Stellar structures, molecular gas, and star formation across the PHANGS sample of nearby galaxies
M. Querejeta, E. Schinnerer, S. Meidt, J. Sun, A. K. Leroy, E. Emsellem, R. S. Klessen, J. C. Munoz-Mateos, H. Salo, E. Laurikainen, I. Beslic, G. A. Blanc, M. … 展开作者
M. Querejeta, E. Schinnerer, S. Meidt, J. Sun, A. K. Leroy, E. Emsellem, R. S. Klessen, J. C. Munoz-Mateos, H. Salo, E. Laurikainen, I. Beslic, G. A. Blanc, M. Chevance, D. A. Dale, C. Eibensteiner, C. Faesi, A. Garcia-Rodriguez, S. C. O. Glover, K. Grasha, J. Henshaw, C. Herrera, A. Hughes, K. Kreckel, J. M. D. Kruijssen, D. Liu, E. J. Murphy, H. -A. Pan, J. Pety, A. Razza, E. Rosolowsky, T. Saito, A. Schruba, A. Usero, E. J. Watkins, T. G. Williams
备注：
28 pages, 11 figures, accepted for publication in A&A
We identify stellar structures in the PHANGS sample of 74 nearby galaxies and construct morphological masks of sub-galactic environments based on Spitzer 3.6 micron images. At the simplest level, we distinguish centres, bars, spiral arms, interarm and discs without strong spirals. Slightly more sophisticated masks include rings and lenses, publicly released but not explicitly used in this paper. We examine trends using PHANGS-ALMA CO(2-1) intensity maps and tracers of star formation. The interarm regions and discs without strong spirals dominate in area, whereas molecular gas and star formation are quite evenly distributed among the five basic environments. We reproduce the molecular Kennicutt-Schmidt relation with a slope compatible with unity within the uncertainties, without significant slope differences among environments. In contrast to early studies, we find that bars are not always deserts devoid of gas and star formation, but instead they show large diversity. Similarly, spiral arms do not account for most of the gas and star formation in disc galaxies, and they do not have shorter depletion times than the interarm regions. Spiral arms accumulate gas and star formation, without systematically boosting the star formation efficiency. Centres harbour remarkably high surface densities and on average shorter depletion times than other environments. Centres of barred galaxies show higher surface densities and wider distributions compared to the outer disc; yet, depletion times are similar to unbarred galaxies, suggesting highly intermittent periods of star formation when bars episodically drive gas inflow, without enhancing the central star formation efficiency permanently. In conclusion, we provide quantitative evidence that stellar structures in galaxies strongly affect the organisation of molecular gas and star formation, but their impact on star formation efficiency is more subtle.
The PHANGS-Hα survey. Ground-based narrow-band imaging of nearby star-forming galaxies
Universidad de Chile（智利大学）；Carnegie Institution for Science（卡内基科学机构）；University of Western Australia（西澳大利亚大学）；European Southern Observatory（欧洲南方天文台）；Max-Planck-Institut für Astronomie（马克斯·普朗克天文学研究所）；Tamkang University（淡江大学）；INAF – Osservatorio Astrofisico di Arcetri（意大利国家天体物理研究所阿切特里天文台）；Université Côte d’Azur（蔚蓝海岸大学）；University of Alberta（阿尔伯塔大学）；Universität Heidelberg（海德堡大学）
Tracing the earliest stages of star and cluster formation in 19 nearby galaxies with PHANGS-JWST and HST: compact 3.3 $μ$m PAH emitters and their relation to the optical census of star clusters
The PHANGS program is building the first dataset to enable the multi-phase, multi-scale study of star formation across the nearby spiral galaxy population. This effort is enabled by large survey programs with ALMA, VLT/MUSE, and 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 five band 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 com…
We present a comparison of theoretical predictions of dust continuum and polycyclic aromatic hydrocarbon (PAH) emission with new JWST observations in three nearby galaxies: NGC 628, NGC 1365, and NGC 7496. Our analysis focuses on a total of 1063 compact stellar clusters and 2654 stellar associations previously characterized by HST in the three galaxies. We find that the distributions and trends in the observed PAH-focused infrared colors generally agree with theoretical expectations, and that the bulk of the observations is more aligned with models of larger, ionized PAHs. These JWST data ushe…
