About

Stacey Alberts is an Assistant Research Professor at Steward Observatory. She earned her Ph.D. in 2014 from the University of Massachusetts, Amherst. Her research focuses on galaxy evolution in the context of local environment through studies of massive galaxy clusters out to high redshift. She utilizes multi-wavelength observations, focusing on the mid-infrared to submillimeter, to characterize star formation and active galactic nuclei (AGN) in cluster and field galaxies up to redshift approximately 2. Her work aims to determine how environment influences galaxy properties and contributes to the quenched nature of cluster galaxies today. At Arizona, she has joined the Mid-Infrared Instrument (MIRI) team and is involved in planning early observations in preparation for the launch of the James Webb Space Telescope.

Research topics

• Astronomy
• Physics
• Computer Science
• Astrophysics
• History
• Astrobiology
• Remote sensing
• Geology
• Art

Selected publications

• JADES: Rest-frame UV-to-NIR Size Evolution of Massive Quiescent Galaxies from Redshift <i>z</i> = 5 to <i>z</i> = 0.5

  The Astrophysical Journal · 2026-02-13 · 10 citations

  preprintOpen access

  Abstract We present the UV-to-near-IR (NIR) size evolution of a sample of 161 quiescent galaxies with M * &gt; 10 10 M ⊙ over 0.5 &lt; z &lt; 5. With deep multiband NIRCam images in GOODS-South from JADES, we measure the effective radii ( R e ) of the galaxies at rest-frame 0.3, 0.5, and 1 μ m. On average, we find that quiescent galaxies are 45% (15%) more compact at rest-frame 1 μ m than they are at 0.3 μ m (0.5 μ m). Regardless of wavelengths, the R e of quiescent galaxies strongly evolves with redshift, and this evolution depends on stellar mass. For lower-mass quiescent galaxies with M * = 10 10 –10 10.6 M ⊙ , the evolution follows R e ∝ (1 + z ) −1.1 , whereas it becomes steeper, following R e ∝ (1 + z ) −1.7 , for higher-mass quiescent galaxies with M * &gt; 10 10.6 M ⊙ . To constrain the physical mechanisms driving the apparent size evolution, we study the relationship between R e and the formation redshift ( z form ) of quiescent galaxies. For lower-mass quiescent galaxies, this relationship is broadly consistent with <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>R</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>e</mml:mi> </mml:mrow> </mml:msub> <mml:mo>∝</mml:mo> <mml:msup> <mml:mrow> <mml:mo stretchy="false">(</mml:mo> <mml:mn>1</mml:mn> <mml:mo>+</mml:mo> <mml:msub> <mml:mrow> <mml:mi>z</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">form</mml:mi> </mml:mrow> </mml:msub> <mml:mo stretchy="false">)</mml:mo> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msup> </mml:math> , in line with the expectation of the progenitor effect. For higher-mass quiescent galaxies, the relationship between R e and z form depends on stellar age. Older quiescent galaxies have a steeper relationship between R e and z form than that expected from the progenitor effect alone, suggesting that mergers and/or post-quenching continuous gas accretion drive additional size growth in very massive systems. We find that the z &gt; 3 quiescent galaxies in our sample are very compact, with mass surface densities Σ e ≳ 10 10 M ⊙ kpc −2 , and their R e are possibly even smaller than anticipated from the size evolution measured for lower-redshift quiescent galaxies. Finally, we take a close look at the structure of GS-9209, one of the earliest confirmed massive quiescent galaxies at z spec ∼ 4.7. From UV to NIR, GS-9209 becomes increasingly compact, and its light profile becomes more spheroidal, showing that the color gradient is already present in this earliest massive quiescent galaxy.

  PublisherDOI

• Filling the Gap in Cluster Evolution: JWST's Glimpse into a Young, Star-Forming Cluster at Cosmic Noon

