arXiv subjects

Joseph Gelfand

Publications and source records attributed to Joseph Gelfand.

At least 19 recordsLinked to original sources

arXiv2026

The Twentieth Data Release of the Sloan Digital Sky Survey: First All-Sky BOSS Spectra, eROSITA-SDSS-V Mapper Coordinated Observations, and a Preview of the Local Volume Mapper

This paper presents the twentieth data release (DR20) from the Sloan Digital Sky Survey, the third data release of its fifth generation (SDSS-V). SDSS-V is a panoptic spectroscopy survey that is mapping the stars, gas, and galaxies through three scientific programs: the Milky Way Mapper (MWM), the Local Volume Mapper (LVM), and the Black Hole Mapper (BHM). DR20 presents the first optical (BOSS) SDSS-V spectra from southern hemisphere for the MWM and BHM surveys; new optical MWM and BHM data from the northern hemisphere are also available, for a total over 3 million spectra of 1.5 million stars and half a million galaxies and quasars, with galactic and extragalactic x-ray targets coordinate with eROSITA DR2. DR20 includes integral field spectroscopy maps from LVM of six targets and 169 tiles, spanning Galactic HII regions, planetary nebulae, and nearby galaxies. Additionally, eighteen value added catalogs are also released with DR20, based on SDSS-V MWM and BHM data, and we present a new LVM visualization tool including an RGB HiPS map as a value added product.

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arXiv2026

Chandra X-ray Observations of the Pulsar Wind Nebula within CTA 1

We present deep Chandra observations of the pulsar wind nebula (PWN) powered by PSR J0007+7303 in the composite supernova remnant CTA 1. The merged ACIS image shows a $\sim20''$ jet extending south of the pulsar and bending toward the southwest, a faint counter-jet to the north, and a compact torus oriented approximately perpendicular to the jet axis. Using an archival observation from 2003 we perform relative astrometry over a $\sim20$ yr baseline and constrain the pulsar's transverse velocity to $\lesssim 200~\mathrm{km~s^{-1}}$ at the distance of 1.4 kpc at 95% confidence. Spatially resolved spectroscopy shows hard spectra for the jet and torus (photon indicies $\Gamma \approx 1.2-1.4$) and a softer spectrum for the extended nebula ($\Gamma = 1.85 \pm 0.11$), indicating minimal radiative cooling in the compact regions. Modeling of the torus, associated with the termination shock, as an inclined circle yields a viewing angle $\zeta \approx 50^\circ$. The outer gap and two-pole caustic pulsar emission models then imply a moderate magnetic inclination ($\alpha \sim 20^\circ$-$70^\circ$). Broadband spectral energy distribution (SED) modeling from radio to PeV $\gamma$-rays for a one-zone leptonic scenario yields a low magnetic field ($B \approx 1.4$-$3.2~\mu\mathrm{G}$) and a high electron cutoff energy ($E_{\rm cut} \sim 0.2$-$0.3~\mathrm{PeV}$), indicating that the magnetic field decreases rapidly outside of the compact nebula. These results establish CTA 1 as a young, low X-ray efficiency PWN with a hard injection spectrum capable of accelerating particles to PeV energies.

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arXiv2025

Detection of Diffuse Radio Emission inside the Supernova Remnant G338.3-0.0 associated with the Gamma-ray Source HESS J1640-465

We report the discovery of diffuse radio emission within SNR G338.3-0.0 using new MeerKAT observations at 816 MHz and 1.4 GHz. The radio emission spatially overlaps with the X-ray pulsar wind nebula (PWN) powered by PSR J1640-4631 and the GeV/TeV gamma-ray source HESS J1640-465. The morphology of this radio emission is centrally peaked and its extent is well-contained within the SNR shell. A lack of mid- and far-infrared counterparts and the absence of catalogued H II regions argues against a thermal origin, while the morphology and radial profile are suggestive of a PWN origin powered by PSR J1640-4631. Under this assumption, we use a one-zone, time dependant model to reproduce the size and broadband (radio, X-ray, and gamma-rays) spectral energy distribution of the PWN. The modelling and broadband properties of this PWN suggests it is currently interacting with the reverse shock within its host SNR. This evolutionary stage is associated with particles escaping the PWN and entering the ISM, suggesting this object may be an important source of Galactic PeV e+/e-