We present an innovative and widely applicable approach for the detection and classification of stellar clusters, developed for the PHANGS-HST Treasury Program, an $NUV$-to-$I$ band imaging campaign of 38 spiral galaxies. Our pipeline first generates a unified master source list for stars and candidate clusters, to enable a self-consistent inventory of all star formation products. To distinguish cluster candidates from stars, we introduce the Multiple Concentration Index (MCI) parameter, and measure inner and outer MCIs to probe morphology in more detail than with a single, standard concentrat…
The PHANGS collaboration has been building a reference dataset for the multi-scale, multi-phase study of star formation and the interstellar medium in nearby galaxies. With the successful launch and commissioning of JWST, we can now obtain high-resolution infrared imaging to probe the youngest stellar populations and dust emission on the scales of star clusters and molecular clouds ($\sim$5-50 pc). In Cycle 1, PHANGS is conducting an 8-band imaging survey from 2-21$μ$m of 19 nearby spiral galaxies. CO(2-1) mapping, optical integral field spectroscopy, and UV-optical imaging for all 19 galaxies…
In the hierarchical view of star formation, giant molecular gas clouds (GMCs) undergo fragmentation to form small-scale structures made up of stars and star clusters. Here we study the connection between young star clusters and cold gas across a range of extragalactic environments by combining the high resolution (1") PHANGS-ALMA catalogue of GMCs with the star cluster catalogues from PHANGS-HST. The star clusters are spatially matched with the GMCs across a sample of 11 nearby star-forming galaxies with a range of galactic environments (centres, bars, spiral arms, etc.). We find that after 4-…
The relative distribution of molecular gas and star formation in galaxies gives insight into the physical processes and timescales of the cycle between gas and stars. In this work, we track the relative spatial configuration of CO and H$α$ emission at high resolution in each of our galaxy targets, and use these measurements to quantify the distributions of regions in different evolutionary stages of star formation: from molecular gas without star formation traced by H$α$ to star-forming gas, and to HII regions. The large sample, drawn from the Physics at High Angular resolution in Nearby Galax…
The PHANGS-AstroSat Atlas of Nearby Star Forming Galaxies
University of Alberta（阿尔伯塔大学）；Harvard & Smithsonian（哈佛-史密森天体物理中心）；University of Calgary（卡尔加里大学）；The Johns Hopkins University（约翰斯·霍普金斯大学）；The Ohio State University（俄亥俄州立大学）；Max Planck Institut für Astronomie（马克斯·普朗克天文研究所）；INAF — Osservatorio Astrofisico di Arcetri（意大利国家天体物理研究所阿切特里天文台）；Argelander-Institut für Astronomie, Universität Bonn（波恩大学阿尔兰德天体物理研究所）；Instituto de Alta Investigación, Universidad de Tarapacá（塔拉帕卡大学高级研究院）
We present PHANGS-ALMA, the first survey to map CO J=2-1 line emission at ~1" ~ 100pc spatial resolution from a representative sample of 90 nearby (d<~20 Mpc) galaxies that lie on or near the z=0 "main sequence" of star-forming galaxies. CO line emission traces the bulk distribution of molecular gas, which is the cold, star-forming phase of the interstellar medium. At the resolution achieved by PHANGS-ALMA, each beam reaches the size of a typical individual giant molecular cloud (GMC), so that these data can be used to measure the demographics, life-cycle, and physical state of molecular cloud…
The Milky Way Joins the Extragalactic World: I. PHANGS
The University of Texas at Austin（德克萨斯大学奥斯汀分校）；INAF-IAPS（意大利国家天体物理研究所空间天文与物理学中心）；INAF, Sezione di Lecce（意大利国家天体物理研究所莱切分部）；University of Kentucky（肯塔基大学）；National Astronomical Observatory of Japan（日本国立天文台）；Max Planck Institute for Radio Astronomy（马克斯·普朗克射电天文研究所）；The Ohio State University（俄亥俄州立大学）
(Abridged) We present a cloud decomposition of $^{12}$CO (2--1) observations of the merger and nearest luminous infrared galaxy, NGC 3256. 185 spatially and spectrally resolved clouds are identified across the central $\approx$ 130 kpc$^{2}$ at 90 pc resolution and completeness is estimated. We compare our cloud catalogue from NGC 3256 to ten galaxies observed in the PHANGS-ALMA survey. Distributions in NGC 3256 of cloud velocity dispersions, luminosities, CO-estimated masses, mass surface densities, virial masses, virial parameters, size-linewidth coefficients, and internal turbulent pressure…