  Open MIND · 2026-02-27

  preprint

  We present a detailed study of HUDFJ0332.4-2746.6 (HUDF46), a $z \approx 1.84$ overdensity in the Hubble Ultra Deep Field, previously identified with HST as a proto-cluster. JWST/NIRISS spectroscopy expands its confirmed membership from 18 to 37 galaxies, while deep HST/ACS, JWST/NIRCam, and JWST/MIRI imaging provide a comprehensive multiwavelength view from the rest-frame UV to the mid-infrared. This dataset probes the population across three dex in stellar mass ($M_\bigstar \approx 10^{7.5\text{--}10.5}\,M_\odot$), delivering the first direct view of a young cluster down to such low-$M_\bigstar$ at $z\gtrsim1$. Assuming virialization, we derive a velocity dispersion of $σ\approx 670\pm 91\,\mathrm{km\,s^{-1}}$ and a halo mass of $M_{200} \approx (1.2\pm0.2) \times 10^{14}\,M_\odot$, in agreement with X-ray constraints from deep {\it Chandra} data. Despite residing in a massive halo likely in the hot-halo regime, the population is overwhelmingly star-forming, with no established red sequence and no extended X-ray emission from a hot intracluster medium. HUDF46 members have stellar and structural properties nearly indistinguishable from coeval field galaxies, and the structure hosts only one AGN candidate, found in its brightest galaxy, which lies at the cluster center. Overall, HUDF46 appears to be in a transitional phase prior to the onset of environmental quenching, making its galaxy population a key benchmark for tracing the processes that will later build a passive population and shape the assembly of massive clusters at later cosmic times.

  DOI

• JWST Advanced Deep Extragalactic Survey (JADES) Data Release 5: NIRCam Imaging in GOODS-S and GOODS-N

  ArXiv.org · 2026-01-22

  articleOpen access

  We present the Near Infrared Camera (NIRCam) imaging products of the fifth data release (DR5) of the James Webb Space Telescope (JWST) Advanced Deep Extragalactic Survey (JADES). The JADES survey is one of the most ambitious programs yet conducted on JWST, producing deep infrared imaging and multiobject spectroscopy on the GOODS-S and GOODS-N extragalactic deep fields in order to explore galaxies to the earliest epoch. Here we describe the NIRCam data reduction procedures that result in deep and well-characterized mosaics in up to 18 filters covering 469 arcmin$^2$, with 250 arcmin$^2$ having at least 8 filters of coverage. This release contains the full NIRCam imaging of JADES, over 800 JWST mission hours, as well as co-reductions of 19 other programs in these two premier deep fields. We perform detailed tests on the final data products, thereby characterizing the photometric properties, point-spread function, and astrometric alignment. We release mosaics for individual programs (or epochs, depending on scheduling) and the mosaics combining data from all programs in order to facilitate photometric variability studies and the deepest possible photometry.

  PublisherOA PDF

• JWST Advanced Deep Extragalactic Survey (JADES) Data Release 5: Photometric Catalog

  arXiv (Cornell University) · 2026-01-22 · 2 citations

  preprintOpen access

  JADES Data Release 5 (DR5) photometric catalogs and describes the methodologies used for source detection, deblending, photometry, uncertainty estimation, and catalog curation. The catalogs are constructed from 35 space-based imaging mosaics obtained with JWST/NIRCam, JWST/MIRI, HST/ACS, and HST/WFC3, combining approximately 1250 hours of JADES imaging with extensive additional public JWST and HST observations in the GOODS fields. Sources are identified using custom signal-to-noise-based detection and deblending algorithms optimized for the depth, resolution, and complex point-spread-function structure of JWST imaging. Source centroids, shapes, and photometric apertures are determined using a new fast two-dimensional Gaussian regression method applied to detection-image profiles. We provide forced circular-aperture photometry, ellipsoidal Kron photometry, and curve-of-growth measurements for every source in every band. We introduce a new pixel-level regression framework to model photometric uncertainties as a function of aperture size and local mosaic properties, accounting for correlated noise in heterogeneous JWST mosaics. Photometric redshifts are computed using template-based fitting applied to both small-aperture photometry on unconvolved images and Kron photometry on common-PSF mosaics. The JADES DR5 catalogs supersede previous JADES photometric releases, and are publicly released through the Mikulski Archive for Space Telescopes and an interactive web interface.

  PublisherDOI

• Calibrating Photometric Mid-Infrared Star Formation Rates for JWST

  arXiv (Cornell University) · 2026-04-01

  articleOpen access1st authorCorresponding

  The mid-infrared (IR) spectrum of galaxies has a long history as a valuable proxy for the dust-obscured star formation rate (SFR) in massive galaxies. Now, with JWST, we can explore the mid-IR's full potential as a SFR tracer over four orders of magnitude in total infrared luminosity (9<~log LIR/Lo<~13). First, combining the SMILES and FRESCO surveys, we evaluate MIRI photometry against the Pa-alpha emission line - a gold standard SFR indicator - in Main Sequence (MS) galaxies at cosmic noon. We find the rest-frame 6-8um luminosity has a steeply superlinear relation with SFR(Pa-alpha) below ~8 Mo/yr, in contrast with the unity slope seen in coeval massive galaxies. We derive broken power-law SFR indicators from single-band MIRI photometry plus a representative dust template, with a scatter typical of IR SFRs (~0.2-0.3 dex). Despite the break in the mid-IR behavior and our simplifying assumption of a single dust SED, we next successfully formulate a UV+IR composite relation (scatter ~0.15 dex) under the usual assumption of energy balance. This implies that the rest-frame 6-8um primarily tracks the global dust-obscuration fraction - which decreases rapidly at log M*/Mo<~10 - rather than reflecting a deficit in PAH abundances at low mass. Our results thus support MIRI photometry as a robust SFR proxy at log M*/Mo>~9 up to z~3. Finally, extending to local and z>~1 ultraluminous infrared galaxies not represented in SMILES, we examine when Pa-alpha and the IR reliably track SFR in the bright regime.