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arXiv2025

Sloan Digital Sky Survey-V: Pioneering Panoptic Spectroscopy

The Sloan Digital Sky Survey-V (SDSS-V) is pioneering panoptic spectroscopy: it is the first all-sky, multi-epoch, optical-to-infrared spectroscopic survey. SDSS-V is mapping the sky with multi-object spectroscopy (MOS) at telescopes in both hemispheres (the 2.5-m Sloan Foundation Telescope at Apache Point Observatory and the 100-inch du Pont Telescope at Las Campanas Observatory), where 500 zonal robotic fiber positioners feed light from a wide-field focal plane to an optical (R$\sim 2000$, 500 fibers) and a near-infrared (R$\sim 22,000$, 300 fibers) spectrograph. In addition to these MOS capabilities, the survey is pioneering ultra wide-field ($\sim$ 4000~deg$^2$) integral field spectroscopy enabled by a new dedicated facility (LVM-I) at Las Campanas Observatory, where an integral field spectrograph (IFS) with 1801 lenslet-coupled fibers arranged in a 0.5 degree diameter hexagon feeds multiple R$\sim$4000 optical spectrographs that cover 3600-9800 angstroms. SDSS-V's hardware and multi-year survey strategy are designed to decode the chemo-dynamical history of the Milky Way Galaxy and tackle fundamental open issues in stellar physics in its Milky Way Mapper program, trace the growth physics of supermassive black holes in its Black Hole Mapper program, and understand the self-regulation mechanisms and the chemical enrichment of galactic ecosystems at the energy-injection scale in its Local Volume Mapper program. The survey is well-timed to multiply the scientific output from major all-sky space missions. The SDSS-V MOS programs began robotic operations in 2021; IFS observations began in 2023 with the completion of the LVM-I facility. SDSS-V builds upon decades of heritage of SDSS's pioneering advances in data analysis, collaboration spirit, infrastructure, and product deliverables in astronomy.

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arXiv2025

The Nineteenth Data Release of the Sloan Digital Sky Survey

Mapping the local and distant Universe is key to our understanding of it. For decades, the Sloan Digital Sky Survey (SDSS) has made a concerted effort to map millions of celestial objects to constrain the physical processes that govern our Universe. The most recent and fifth generation of SDSS (SDSS-V) is organized into three scientific ``mappers". Milky Way Mapper (MWM) that aims to chart the various components of the Milky Way and constrain its formation and assembly, Black Hole Mapper (BHM), which focuses on understanding supermassive black holes in distant galaxies across the Universe, and Local Volume Mapper (LVM), which uses integral field spectroscopy to map the ionized interstellar medium in the local group. This paper describes and outlines the scope and content for the nineteenth data release (DR19) of SDSS and the most substantial to date in SDSS-V. DR19 is the first to contain data from all three mappers. Additionally, we also describe nine value added catalogs (VACs) that enhance the science that can be conducted with the SDSS-V data. Finally, we discuss how to access SDSS DR19 and provide illustrative examples and tutorials.

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arXiv2025

Peering into the heart of darkness with VLBA : Radio Quiet AGN in the JWST North Ecliptic Pole Time-Domain Field

We present initial results from the 4.8 GHz Very Long Baseline Array (VLBA) survey of the JWST North Ecliptic Pole Time-Domain Field (TDF). From 106 radio sources found in the Karl G. Jansky Very Large Array observations in the TDF, we detected 12 sources (11% detection rate) at 3.3 $\mu$Jy rms sensitivity and 4 mas resolution. Most detections exhibit pc-scale emission (less than 40 pc) with high VLBA/VLA flux density ratios and brightness temperatures exceeding 10$^5$ K, confirming non-thermal AGN activity. Spectral indices ($>$ -0.5) correlate with higher VLBA/VLA flux ratios, consistent with synchrotron emission from AGN coronae or jets. In the majority of our sources star formation contributes less than 50% of the total VLBA radio emission, with a few cases where the emission is almost entirely AGN-driven. Although the radio emission from radio quiet AGN is thought to be primarily driven by star formation, our VLBA observations confirm that there is also often a contribution at various levels from black hole driven AGN. Eight VLBA detections have JWST/NIRCam counterparts, predominantly early-type, bulge-dominated galaxies, which we use to get an estimate of the redshift and star formation rate (SFR). WISE colors indicate that VLBA detections are either AGN or intermediate-disk-dominated systems, while VLBA non-detections correspond to extended, star-forming galaxies. We compare SFRs derived from previous SCUBA-2 850 $\mu$m observations with new JWST-based estimates, and discuss the observed discrepancies, highlighting JWST's improved capability to disentangle AGN activity from star formation.