JWST observations of polycyclic aromatic hydrocarbon (PAH) emission provide some of the deepest and highest resolution views of the cold interstellar medium (ISM) in nearby galaxies. If PAHs are well mixed with the atomic and molecular gas and illuminated by the average diffuse interstellar radiation field, PAH emission may provide an approximately linear, high resolution, high sensitivity tracer of diffuse gas surface density. We present a pilot study that explores using PAH emission in this way based on MIRI observations of IC 5332, NGC 628, NGC 1365, and NGC 7496 from the PHANGS-JWST Treasu…
We present maps of the 3.3 micron polycyclic aromatic hydrocarbon (PAH) emission feature in NGC 628, NGC 1365, and NGC 7496 as observed with the Near-Infrared Camera (NIRCam) imager on JWST from the PHANGS-JWST Cycle 1 Treasury project. We create maps that isolate the 3.3 micron PAH feature in the F335M filter (F335M$_{\rm PAH}$) using combinations of the F300M and F360M filters for removal of starlight continuum. This continuum removal is complicated by contamination of the F360M by PAH emission and variations in the stellar spectral energy distribution slopes between 3.0 and 3.6 micron. We m…
Mapping star-formation rates (SFR) within galaxies is key to unveiling their assembly and evolution. Calibrations exist for computing SFR from a combination of ultraviolet and infrared bands for galaxies as integrated systems, but their applicability to sub-galactic (kpc) scales remains largely untested. Here we use integral field spectroscopy of 19 nearby ($D <$ 20 Mpc) galaxies obtained by PHANGS-MUSE to derive accurate Balmer decrements (H$α$/H$β$) and attenuation-corrected H$α$ maps. We combine this information with mid-infrared maps from WISE at 22 $\rm μm$, and ultraviolet maps from GALE…
We present improved methods for segmenting CO emission from galaxies into individual molecular clouds, providing an update to the CPROPS algorithms presented by Rosolowsky & Leroy (2006; arXiv:astro-ph/0601706 ). The new code enables both homogenization of the noise and spatial resolution among data, which allows for rigorous comparative analysis. The code also models the completeness of the data via false source injection and includes an updated segmentation approach to better deal with blended emission. These improved algorithms are implemented in a publicly available python package, PYCPROP…
Time-scales of polycyclic aromatic hydrocarbon and dust continuum emission from gas clouds compared to molecular gas cloud lifetimes in PHANGS-JWST galaxies
The earliest stages of star formation, when young stars are still deeply embedded in their natal clouds, represent a critical phase in the matter cycle between gas clouds and young stellar regions. Until now, the high-resolution infrared observations required for characterizing this heavily obscured phase (during which massive stars have formed, but optical emission is not detected) could only be obtained for a handful of the most nearby galaxies. One of the main hurdles has been the limited angular resolution of the Spitzer Space Telescope. With the revolutionary capabilities of the JWST, it …
We provide new planetary nebula luminosity function (PNLF) distances to 19 nearby spiral galaxies that were observed with VLT/MUSE by the PHANGS collaboration. Emission line ratios are used to separate planetary nebulae (PNe) from other bright [OIII] emitting sources like compact supernovae remnants (SNRs) or HII regions. While many studies have used narrowband imaging for this purpose, the detailed spectral line information provided by integral field unit (IFU) spectroscopy grants a more robust way of categorising different [OIII] emitters. We investigate the effects of SNR contamination on t…
Duration and properties of the embedded phase of star formation in 37 nearby galaxies from PHANGS-JWST
