More Like this

1. The Panchromatic Hubble Andromeda Treasury: Triangulum Extended Region (PHATTER). III. The Mass Function of Young Stellar Clusters in M33

   https://doi.org/10.3847/1538-4357/ac51cf  

   Wainer, Tobin M. ; Johnson, L. Clifton ; Seth, Anil C. ; TorresVillanueva, Estephani E. ; Dalcanton, Julianne J. ; Durbin, Meredith J. ; Dolphin, Andrew ; Weisz, Daniel R. ; Williams, Benjamin F. ; PHATTER Collaboration ( March 2022 , The Astrophysical Journal)

   We measure the star cluster mass function (CMF) for the Local Group galaxy M33. We use the catalog of stellar clusters selected from the Panchromatic Hubble Andromeda Treasury: Triangulum Extended Region survey. We analyze 711 clusters in M33 with$7.0<\log (\mathrm{Age}/\mathrm{yr})<8.5$, and log(M/M_⊙) > 3.0 as determined from color–magnitude diagram fits to individual stars. The M33 CMF is best described by a Schechter function with power-law slopeα= −${2.06}_{-0.13}^{+0.14}$, and truncation mass log(M_c/M_⊙)$={4.24}_{-0.13}^{+0.16}$. The data show strong evidence for a high-mass truncation, thus strongly favoring a Schechter function fit over a pure power law. M33's truncation mass is consistent with the previously identified linear trend betweenM_c, and star formation rate surface density, Σ_SFR. We also explore the effect that individual cluster mass uncertainties have on derived mass function parameters, and find evidence to suggest that large cluster mass uncertainties have the potential to bias the truncation mass of fitted mass functions at the 1σlevel.

    

   more » « less
2. The PHANGS-HST Survey: Physics at High Angular Resolution in Nearby Galaxies with the Hubble Space Telescope

   https://doi.org/10.3847/1538-4365/ac1fe5  

   Lee, Janice C. ; Whitmore, Bradley C. ; Thilker, David A. ; Deger, Sinan ; Larson, Kirsten L. ; Ubeda, Leonardo ; Anand, Gagandeep S. ; Boquien, Médéric ; Chandar, Rupali ; Dale, Daniel A. ; et al ( January 2022 , The Astrophysical Journal Supplement Series)

   Abstract The PHANGS program is building the first data set to enable the multiphase, multiscale study of star formation across the nearby spiral galaxy population. This effort is enabled by large survey programs with the Atacama Large Millimeter/submillimeter Array (ALMA), MUSE on the Very Large Telescope, and the Hubble Space Telescope (HST), with which we have obtained CO(2–1) imaging, optical spectroscopic mapping, and high-resolution UV–optical imaging, respectively. Here, we present PHANGS-HST, which has obtained NUV– U – B – V – I imaging of the disks of 38 spiral galaxies at distances of 4–23 Mpc, and parallel V - and I -band imaging of their halos, to provide a census of tens of thousands of compact star clusters and multiscale stellar associations. The combination of HST, ALMA, and VLT/MUSE observations will yield an unprecedented joint catalog of the observed and physical properties of ∼100,000 star clusters, associations, H ii regions, and molecular clouds. With these basic units of star formation, PHANGS will systematically chart the evolutionary cycling between gas and stars across a diversity of galactic environments found in nearby galaxies. We discuss the design of the PHANGS-HST survey and provide an overview of the HST data processing pipeline and first results. We highlight new methods for selecting star cluster candidates, morphological classification of candidates with convolutional neural networks, and identification of stellar associations over a range of physical scales with a watershed algorithm. We describe the cross-observatory imaging, catalogs, and software products to be released. The PHANGS high-level science products will seed a broad range of investigations, in particular, the study of embedded stellar populations and dust with the James Webb Space Telescope, for which a PHANGS Cycle 1 Treasury program to obtain eight-band 2–21 μ m imaging has been approved. 

   more » « less
3. Clusters, clouds, and correlations: relating young clusters to giant molecular clouds in M33 and M31

   https://doi.org/10.1093/mnras/stad1430  

   Peltonen, Joshua ; Rosolowsky, Erik ; Johnson, L. Clifton ; Seth, Anil C. ; Dalcanton, Julianne ; Bell, Eric F. ; Braine, Jonathan ; Koch, Eric W. ; Lazzarini, Margaret ; Leroy, Adam K. ; et al ( May 2023 , Monthly Notices of the Royal Astronomical Society)

