pc are important in the dynamics of this cloud and this finding is supported by analysis of the dominant emission structure length-scale. These length-scales are well resolved by the observational data and we conclude that the apparent importance of this range of scales is physical in origin. Given that it is also well within the range strongly influenced by ambipolar diffusion, we conclude that it is not primarily a product of turbulence alone, but is more likely to be a result of the interplay between gravity and turbulence. Finally, through comparison of these results with previous observations of H2 emission from the Western Wall we demonstrate that observations of a PDR can be used to probe the internal structure of the undisturbed portion of a molecular cloud.

astro-ph.GA↗

arXiv2022

ALMA Datacubes and Continuum Maps of the Irradiated Western Wall in Carina

We present ALMA observations of the continuum and line emission of $^{12}$CO, $^{13}$CO, C$^{18}$O, and [C I] for a portion of the G287.38-0.62 (Car 1-E) region in the Carina star-forming complex. The new data record how a molecular cloud responds on subarcsecond scales when subjected to a powerful radiation front, and provide insights into the overall process of star formation within regions that contain the most massive young stars. The maps show several molecular clouds superpose upon the line of sight, including a portion of the Western Wall, a highly-irradiated cloud situated near the young star cluster Trumpler 14. In agreement with theory, there is a clear progression from fluoresced H$_2$, to [C I], to C$^{18}$O with distance into the PDR front. Emission from optically thick $^{12}$CO extends across the region, while $^{13}$CO, [C I] and especially C$^{18}$O are more optically thin, and concentrate into clumps and filaments closer to the PDR interface. Within the Western Wall cloud itself we identify 254 distinct core-sized clumps in our datacube of C$^{18}$O. The mass distribution of these objects is similar to that of the stellar IMF. Aside from a large-scale velocity gradient, the clump radial velocities lack any spatial coherence size. There is no direct evidence for triggering of star formation in the Western Wall in that its C$^{18}$O clumps and continuum cores appear starless, with no pillars present. However, the densest portion of the cloud lies closest to the PDR, and the C$^{18}$O emission is flattened along the radiation front.

astro-ph.GA↗

arXiv2022

Rubin Observatory LSST Transients and Variable Stars Roadmap

The Vera C. Rubin Legacy Survey of Space and Time holds the potential to revolutionize time domain astrophysics, reaching completely unexplored areas of the Universe and mapping variability time scales from minutes to a decade. To prepare to maximize the potential of the Rubin LSST data for the exploration of the transient and variable Universe, one of the four pillars of Rubin LSST science, the Transient and Variable Stars Science Collaboration, one of the eight Rubin LSST Science Collaborations, has identified research areas of interest and requirements, and paths to enable them. While our roadmap is ever-evolving, this document represents a snapshot of our plans and preparatory work in the final years and months leading up to the survey's first light.

astro-ph.IM↗

arXiv2022

SpinSpotter: An Automated Algorithm for Identifying Stellar Rotation Periods With Autocorrelation Analysis

Spinspotter is a robust and automated algorithm designed to extract stellar rotation periods from large photometric datasets with minimal supervision. Our approach uses the autocorrelation function (ACF) to identify stellar rotation periods up to one-third the observational baseline of the data. Our algorithm also provides a suite of diagnostics that describe the features in the ACF, which allows the user to fine-tune the tolerance with which to accept a period detection. We apply it to approximately 130,000 main-sequence stars observed by the Transiting Exoplanet Survey Satellite (TESS) at 2-minute cadence during Sectors 1-26, and identify rotation periods for 13,504 stars ranging from 0.4 to 14 days. We demonstrate good agreement between our sample and known values from the literature and note key differences between our population of rotators and those previously identified in the Kepler field, most notably a large population of fast-rotating M dwarfs. Our sample of rotating stars provides a data set with coverage of nearly the entire sky that can be used as a basis for future gyrochronological studies, and, when combined with proper motions and distances from Gaia, to search for regions with high densities of young stars, thus identifying areas of recent star formation and undiscovered moving group members. Our algorithm is publicly available for download and use on GitHub.

astro-ph.SR↗

arXiv2022

PDRs4All: A JWST Early Release Science Program on radiative feedback from massive stars