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arXiv2024

Parkes Radio and NuSTAR X-ray Observations of the Composite Supernova Remnant B0453-685 in the Large Magellanic Cloud

Gamma-ray emission is observed coincident in position to the evolved, composite supernova remnant (SNR) B0453-685. Prior multi-wavelength investigations of the region indicate that the pulsar wind nebula (PWN) within the SNR is the most likely origin for the observed gamma-rays, with a possible pulsar contribution that becomes significant at energies below E ~ 5GeV. Constraints on the PWN hard X-ray spectrum are important for the most accurate broadband representation of PWN emission and determining the presence of a gamma-ray pulsar component. The results of Parkes radio and NuSTAR X-ray observations are presented on PWN B0453-685. We perform a search for the central pulsar in the new Parkes radio data, finding an upper limit of 12uJy. A pulsation search in the new NuSTAR observation additionally provides a 3sigma upper-limit on the hard X-ray pulsed fraction of 56%. The PWN is best characterized with a photon index Gamma_X = 1.91 +\- 0.20 in the 3-78keV NuSTAR data and the results are incorporated into existing broadband models. Lastly, we characterize a serendipitous source detected by Chandra and NuSTAR that is considered a new high mass X-ray binary candidate.

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arXiv2023

The High Energy X-ray Probe (HEX-P): Galactic PeVatrons, star clusters, superbubbles, microquasar jets, and gamma-ray binaries

HEX-P is a probe-class mission concept that will combine high spatial resolution X-ray imaging (<10" FWHM) and broad spectral coverage (0.2-80 keV) with an effective area far superior to current facilities (including XMM-Newton and NuSTAR) to enable revolutionary new insights into a variety of important astrophysical problems. With the recent discoveries of over 40 ultra-high-energy gamma-ray sources (detected above 100 TeV) and neutrino emission in the Galactic Plane, we have entered a new era of multi-messenger astrophysics facing the exciting reality of Galactic PeVatrons. In the next decade, as more Galactic PeVatrons and TeV gamma-ray sources are expected to be discovered, the identification of their acceleration and emission mechanisms will be the most pressing issue in both particle and high-energy astrophysics. In this paper, along with its companion papers (Reynolds et al. 2023, Mori et al. 2023), we will present that HEX-P is uniquely suited to address important problems in various cosmic-ray accelerators, including Galactic PeVatrons, through investigating synchrotron X-ray emission of TeV-PeV electrons produced by both leptonic and hadronic processes.

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arXiv2023

The High Energy X-ray Probe (HEX-P): Supernova remnants, pulsar wind nebulae, and nuclear astrophysics

HEX-P is a probe-class mission concept that will combine high spatial resolution X-ray imaging ($<10"$ full width at half maximum) and broad spectral coverage (0.2--80 keV) with an effective area far superior to current facilities (including XMM-Newton and NuSTAR) to enable revolutionary new insights into a variety of important astrophysical problems. HEX-P is ideally suited to address important problems in the physics and astrophysics of supernova remnants (SNRs) and pulsar-wind nebulae (PWNe). For shell SNRs, HEX-P can greatly improve our understanding via more accurate spectral characterization and localization of non-thermal X-ray emission from both non-thermal-dominated SNRs and those containing both thermal and non-thermal components, and can discover previously unknown non-thermal components in SNRs. Multi-epoch HEX-P observations of several young SNRs (e.g., Cas A and Tycho) are expected to detect year-scale variabilities of X-ray filaments and knots, thus enabling us to determine fundamental parameters related to diffusive shock acceleration, such as local magnetic field strengths and maximum electron energies. For PWNe, HEX-P will provide spatially-resolved, broadband X-ray spectral data separately from their pulsar emission, allowing us to study how particle acceleration, cooling, and propagation operate in different evolution stages of PWNe. HEX-P is also poised to make unique and significant contributions to nuclear astrophysics of Galactic radioactive sources by improving detections of, or limits on, $^{44}$Ti in the youngest SNRs and by potentially discovering rare nuclear lines as evidence of double neutron star mergers. Throughout the paper, we present simulations of each class of objects, demonstrating the power of both the imaging and spectral capabilities of HEX-P to advance our knowledge of SNRs, PWNe, and nuclear astrophysics.

