About

Kevin A. Bundy is an Assistant Professor in the Department of Astronomy & Astrophysics at the University of California, Santa Cruz. As an observational astronomer, he specializes in mapping the distribution, properties, and internal structure of galaxies across large cosmic volumes to address key questions about their formation and assembly history. His research combines statistical analyses of large survey programs with targeted observations from premier facilities such as the Keck Observatory. Bundy is particularly interested in the mechanisms that shut down star formation in galaxies and regulate their growth and assembly. He is the founder and Principal Investigator of the MaNGA (Mapping Nearby Galaxies at Apache Point Observatory) survey, one of three programs in the fourth Sloan Digital Sky Survey (SDSS-IV). MaNGA achieved its goal in August 2020 of resolved spectroscopy for an unprecedented 10,000 galaxies, producing over 200 papers by 2020 that provide insights into galaxy life histories, early formation, ongoing growth, and the processes that cause star formation to cease. Bundy also leads the Keck-FOBOS instrument project and an initiative at UCSC to develop the field of astrophotonics, building new tools to enhance future astronomical instruments. His work extends to developing observational and interpretative frameworks to exploit large-volume data sets from high-precision galaxy evolution surveys, addressing questions about galaxy growth, hierarchical assembly, and population transformations.

Research topics

• Computer Science
• Astronomy
• Physics
• Astrophysics
• Internal medicine
• Geometry
• Physical therapy
• Medicine
• Geography
• Gerontology
• Geology
• Psychiatry
• Remote sensing
• Database
• Meteorology

Selected publications

• MSA-3D: Dissecting Galaxies at <i>z</i> ∼ 1 with High Spatial and Spectral Resolution

  The Astrophysical Journal · 2025-04-15 · 3 citations

  articleOpen access

  Abstract Integral field spectroscopy (IFS) is a powerful tool for understanding the formation of galaxies across cosmic history. We present the observing strategy and first results of MSA-3D, a novel JWST program using multi-object spectroscopy in a slit-stepping strategy to produce IFS data cubes. The program observed 43 normal star-forming galaxies at redshifts 0.5 ≲ z ≲ 1.5, corresponding to the epoch when spiral thin-disk galaxies of the modern Hubble sequence are thought to emerge, obtaining kiloparsec-scale maps of rest-frame optical nebular emission lines with spectral resolution R ≃ 2700. Here we describe the multiplexed slit-stepping method, which is &gt;15 times more efficient than the NIRSpec IFS mode for our program. As an example of the data quality, we present a case study of an individual galaxy at z = 1.104 (stellar mass M * = 10 10.3 M ⊙ , star formation rate, SFR = 3 M ⊙ yr −1 ) with prominent face-on spiral structure. We show that the galaxy exhibits a rotationally supported disk with moderate velocity dispersion ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>σ</mml:mi> <mml:mo>=</mml:mo> <mml:mn>3</mml:mn> <mml:msubsup> <mml:mrow> <mml:mn>6</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>4</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>5</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> km s −1 ), a negative radial metallicity gradient (−0.020 ± 0.002 dex kpc −1 ), a dust attenuation gradient, and an exponentially decreasing SFR density profile that closely matches the stellar continuum. These properties are characteristic of local spirals, indicating that mature galaxies are in place at z ∼ 1. We also describe the customized data reduction and original cube-building software pipelines that we have developed to exploit the powerful slit-stepping technique. Our results demonstrate the ability of JWST slit-stepping to study galaxy populations at intermediate to high redshifts, with data quality similar to current surveys of the z ∼ 0.1 Universe.

  PublisherDOI

• Experimental validation of photonic lantern imaging and wavefront sensing performance

  2025-09-18 · 2 citations

  article

  Photonic lanterns (PLs) are fiber-based waveguides that are capable of focal-plane wavefront sensing while simultaneously directing light to downstream science instruments. The optimal choice of wavefront reconstruction algorithm has yet to be determined and likely depends on the particular observing scenario under consideration. Previous work in simulation suggests that PLs can be used for nonlinear wavefront sensing for several applications, including sensing the low-wind effect and correcting large-amplitude aberrations. We present the design of muirSEAL (miniature IR SEAL), a testbed designed to test PL wavefront reconstruction over Zernike modes and segmented-mirror offsets. We demonstrate throughput and linear wavefront reconstruction at multiple f-numbers. We further present initial laboratory imaging of a new photonic lantern fabricated at Lawrence Livermore National Laboratory.