  PublisherOA PDF

• SMILES Data Release. II. Probing Galaxy Evolution during Cosmic Noon and Beyond with NIRSpec Medium-resolution Spectra

  The Astrophysical Journal · 2026-01-29 · 2 citations

  articleOpen access

  Abstract We present the second data release of the Systematic Mid-Infrared Instrument Legacy Extragalactic Survey (SMILES), focusing on JWST/NIRSpec medium-resolution spectroscopy of galaxies across cosmic time. This release includes spectroscopic observations of 166 galaxies spanning 0 &lt; z &lt; 7.5, sampling star-forming galaxies, quiescent systems, and active galactic nuclei (AGNs), with an emphasis on galaxies at cosmic noon ( z ∼ 1–3). We describe the target selection strategy, the observational setup with the G140M/F100LP and G235M/F170LP gratings, and the data calibration process. The final data products include the reduced spectra, redshift catalog, emission-line catalogs produced with GELATO for emission-line galaxies and pPXF fits for quiescent systems, and ancillary spectral energy distribution fit results derived from multiband photometry. The SMILES NIRSpec dataset enables investigations of obscured AGNs, multiphase outflows, ionizing properties, and the role of environment in galaxy evolution. All data products are publicly available through STScI/MAST at https://archive.stsci.edu/hlsp/smiles .

  PublisherDOI

• Halfway to the Peak: Kinematic Signatures of Stable Rotating Disks in Luminous Infrared Galaxies at z=0.5-0.6

  arXiv (Cornell University) · 2026-04-27

  preprintOpen access

  We present a kinematic study of six infrared-luminous galaxies observed with the Mid-InfraRed Instrument Medium-Resolution Spectrometer (MIRI/MRS) onboard JWST. These galaxies lie at $z = 0.5$--$0.6$, midway between the present day and the peak of cosmic star formation. Our sample spans a range of star formation (SF) and active galactic nucleus (AGN) contributions to the mid-infrared emission. We characterize the dynamical state of these IR-luminous galaxies and assess how AGN activity influences the kinematics of the interstellar medium. Using mid-IR atomic lines, we map galaxy kinematics beyond the local Universe for the first time. The spatial resolution of MIRI/MRS (3.0 kpc for 0.46$\arcsec$ at z $\sim$ 0.55) allows us to resolve the internal kinematics of our targets. We compute kinematic maps in three different emission lines ([Ar II]6.99$μ$m, [Ne II]12.81$μ$m, and H$_2$ 0-0 S(5)6.91$μ$m). Using the [Ar II]6.99$μ$m kinematic maps, we derive rotation curves for these sources. All galaxies exhibit ordered rotation, with \(V/σ\geq 2\), consistent with stable disks. Although some show minor disturbances, we find no strong evidence for recent major mergers or galaxy-wide ionized outflows. We find no correlation between \(V/σ\) and AGN fraction, suggesting AGN activity does not significantly disrupt global kinematics or that disk disruption is not required to trigger AGN. However, galaxies with higher AGN fractions show elevated central dispersions, indicating localized turbulence, possibly due to AGN feedback, stellar feedback, accretion or bulge structure. These IR-luminous galaxies likely represent mature, rotationally supported disks, with AGN activation occurring after disk assembly.

  PublisherDOI

• The Way We Tally Becomes the Tale: the Impact of Selection Strategies on the Inferred Evolution of Little Red Dots Across Cosmic Time