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arXiv2023

Probing the History of the Galaxy Assembly of the Counter-rotating Disk Galaxy PGC 66551

Stellar counter-rotation in disk galaxies directly relates to the complex phenomenon of the disk mass assembly believed to be driven by external processes, such as accretion and mergers. The detailed study of such systems makes it possible to reveal the source of external accretion and establish the details of this process. In this paper, we investigate the galaxy PGC 66551 (MaNGA ID 1-179561) which hosts two large-scale counter-rotating (CR) stellar disks identified in the Sloan Digital Sky Survey MaNGA data and then confirmed using deep follow-up spectroscopy with the 10m Southern African Large Telescope. We measured the properties of ionized gas and stellar populations of both CR disks in PGC 66551. We found that the CR disk is compact, contains young stars with subsolar metallicity, and has a stellar mass of $5\times10^{9}$ M$_\odot$ which amounts to $\approx$20% of the galaxy's total. Surprisingly, the main 8 Gyr old disk has a significantly lower metallicity of -0.8 dex than other CR galaxies. We developed a simple analytic model of the history of the metal enrichment, which we applied to PGC 66551 and constrained the parameters of the galactic outflow wind, and estimated the metallicity of the infalling gas that formed the CR disk to be -0.9 ... -0.5 dex. Our interpretation prefers a merger with a gas-rich satellite over cold accretion from a cosmic filament as a source of gas, which then formed the CR disk in PGC 66551.

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arXiv2023

Fermi-LAT Gamma-ray Emission Discovered from the Composite Supernova Remnant B0453-685 in the Large Magellanic Cloud

We report the second extragalactic pulsar wind nebula (PWN) to be detected in the MeV-GeV band by the Fermi-LAT, located within the Large Magellanic Cloud (LMC). The only other known PWN to emit in the Fermi band outside of the Milky Way Galaxy is N 157B which lies to the west of the newly detected gamma-ray emission at an angular distance of 4 degrees. Faint, point-like gamma-ray emission is discovered at the location of the composite supernova remnant (SNR) B0453-685 with a ~ 4 sigma significance from energies 300 MeV - 2 TeV. We present the Fermi-LAT data analysis of the new gamma-ray source, coupled with a detailed multi-wavelength investigation to understand the nature of the observed emission. Combining the observed characteristics of the SNR and the physical implications from broadband modeling, we argue it is unlikely the SNR is responsible for the gamma-ray emission. While the gamma-ray emission is too faint for a pulsation search, we try to distinguish between any pulsar and PWN component of SNR B0453-685 that would be responsible for the observed gamma-ray emission using semi-analytic models. We determine the most likely scenario is that the old PWN (t ~ 14,000 years) within B0453-685 has been impacted by the return of the SNR reverse shock with a possible substantial pulsar component below 5 GeV.

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arXiv2022

MeV-GeV Gamma-ray Emission from SNR G327.1-1.1 Discovered by the Fermi-LAT

We report the discovery of MeV-GeV gamma-ray emission by the Fermi-LAT positionally coincident with the TeV pulsar wind nebula (PWN) HESS~J1554-550 within the host supernova remnant (SNR) G327.1-1.1. The gamma-ray emission is point-like and faint but significant (> 4 sigma) in the 300MeV-2TeV energy range. We report here the Fermi-LAT analysis of the observed gamma-ray emission followed by a detailed multiwavelength investigation to understand the nature of the emission. The central pulsar powering the PWN within G327.1-1.1 has not been detected in any waveband; however, it is likely embedded within the X-ray nebula, which is displaced from the center of the radio nebula. The gamma-ray emission is faint and therefore a pulsation search to determine if the pulsar may be contributing is not feasible. Prior detailed multiwavelength reports revealed an SNR system that is old, tau ~ 18,000yrs, where the interaction of the reverse shock with the PWN is underway or has recently occurred. We find that the gamma-ray emission agrees remarkably well with a detailed broadband model constructed in a prior report based on independent hydrodynamical and semi-analytic simulations of an evolved PWN. We further investigate the physical implications of the model for the PWN evolutionary stage incorporating the new Fermi-LAT data and attempt to model the distinct particle components based on a spatial separation analysis of the displaced PWN counterparts.