  PublisherDOI

• Integrated, waveguide-based spectrometer for high-performance applications

  2025-03-19

  article
  PublisherDOI

• Morphology and Stellar Populations of a Candidate Ultra-diffuse Galaxy in Early Euclid and Rubin Imaging

  Research Notes of the AAS · 2025-07-15 · 2 citations

  articleOpen accessSenior authorCorresponding

  Abstract We present multi-wavelength imaging and analysis of a low surface brightness (LSB) dwarf galaxy in the Extended Chandra Deep Field South (ECDFS), SMDG0333094–280938, with particular emphasis on data from the Euclid space telescope and from the Vera C. Rubin Observatory. The galaxy is clumpy and blue, and appears to host globular clusters (GCs), suggesting a distance of ∼50–60 Mpc which would make the dwarf an ultra-diffuse galaxy (UDG). We carry out spectral energy distribution fitting from the far-ultraviolet to the near-infrared, in order to estimate the galaxy age and metallicity. We infer a recent peak of star formation that may have led to the formation of the UDG through feedback-driven expansion. This early analysis illustrates how Euclid and Rubin are poised to identify and characterize many thousands of UDGs and other LSB galaxies in the near future, including their GCs and stellar populations.

  PublisherDOI

• MSA-3D: Metallicity Gradients in Galaxies at z ∼ 1 with JWST/NIRSpec Slit-stepping Spectroscopy

  The Astrophysical Journal Letters · 2025-01-09 · 14 citations

  articleOpen accessCorresponding

  Abstract The radial gradient of gas-phase metallicity is a powerful probe of the chemical and structural evolution of star-forming galaxies, closely tied to disk formation and gas kinematics in the early Universe. We present spatially resolved chemical and dynamical properties for a sample of 25 galaxies at 0.5 ≲ z ≲ 1.7 from the MSA-3D survey. These innovative observations provide 3D spectroscopy of galaxies at a spatial resolution approaching JWST’s diffraction limit and a high spectral resolution of R ≃ 2700. The metallicity gradients measured in our galaxy sample range from −0.03 to 0.02 dex kpc −1 . Most galaxies exhibit negative or flat radial gradients, indicating lower metallicity in the outskirts or uniform metallicity throughout the entire galaxy. We confirm a tight relationship between stellar mass and metallicity gradient at z ∼ 1 with small intrinsic scatter of 0.02 dex kpc −1 . Our results indicate that metallicity gradients become increasingly negative as stellar mass increases, likely because the more massive galaxies tend to be more “disky.” This relationship is consistent with the predictions from cosmological hydrodynamic zoom-in simulations with strong stellar feedback. This work presents the effort to harness the multiplexing capability of the JWST NIRSpec microshutter assembly in slit-stepping mode to map the chemical and kinematic profiles of high-redshift galaxies in large samples and at high spatial and spectral resolution.

  PublisherOA PDFDOI

• An Unexplained Origin for the Unusual Globular Cluster System in the Ultradiffuse Galaxy FCC 224