Zentrum für Astronomie der Universität Heidelberg（海德堡大学天文中心）；Cosmic Origins Of Life (COOL) Research DAO（生命宇宙起源（COOL）研究DAO）；Kavli Institute for Particle Astrophysics & Cosmology, Stanford University（斯坦福大学卡弗里粒子天体物理与宇宙学研究所）；INAF — Osservatorio Astrofisico di Arcetri（意大利国家天体物理研究所阿切特里天文台）；European Southern Observatory（欧洲南方天文台）；Department of Physics, University of Arkansas（阿肯色大学物理系）；Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Laboratoire Lagrange（蔚蓝海岸大学、蔚蓝海岸天文台、法国国家科学研究中心拉格朗日实验室）；Department of Astronomy, The Ohio State University（俄亥俄州立大学天文学系）
PHANGS-HST is an ultraviolet-optical imaging survey of 38 spiral galaxies within ~20 Mpc. Combined with the PHANGS-ALMA, PHANGS-MUSE surveys and other multiwavelength data, the dataset will provide an unprecedented look into the connections between young stars, HII regions, and cold molecular gas in these nearby star-forming galaxies. Accurate distances are needed to transform measured observables into physical parameters (e.g., brightness to luminosity, angular to physical sizes of molecular clouds, star clusters and associations). PHANGS-HST has obtained parallel ACS imaging of the galaxy ha…
We compare embedded young massive star clusters (YMCs) to (sub-)millimeter line observations tracing the excitation and dissociation of molecular gas in the starburst ring of NGC 1365. This galaxy hosts one of the strongest nuclear starbursts and richest populations of YMCs within 20 Mpc. Here we combine near-/mid-IR PHANGS-JWST imaging with new ALMA multi-J CO (1-0, 2-1 and 4-3) and [CI](1-0) mapping, which we use to trace CO excitation via R42 = I_CO(4-3)/I_CO(2-1) and R21 = I_CO(2-1)/I_CO(1-0) and dissociation via RCICO = I_[CI](1-0)/I_CO(2-1) at 330 pc resolution. We find that the gas flow…
The earliest stages of star formation occur enshrouded in dust and are not observable in the optical. Here we leverage the extraordinary new high-resolution infrared imaging from JWST to begin the study of dust-embedded star clusters in nearby galaxies throughout the local volume. We present a technique for identifying dust-embedded clusters in NGC 7496 (18.7 Mpc), the first galaxy to be observed by the PHANGS-JWST Cycle 1 Treasury Survey. We select sources that have strong 3.3$μ$m PAH emission based on a $\rm F300M-F335M$ color excess, and identify 67 candidate embedded clusters. Only eight o…
We present kinematic orientations and high resolution (150 pc) rotation curves for 67 main sequence star-forming galaxies surveyed in CO (2-1) emission by PHANGS-ALMA. Our measurements are based on the application of a new fitting method tailored to CO velocity fields. Our approach identifies an optimal global orientation as a way to reduce the impact of non-axisymmetric (bar and spiral) features and the uneven spatial sampling characteristic of CO emission in the inner regions of nearby galaxies. The method performs especially well when applied to the large number of independent lines-of-sigh…
The Structure of Molecular Gas in PHANGS-ALMA Galaxies: Cloud Spacing, Two-Point Correlation and Stacked Intensity Profiles
Universität Bonn（波恩大学）；Argelander-Institut für Astronomie, Universität Bonn（波恩大学阿尔加德天体物理研究所）；The Ohio State University（俄亥俄州立大学）；Center for Cosmology and Astroparticle Physics（宇宙学与基本粒子物理中心）；University of Alberta（阿尔伯塔大学）；Université de Toulouse（图卢兹大学）；IRAP（天体物理学研究研究所）；Princeton University（普林斯顿大学）；European Southern Observatory（欧洲南方天文台）；Max-Planck-Institut für extraterrestrische Physik（马克斯·普朗克地外物理研究所）
Molecular Gas Morphological Analogues for the Milky Way
The University of Texas at Austin（德克萨斯大学奥斯汀分校）；INAF-IAPS（意大利国家天体物理研究所国际天体物理中心）；INAF, Sezione di Lecce（意大利国家天体物理研究所莱切分部）；National Astronomical Observatory of Japan（日本国立天文台）；Max Planck Institute for Radio Astronomy（马克斯·普朗克射电天文研究所）；University of Kentucky（肯塔基大学）
JWST/MIRI imaging of the nearby galaxies IC 5332, NGC 628, NGC 1365 and NGC 7496 from PHANGS reveals a richness of gas structures that in each case form a quasi-regular network of interconnected filaments, shells and voids. We examine whether this multi-scale network of structure is consistent with the fragmentation of the gas disk through gravitational instability. We use FilFinder to detect the web of filamentary features in each galaxy and determine their characteristic radial and azimuthal spacings. These spacings are then compared to estimates of the most Toomre-unstable length (a few kpc…
Localized Deviations from the CO-PAH Relation in PHANGS-JWST Galaxies: Faint PAH Emission or Elevated CO Emissivity?