   We use young clusters and giant molecular clouds (GMCs) in the galaxies M33 and M31 to constrain temporal and spatial scales in the star formation process. In M33, we compare the Panchromatic Hubble Andromeda Treasury: Triangulum Extended Region (PHATTER) catalogue of 1214 clusters with ages measured via colour–magnitude diagram (CMD) fitting to 444 GMCs identified from a new 35 pc resolution Atacama Large Millimeter/submillimeter Array (ALMA) 12CO(2–1) survey. In M31, we compare the Panchromatic Hubble Andromeda Treasury (PHAT) catalogue of 1249 clusters to 251 GMCs measured from a Combined Array for Research in Millimeter-wave Astronomy (CARMA) 12CO(1–0) survey with 20 pc resolution. Through two-point correlation analysis, we find that young clusters have a high probability of being near other young clusters, but correlation between GMCs is suppressed by the cloud identification algorithm. By comparing the positions, we find that younger clusters are closer to GMCs than older clusters. Through cross-correlation analysis of the M33 cluster data, we find that clusters are statistically associated when they are ≤10 Myr old. Utilizing the high precision ages of the clusters, we find that clusters older than ≈18 Myr are uncorrelated with the molecular interstellar medium (ISM). Using the spatial coincidence of the youngest clusters and GMCs in M33, we estimate that clusters spend ≈4–6 Myr inside their parent GMC. Through similar analysis, we find that the GMCs in M33 have a total lifetime of ≈11–15 Myr. We also develop a drift model and show that the above correlations can be explained if the clusters in M33 have a 5–10 km s−1 velocity dispersion relative to the molecular ISM.

    

   more » « less
4. Looking for Obscured Young Star Clusters in NGC 1313

   https://doi.org/10.3847/1538-4357/abe0b5  

   Messa, Matteo ; Calzetti, Daniela ; Adamo, Angela ; Grasha, Kathryn ; Johnson, Kelsey E. ; Sabbi, Elena ; Smith, Linda J. ; Bajaj, Varun ; Finn, Molly K. ; Lin, Zesen ( March 2021 , The Astrophysical Journal)

   Abstract Using recently acquired Hubble Space Telescope NIR observations ( J , Pa β , and H bands) of the nearby galaxy NGC 1313, we investigate the timescales required by a young star cluster to emerge from its natal cloud. We search for extincted star clusters, potentially embedded in their natal cloud as either (1) compact sources in regions with high H α /Pa β extinctions or (2) compact H ii regions that appear as point-like sources in the Pa β emission map. The NUV–optical–NIR photometry of the candidate clusters is used to derive their ages, masses, and extinctions via a least- χ 2 spectral energy distribution broad- and narrowband fitting process. The 100 clusters in the final samples have masses in the range and moderate extinctions, E ( B − V ) ≲ 1.0 mag. Focusing on the young clusters (0–6 Myr), we derive a weak correlation between extinction and age of the clusters. Almost half of the clusters have low extinctions, E ( B − V ) < 0.25 mag, already at very young ages (≤3 Myr), suggesting that dust is quickly removed from clusters. A stronger correlation is found between the morphology of the nebular emission (compact, partial or absent, both in H α and Pa β ) and cluster age. Relative fractions of clusters associated with a specific nebular morphology are used to estimate the typical timescales for clearing the natal gas cloud, resulting in between 3 and 5 Myr, ∼1 Myr older than what was estimated from NUV–optical-based cluster studies. This difference hints at a bias for optical-only-based studies, which James Webb Space Telescope will address in the coming years. 

   more » « less
5. Nitrogen-enriched, Highly Pressurized Nebular Clouds Surrounding a Super Star Cluster at Cosmic Noon

   https://doi.org/10.3847/1538-4357/acf75c  

   Pascale, Massimo ; Dai, Liang ; McKee, Christopher F. ; Tsang, Benny T. -H. ( November 2023 , The Astrophysical Journal)

   Strong lensing offers a precious opportunity for studying the formation and early evolution of super star clusters that are rare in our cosmic backyard. The Sunburst Arc, a lensed Cosmic Noon galaxy, hosts a young super star cluster with escaping Lyman continuum radiation. Analyzing archival Hubble Space Telescope images and emission line data from Very Large Telescope/MUSE and X-shooter, we construct a physical model for the cluster and its surrounding photoionized nebula. We confirm that the cluster is ≲4 Myr old, is extremely massiveM_⋆∼ 10⁷M_⊙, and yet has a central component as compact as several parsecs, and we find a gas-phase metallicityZ= (0.22 ± 0.03)Z_⊙. The cluster is surrounded by ≳10⁵M_⊙of dense clouds that have been pressurized toP∼ 10⁹K cm⁻³by perhaps stellar radiation at within 10 pc. These should have large neutral columnsN_HI> 10^22.8cm⁻²to survive rapid ejection by radiation pressure. The clouds are likely dusty as they show gas-phase depletion of silicon, and may be conducive to secondary star formation ifN_HI> 10²⁴cm⁻²or if they sink farther toward the cluster center. Detecting strong [Niii]λλ1750,1752, we infer heavy nitrogen enrichment$\log (\mathrm{N}/\mathrm{O})=-{0.21}_{-0.11}^{+0.10}$. This requires efficiently retaining ≳500M_⊙of nitrogen in the high-pressure clouds from massive stars heavier than 60M_⊙up to 4 Myr. We suggest a physical origin of the high-pressure clouds from partial or complete condensation of slow massive star ejecta, which may have an important implication for the puzzle of multiple stellar populations in globular clusters.

    

   more » « less