  arXiv (Cornell University) · 2026-04-08

  preprintOpen access

  Little Red Dots (LRDs) have emerged as a key population linked to early black hole growth, yet photometric selections have predominantly targeted only the most extreme red systems, thereby shaping our current understanding of this new population of objects. In this work, we deliberately explore a broad range of optical redness while enforcing stringent compactness and visual inspection to ensure robustness and minimize contamination. Leveraging the depth and multiwavelength coverage of the JWST Advanced Deep Extragalactic Survey (JADES) data in the GOODS-North and GOODS-South fields, we construct the largest photometric census of LRDs to date in these fields, comprising 412 sources over $z\approx2\text{--}11$ across $\approx349.6$ arcmin$^2$. We show that classic extreme color cuts isolate only a minor fraction of this population ($\lesssim25\%$), while the majority of LRDs span a broader, largely unexplored parameter space. We quantify how selection strategies impact UV and optical luminosity functions and number density evolution, finding that current demographic trends of LRDs are strongly driven by selection biases and further limited by incomplete identification at both high and low redshift. Spectroscopically confirmed LRDs reveal a continuous range of spectral shapes, consistent with varying Active Galactic Nucleus (AGN) and host contributions in agreement with recent findings. Our results demonstrate that commonly adopted, purity-driven selections bias current demographic constraints toward the most extreme systems, potentially misrepresenting the diversity and evolution of the LRD population. Accounting for these selection effects is essential for interpreting LRDs and their role in early black hole growth.

  PublisherDOI

• The Way We Tally Becomes the Tale: the Impact of Selection Strategies on the Inferred Evolution of Little Red Dots Across Cosmic Time

  ArXiv.org · 2026-04-08

  articleOpen access

  Little Red Dots (LRDs) have emerged as a key population linked to early black hole growth, yet photometric selections have predominantly targeted only the most extreme red systems, thereby shaping our current understanding of this new population of objects. In this work, we deliberately explore a broad range of optical redness while enforcing stringent compactness and visual inspection to ensure robustness and minimize contamination. Leveraging the depth and multiwavelength coverage of the JWST Advanced Deep Extragalactic Survey (JADES) data in the GOODS-North and GOODS-South fields, we construct the largest photometric census of LRDs to date in these fields, comprising 412 sources over $z\approx2\text{--}11$ across $\approx349.6$ arcmin$^2$. We show that classic extreme color cuts isolate only a minor fraction of this population ($\lesssim25\%$), while the majority of LRDs span a broader, largely unexplored parameter space. We quantify how selection strategies impact UV and optical luminosity functions and number density evolution, finding that current demographic trends of LRDs are strongly driven by selection biases and further limited by incomplete identification at both high and low redshift. Spectroscopically confirmed LRDs reveal a continuous range of spectral shapes, consistent with varying Active Galactic Nucleus (AGN) and host contributions in agreement with recent findings. Our results demonstrate that commonly adopted, purity-driven selections bias current demographic constraints toward the most extreme systems, potentially misrepresenting the diversity and evolution of the LRD population. Accounting for these selection effects is essential for interpreting LRDs and their role in early black hole growth.

  PublisherOA PDF

• JWST Advanced Deep Extragalactic Survey (JADES) Data Release 5: MIRI Coordinated Parallels in GOODS-S and GOODS-N

  ArXiv.org · 2026-01-22

  articleOpen access1st authorCorresponding

  Medium to ultra-deep mid-infrared imaging surveys with the James Webb Space Telescope (JWST)'s Mid-Infrared Instrument (MIRI) are reframing our view of the early Universe, from the emergence of ultra-red dusty and quiescent galaxies to the epoch of reionization to the first galaxies. Here we present the MIRI coordinated parallels component of the JADES program, which obtained ultra-deep (155 ks) imaging at $7.7 μ$m over $\sim10$ arcmin$^2$ as well as medium depth ($\sim5-15$ ks) imaging at $7.7, 12.8$, and $15 μ$m over $\sim36$, 25, and 22 arcmin$^2$, respectively, in the GOODS-S and GOODS-N fields. This paper describes the data reduction, which combines the official JWST Calibration Pipeline with custom steps to optimize flagging of warm/hot pixels and optimize background subtraction. We further introduce a new step to address artifacts caused by persistence from saturating sources. The final, fully reduced JADES/MIRI mosaics are being released as part of JADES Data Release 5, along with prior-based forced photometry using NIRCam detection images, providing critical rest-frame near-infrared and optical constraints on early galaxy populations.

  PublisherOA PDF

Frequent coauthors

• S. Charlot

  Sorbonne Université

  104 shared

• Christina C. Williams

  NSF’s NOIRLab

  91 shared

• G. H. Rieke

  University of Arizona

  82 shared

• Sandro Tacchella

  University of Cambridge

  75 shared

• R. Maiolino

  73 shared

• Brant Robertson

  University of California, Santa Cruz

  72 shared

• Zhiyuan Ji

  72 shared

• Chris J. Willott

  70 shared

Education

• PhD, Astronomy Department

  University of Massachusetts Amherst

  2014

• BSc in Astronomy and Physics, Department of Astronomy

  University of Illinois

  2007

Awards & honors

• Kenneth G. Gibbs Doctoral Fellowship in Astronomy and Astrop…