Massive stars disrupt their natal molecular cloud material through radiative and mechanical feedback processes. These processes have profound effects on the evolution of interstellar matter in our Galaxy and throughout the Universe, from the era of vigorous star formation at redshifts of 1-3 to the present day. The dominant feedback processes can be probed by observations of the Photo-Dissociation Regions (PDRs) where the far-ultraviolet photons of massive stars create warm regions of gas and dust in the neutral atomic and molecular gas. PDR emission provides a unique tool to study in detail the physical and chemical processes that are relevant for most of the mass in inter- and circumstellar media including diffuse clouds, proto-planetary disks and molecular cloud surfaces, globules, planetary nebulae, and star-forming regions. PDR emission dominates the infrared (IR) spectra of star-forming galaxies. Most of the Galactic and extragalactic observations obtained with the James Webb Space Telescope (JWST) will therefore arise in PDR emission. In this paper we present an Early Release Science program using the MIRI, NIRSpec, and NIRCam instruments dedicated to the observations of an emblematic and nearby PDR: the Orion Bar. These early JWST observations will provide template datasets designed to identify key PDR characteristics in JWST observations. These data will serve to benchmark PDR models and extend them into the JWST era. We also present the Science-Enabling products that we will provide to the community. These template datasets and Science-Enabling products will guide the preparation of future proposals on star-forming regions in our Galaxy and beyond and will facilitate data analysis and interpretation of forthcoming JWST observations.

astro-ph.GA↗

arXiv2022

Experimental observations of detached bow shock formation in the interaction of a laser-produced plasma with a magnetized obstacle

The magnetic field produced by planets with active dynamos, like the Earth, can exert sufficient pressure to oppose supersonic stellar wind plasmas, leading to the formation of a standing bow shock upstream of the magnetopause, or pressure-balance surface. Scaled laboratory experiments studying the interaction of an inflowing solar wind analog with a strong, external magnetic field are a promising new way to study magnetospheric physics and to complement existing models, although reaching regimes favorable for magnetized shock formation is experimentally challenging. This paper presents experimental evidence of the formation of a magnetized bow shock in the interaction of a supersonic, super-Alfvénic plasma with a strongly magnetized obstacle at the OMEGA laser facility. The solar wind analog is generated by the collision and subsequent expansion of two counter-propagating, laser-driven plasma plumes. The magnetized obstacle is a thin wire, driven with strong electrical currents. Hydrodynamic simulations using the FLASH code predict the colliding plasma source meets the criteria for bow shock formation. Spatially resolved, optical Thomson scattering measures the electron number density, and optical emission lines provide a measurement of the plasma temperature, from which we infer the presence of a fast magnetosonic shock far upstream of the obstacle. Proton images provide a measure of large-scale features in the magnetic field topology, and reconstructed path-integrated magnetic field maps from these images suggest the formation of a bow shock upstream of the wire and as a transient magnetopause. We compare features in the reconstructed fields to two-dimensional MHD simulations of the system.

physics.plasm-ph↗

arXiv2021

Probing jets from young embedded sources: clues from HST near-IR [Fe II] images

We present near-infrared [Fe II] images of four Class 0/I jets (HH 1/2, HH 34, HH 111, HH 46/47) observed with the Hubble Space Telescope Wide Field Camera 3. The unprecedented angular resolution allows us to measure proper motions, jet widths and trajectories, and extinction along the jets. In all cases, we detect the counter-jet which was barely visible or invisible at shorter wavelengths. We measure tangential velocities of a few hundred km/s, consistent with previous HST measurements over 10 years ago. We measure the jet width as close as a few tens of au from the star, revealing high collimations of about 2 degrees for HH 1, HH 34, HH 111 and about 8 degrees for HH 46, all of which are preserved up to large distances. For HH 34, we find evidence of a larger initial opening angle of about 7 degrees. Measurement of knot positions reveals deviations in trajectory of both the jet and counter-jet of all sources. Analysis of asymmetries in the inner knot positions for HH 111 suggests the presence of a low mass stellar companion at separation 20-30 au. Finally, we find extinction values of 15-20 mag near the source which gradually decreases moving downstream along the jet. These observations have allowed us to study the counter-jet at unprecedented high angular resolution, and will be a valuable reference for planning future JWST mid-infrared observations which will peer even closer into the jet engine.