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arXiv2021

Radio Morphology of Red Geysers

We present 150 MHz, 1.4 GHz, and 3 GHz radio imaging (LoTSS, FIRST and VLASS) and spatially resolved ionized gas characteristics (SDSS IV-MaNGA) for 140 local ($z<0.1$) early-type "red geyser" galaxies. These galaxies have low star formation activity (SFR $\sim \rm 0.01\ M_{\odot} yr^{-1}$), but show unique extended patterns in spatially-resolved emission line maps that have been interpreted as large-scale ionized winds driven by active galactic nuclei (AGN). In this work we confirm that red geysers host low-luminosity radio sources ($\rm L_{1.4GHz} \sim 10^{22} W Hz^{-1}$). Out of 42 radio-detected red geysers, 32 are spatially resolved in LoTSS and FIRST, with radio sizes varying between $\sim 5-25$ kpc. Three sources have radio sizes exceeding 40 kpc. A majority display a compact radio morphology and are consistent with either low-power compact radio sources ("FR0" galaxies) or "radio-quiet quasars". They may be powered by small-scale AGN-driven jets which remain unresolved at the current $5"$ resolution of radio data. The extended radio sources, not belonging to the "compact" morphological class, exhibit steeper spectra with a median spectral index of $-0.67$ indicating the dominance of lobed components. The red geysers hosting extended radio sources also have the lowest specific star formation rates, suggesting they either have a greater impact on the surrounding interstellar medium or are found in more massive halos on average. The degree of alignment of the ionized wind cone and the extended radio features are either 0$^{\circ}$ or 90$^{\circ}$, indicating possible interaction between the interstellar medium and the central radio AGN.

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arXiv2021

NuSTAR broad-band X-ray observational campaign of energetic pulsar wind nebulae in synergy with VERITAS, HAWC and Fermi gamma-ray telescopes

We report recent progress on the on-going NuSTAR observational campaign of 8 TeV-detected pulsar wind nebulae (PWNe). This campaign constitutes a major part of our NuSTAR study of some of the most energetic TeV sources in our Galaxy detected by VERITAS and HAWC. NuSTAR is the first focusing X-ray telescope operating above 10 keV in space with sub-arcminute angular resolution. Broad-band X-ray imaging and spectroscopy data, obtained by NuSTAR, allow us to probe sub-PeV electron populations through detecting synchrotron X-ray radiation. Our targets include PeVatron candidates detected by HAWC, the Boomerang nebula, PWNe crushed by supernova remnant shocks (or relic PWNe) and G0.9+0.1 in the Galactic Center. Using Fermi-LAT data and available TeV data, we aim to provide a complete, multi-wavelength view of a diverse class of middle-aged (~10-100 kyrs old) PWNe. Our NuSTAR analysis detected hard X-ray emission from the Eel and Boomerang PWNe and characterized their broad-band X-ray spectra most accurately. We plan to apply both time-evolution and multi-zone PWN models to multi-wavelength spectral energy distribution (SED) data over the radio, X-ray, GeV and TeV bands. In this proceeding, we will review our observational campaign and discuss the preliminary results for some PWNe.

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arXiv2021

The Green Bank Northern Celestial Cap Pulsar Survey. VI. Timing and Discovery of PSR J1759+5036: A Double Neutron Star Binary Pulsar

The Green Bank North Celestial Cap (GBNCC) survey is a 350-MHz all-sky survey for pulsars and fast radio transients using the Robert C. Byrd Green Bank Telescope. To date, the survey has discovered over 190 pulsars, including 33 millisecond pulsars (MSPs) and 24 rotating radio transients(RRATs). Several exotic pulsars have been discovered in the survey, including PSR J1759+5036, a binary pulsar with a 176-ms spin period in an orbit with a period of 2.04 days, an eccentricity of 0.3,and a projected semi-major axis of 6.8 light seconds. Using seven years of timing data, we are able to measure one post-Keplerian parameter, advance of periastron, which has allowed us to constrain the total system mass to 2.62(3) solar masses. This constraint, along with the spin period and orbital parameters, suggests that this is a double neutron star system, although we cannot entirely rule out a pulsar-white dwarf binary. This pulsar is only detectable in roughly 45% of observations, most likely due to scintillation. However, additional observations are required to determine whether there may be other contributing effects.