  The Astrophysical Journal · 2025-03-11 · 7 citations

  articleOpen access

  Abstract We study the quiescent ultradiffuse galaxy FCC 224 in the Fornax cluster using Hubble Space Telescope (HST) imaging, motivated by peculiar properties of its globular cluster (GC) system revealed in shallower imaging. The surface brightness fluctuation distance of FCC 224 measured from HST is 18.6 ± 2.7 Mpc, consistent with the Fornax cluster distance. We use Prospector to infer the stellar population from a combination of multiwavelength photometry (HST, ground-based, Wide-field Infrared Survey Explorer) and Keck Cosmic Web Imager spectroscopy. The galaxy has a mass-weighted age of ∼10 Gyr, metallicity [M/H] of ∼−1.25 dex, and a very short formation e -folding time of τ ∼ 0.3 Gyr. Its 12 candidate GCs exhibit highly homogeneous g 475 − I 814 colors, merely 0.04 mag bluer than the diffuse starlight, which supports a single-burst formation scenario for this galaxy. We confirm a top-heavy GC luminosity function, similar to the two dark matter deficient galaxies NGC 1052-DF2 and DF4. However, FCC 224 differs from those galaxies with relatively small GC sizes of ∼3 pc (∼35% smaller than typical for other dwarfs), and with radial mass segregation in its GC system. We are not yet able to identify a formation scenario to explain all of the GC properties in FCC 224. Follow-up measurements of the dark matter content in FCC 224 will be crucial because of the mix of similarities and differences among FCC 224, DF2, and DF4.

  PublisherDOI

• Asymmetric drift in MaNGA: mass and radially dependent stratification rates in galaxy discs

  Monthly Notices of the Royal Astronomical Society · 2024-05-06 · 6 citations

  articleOpen access

  ABSTRACT We measure the age–velocity relationship from the lag between ionized gas and stellar tangential speeds in ∼500 nearby disc galaxies from MaNGA in Sloan Digital Sky Survey IV (SDSS-IV). Selected galaxies are kinematically axisymmetric. Velocity lags are asymmetric drift, seen in the Milky Way’s (MW) solar neighbourhood and other Local Group galaxies; their amplitude correlates with stellar population age. The trend is qualitatively consistent in rate ($\dot{\sigma }$) with a simple power-law model where σ ∝ tb that explains the dynamical phase-space stratification in the solar neighbourhood. The model is generalized based on disc dynamical times to other radii and other galaxies. We find in-plane radial stratification parameters σ0,r (dispersion of the youngest populations) in the range of 10–40 km s−1 and 0.2 &amp;lt; br &amp;lt; 0.5 for MaNGA galaxies. Overall, brincreases with galaxy mass, decreases with radius for galaxies above 10.4 dex (M⊙) in stellar mass, but is ∼constant with radius at lower mass. The measurement scatter indicates the stratification model is too simple to capture the complexity seen in the data, unsurprising given the many possible astrophysical processes that may lead to stellar population dynamical stratification. None the less, the data show dynamical stratification is broadly present in the galaxy population, with systematic trends in mass and density. The amplitude of the asymmetric drift signal is larger for the MaNGA sample than the MW, and better represented in the mean by what is observed in the discs of M31 and M33. Either typical discs have higher surface-density or, more likely, are dynamically hotter (hence thicker) than the MW.

  PublisherOA PDFDOI

• The Sloan Digital Sky Survey Reverberation Mapping Project: Key Results

  The Astrophysical Journal Supplement Series · 2024-05-15 · 82 citations

  articleOpen access

  Abstract We present the final data from the Sloan Digital Sky Survey (SDSS) Reverberation Mapping (RM) project, a precursor to the SDSS-V Black Hole Mapper RM program. This data set includes 11 yr photometric and 7 yr spectroscopic light curves for 849 broad-line quasars over a redshift range of 0.1 &lt; z &lt; 4.5 and a luminosity range of L bol = 10 44−47.5 erg s −1 , along with spectral and variability measurements. We report 23, 81, 125, and 110 RM lags (relative to optical continuum variability) for broad H α , H β , Mg ii , and C iv using the SDSS-RM sample, spanning much of the luminosity and redshift ranges of the sample. Using 30 low-redshift RM active galactic nuclei with dynamical-modeling black hole masses, we derive a new estimate of the average virial factor of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mfenced close="〉" open="〈"> <mml:mrow> <mml:mi>log</mml:mi> <mml:mi>f</mml:mi> </mml:mrow> </mml:mfenced> <mml:mo>=</mml:mo> <mml:mn>0.62</mml:mn> <mml:mo>±</mml:mo> <mml:mn>0.07</mml:mn> </mml:math> for the line dispersion measured from the rms spectrum. The intrinsic scatter of individual virial factors is 0.31 ± 0.07 dex, indicating a factor of 2 systematic uncertainty in RM black hole masses. Our lag measurements reveal significant R – L relations for H β and Mg ii at high redshift, consistent with the latest measurements based on heterogeneous samples. While we are unable to robustly constrain the slope of the R – L relation for C iv given the limited dynamic range in luminosity, we found substantially larger scatter in C iv lags at fixed L 1350 . Using the SDSS-RM lag sample, we derive improved single-epoch (SE) mass recipes for H β , Mg ii , and C iv , which are consistent with their respective RM masses as well as between the SE recipes from two different lines, over the luminosity range probed by our sample. The new H β and Mg ii recipes are approximately unbiased estimators at given RM masses, but there are systematic biases in the C iv recipe. The intrinsic scatter of SE masses around RM masses is ∼0.45 dex for H β and Mg ii , increasing to ∼0.58 dex for C iv .