astro-ph.SR↗

arXiv2020

A JWST Preview: Adaptive-Optics Images of H$_2$, Br-$γ$, and K-continuum in Carina's Western Wall

We present the first wide-field near-infrared adaptive optics images of Carina's Western Wall (G287.38-0.62), one of the brightest and most well-defined irradiated interfaces known in a region of massive star formation. The new narrowband H$_2$ 2.12$μ$m, Br-$γ$ and K-continuum images trace the photoevaporative flow from the cloud and identify locations where UV-radiation from the surrounding massive stars excites molecular hydrogen to fluoresce. With a field of view of $\sim$ 1.5' $\times$ 2.9' and spatial resolution between 60 $-$ 110 mas, the new images show a spectacular level of detail over a large area, and presage what JWST should achieve. The Wall is convex in shape, with a large triangular-shaped extension near its apex. The interface near the apex consists of 3 $-$ 4 regularly-spaced ridges with projected spacings of $\sim$ 2000 AU, suggestive of a large-scale dynamically-important magnetic field. The northern edge of the Wall breaks into several swept-back fragments of width $\sim$ 1800 AU that resemble Kelvin-Helmholtz instabilities, and the southern part of the Wall also shows complex morphologies including a sinusoidal-like variation with a half-wavelength of 2500 AU. Though the dissociation front must increase the density along the surface of the Wall, it does not resolve into pillars that point back to the ionization sources, as could occur if the front triggered new stars to form. We discovered that MHO 1630, an H$_2$ outflow with no clear driving source in the northern portion of the Wall, consists of a series of bow shocks arrayed in a line.

astro-ph.GA↗

arXiv2020

Emission-Line Datacubes of the HH 32 Stellar Jet

We analyze datacubes of over 60 emission lines in the HH 32 stellar jet acquired with the Keck Cosmic Web Imager (KCWI). The data cover the less-explored blue portion of the spectrum between 3586A and 6351A , and have both high spectral (R $\sim$ 10000) and spatial ($\lesssim$ 1" ) resolution. The study includes all three major ionization states of oxygen, three Balmer lines, multiple lines of Fe II and Fe III, as well as the first datacubes ever acquired for important unblended diagnostic lines such as He II $λ$4686, Ca I $λ$3933, and Mg I] $λ$4571. The data cubes generally sort according to excitation, and have a relatively continuous progression from the highest-excitation ions (He II, O III) through the intermediate-excitation ions (O I and H I) to the lowest-excitation ions (Ca II and Mg I). Merging the KCWI cubes with HST images leads to several new insights about the flow, including evidence for bow shocks, partial bow shocks, spur shocks, Mach disks, jet deflection shocks, a wiggling jet, and potential shock precursors. The most surprising result is that one of the velocity components of Fe II in the Mach disk suddenly increases in flux relative to other lines by a factor of two, implying that the Mach disk vaporizes dust in the jet. Hence, jets must accelerate or entrain dust to speeds of over 300 km/s without destroying the grains.

astro-ph.GA↗

arXiv2018

Young Stars and their Variability with LSST

Young stars exhibit short-term photometric variability caused by mass accretion events from circumstellar disks, the presence of dusty warps within the inner disks, starspots that rotate across the stellar surfaces, and flares. Long-term variability also occurs owing to starspot longevity and cycles, and from changes in stellar angular momenta and activity as the stars age. We propose to observe the Carina star-forming region in different bands with a cadence of 30 minutes every night for one week per year to clarify the nature of both the short-term and long-term variability of the thousands of young stars in this region. By obtaining well-sampled multicolor lightcurves of this dense young cluster, LSST would acquire the first statistically significant data on how these objects vary on both short and long timescales. This information will allow us to relate the observed variability to stellar properties such as mass, age, binarity, and to environmental properties such as location within or exterior to the H II region, and to the presence or absence of a circumstellar disk.

astro-ph.SR↗