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arXiv2020

SDSS-IV MaNGA: The Nature of an Off-galaxy H$α$ Blob -- A Multi-wavelength View of Offset Cooling in a Merging Galaxy Group

Galaxies in dense environments, such as groups and clusters, experience various processes by which galaxies gain and lose gas. Using data from the SDSS-IV MaNGA survey, we previously reported the discovery of a giant (6 -- 8 kpc in diameter) H$α$ blob, Totoro, about 8 kpc away from a pair of galaxies (Satsuki and Mei) residing in a galaxy group which is experiencing a group-group merger. Here, we combine interferometric $^{12}$CO(1--0) molecular gas data, new wide-field H$α$, $u$-band data, and published X-ray data to determine the origin of the blob. Several scenarios are discussed to account for its multi-wavelength properties, including (1) H$α$ gas being stripped from galaxy Satsuki by ram-pressure; (2) a separated low-surface-brightness galaxy; (3) gas being ejected or ionized by an active galactic nucleus (AGN); and (4) a cooling intra-group medium (IGM). Scenarios (1) and (2) are less favored by the present data. Scenario (3) is also less likely as there is no evidence for an active ongoing AGN in the host galaxy. We find that the CO (cold) and H$α$ (warm) gas coexist with X-ray (hot) structures; moreover, the derived cooling time is within the regime where molecular and H$α$ gas are expected. The coexistence of gas with different temperatures also agrees with that of cooling gas in other systems. Our multi-wavelength results strongly suggest that the CO and H$α$ gas are the product of cooling from the IGM at its current location, i.e., cooling has occurred, and may be ongoing, well outside the host-galaxy core.

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arXiv2019

All-sky Medium Energy Gamma-ray Observatory: Exploring the Extreme Multimessenger Universe

The All-sky Medium Energy Gamma-ray Observatory (AMEGO) is a probe class mission concept that will provide essential contributions to multimessenger astrophysics in the late 2020s and beyond. AMEGO combines high sensitivity in the 200 keV to 10 GeV energy range with a wide field of view, good spectral resolution, and polarization sensitivity. Therefore, AMEGO is key in the study of multimessenger astrophysical objects that have unique signatures in the gamma-ray regime, such as neutron star mergers, supernovae, and flaring active galactic nuclei. The order-of-magnitude improvement compared to previous MeV missions also enables discoveries of a wide range of phenomena whose energy output peaks in the relatively unexplored medium-energy gamma-ray band.

astro-ph.IM↗

arXiv2018

Detecting Radio-AGN signatures in Red geysers

A new class of quiescent galaxies harboring possible AGN-driven winds has been discovered using spatially resolved optical spectroscopy from the ongoing SDSS-IV MaNGA survey. These galaxies, termed "red geysers", constitute $5-10\%$ of the local quiescent population and are characterized by narrow bisymmetric patterns in ionized gas emission features. Cheung et al. argued that these galaxies host large-scale AGN-driven winds that may play a role in suppressing star formation at late times. In this work, we test the hypothesis that AGN activity is ultimately responsible for the red geyser phenomenon. We compare the nuclear radio activity of the red geysers to a matched control sample with similar stellar mass, redshift, rest frame $NUV-r$ color, axis ratio and presence of ionized gas. We have used the 1.4 GHz radio continuum data from VLA FIRST survey to stack the radio flux from the red geyser and control samples. In addition to a 3 times higher FIRST detection rate, we find that red geysers have a 5$σ$ higher level of average radio flux than control galaxies. After restricting to rest-frame $NUV-r$ color $>$ 5 and checking mid-IR WISE photometry, we rule out star formation contamination and conclude that red geysers are associated with more active AGN. Red geysers and a possibly-related class with disturbed H$α$ emission account for 40\% of all radio-detected red galaxies with $\rm log~(M_\star/M_\odot) < 11$. Our results support a picture in which episodic AGN activity drives large-scale-relatively weak ionized winds that may provide a feedback mechanism for many early-type galaxies.

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