  PublisherOA PDFDOI

• Design and status update of the AMASE-P project

  2024-06-14

  article

  The Affordable Multiple Aperture Spectroscopy Explorer (AMASE) is a planned high-resolution spatially-resolved spectroscopy survey of the interstellar medium in the Milky Way and nearby galaxies. The prototype telescope and instrument system, AMASE-P, is under development. We provide an update on the instrument design and report the status of this project. A major design change from the previous report is the use of fused silica etched grating in place of VPH grating. The new gratings would provide a significant improvement in the high-efficiency bandwidth of the spectrograph. For fiber positioning on the pseudo-slit, we adopted a new design for the fiber slit blocks to reduce the risk of damaging the fibers during the fiber insertion process and to strengthen the mechanical property of the blocks. We have also chosen octagonal fibers for more uniform near-field and far-field light outputs to yield more stable line spread function. We report the progress of the project and challenges we encountered.

  PublisherDOI

• Photonic lantern testing on Lick Observatory’s 3m Shane Telescope

  2024-06-14 · 1 citations

  article

  Astrophotonics, with its potential for creating low-cost, mass-producible devices, offers a path to dramatically reduce the cost of future astronomical spectrographs. However, coupling the light from large astronomical telescopes into small, photonic chip-based instruments remains a challenge. Photonic lanterns offer a potential solution. Photonic lanterns predictably decompose the inherently multimode light from a ground-based telescope into a series of single-mode outputs, thus eliminating the need for exotic optical elements or extreme AO to achieve high efficiency. We have built a custom assembly for the AO system at Lick Observatory’s 3m Shane Telescope to test photonic lantern behavior on-sky. Here we report on multiple nights of observations over the past year using a lantern with a design wavelength of 1550 nm. Our data reveals the lantern’s basic performance over a 605–1000 nm band and its time domain response to turbulent PSFs with AO correction residuals. These measurements are important for determining the efficacy of future efforts to preferentially select or combine output modes in “real-world” scenarios across scientifically useful bandwidths.

  PublisherDOI

Recent grants

• Red Geyser Galaxies and the Suppression of Star Formation

  NSF · $279k · 2018–2022

• Collaborative Research: A Tunable Astrophotonic Spectrometer with Adaptive Faint-Source Extraction

  NSF · $672k · 2022–2026

Frequent coauthors

• Dmitry Bizyaev

  New Mexico State University

  151 shared

• Éric Emsellem

  135 shared

• Matthew A. Bershady

  111 shared

• Niv Drory

  The University of Texas at Austin

  103 shared

• David A. Wake

  102 shared

• D. Thomas

  University of Portsmouth

  95 shared

• David R. Law

  94 shared

• Karen L. Masters

  93 shared

Labs

• Kevin A Bundy's LabPI

  Galaxy formation and evolution

Education

• Ph.D., Astronomy

  University of California, Santa Cruz

  1998

• M.S., Astronomy

  University of California, Santa Cruz

  1993

• B.A., Astronomy

  University of California, Santa Cruz

  1991

Awards & honors

• Tinsley Visiting Scholar, UT Austin, 2014
• Robert J. Trumpler Award, 2009
• Dorothea Klumpkea Roberts Prize, UC Berkeley, 2000