Kavli Institute for Particle Astrophysics & Cosmology (KIPAC), Stanford University（斯坦福大学卡弗里粒子天体物理与宇宙学研究所）；Department of Astronomy, The Ohio State University（俄亥俄州立大学天文学系）；Center for Cosmology and Astroparticle Physics (CCAPP)（宇宙学与高能物理中心）；Department of Astronomy & Astrophysics, University of California, San Diego（加州大学圣地亚哥分校天文与天体物理系）；Sterrenkundig Observatorium, Universiteit Gent（根特大学天文台）；Department of Astronomy, University of Maryland（马里兰大学天文学系）；Observatorio Astronómico Nacional (IGN)（国家天文台（西班牙国家地理研究所））；Max-Planck-Institut für Astronomie（马克斯·普朗克天文学研究所）；Department of Physics, Stanford University（斯坦福大学物理系）
Aims: The complexity of star formation at the physical scale of molecular clouds is not yet fully understood. We investigate the mechanisms regulating the formation of stars in different environments within nearby star-forming galaxies from the PHANGS sample. Methods: Integral field spectroscopic data and radio-interferometric observations of 18 galaxies were combined to explore the existence of the resolved star formation main sequence (rSFMS), resolved Kennicutt-Schmidt relation (rKS), and resolved molecular gas main sequence (rMGMS), and we derived their slope and scatter at spatial resolut…
We use integral field spectroscopy from the PHANGS-MUSE survey, which resolves the ionised interstellar medium at ${\sim}50$ pc resolution in 19 nearby spiral galaxies, to study the origin of the diffuse ionised gas (DIG). We examine the physical conditions of the diffuse gas by first removing morphologically-defined HII regions and then binning the low-surface-brightness areas to achieve significant detections of the key nebular lines. A simple model for the leakage and propagation of ionising radiation from HII regions is able to reproduce the observed distribution of H$α$ in the DIG. Leakin…
Large-scale bars can fuel galaxy centers with molecular gas, often leading to the development of dense ring-like structures where intense star formation occurs, forming a very different environment compared to galactic disks. We pair ~0.3" (30pc) resolution new JWST/MIRI imaging with archival ALMA CO(2-1) mapping of the central ~5kpc of the nearby barred spiral galaxy NGC1365, to investigate the physical mechanisms responsible for this extreme star formation. The molecular gas morphology is resolved into two well-known bright bar lanes that surround a smooth dynamically cold gas disk (R_gal ~ …
Quantifying the decline in CO(2-1) intensity around PHANGS-HST star clusters: Constraints on molecular gas dispersal, stellar feedback, and cluster formation efficiency
Universität Bonn（波恩大学）；University of Cologne（科隆大学）；The Ohio State University（俄亥俄州立大学）；University of Alberta（阿尔伯塔大学）；Space Telescope Science Institute（太空望远镜科学研究所）；The Johns Hopkins University（约翰斯·霍普金斯大学）；University of Wyoming（怀俄明大学）；Université de Toulouse（图卢兹大学）
Ionized nebulae provide critical insights into the conditions of the interstellar medium (ISM). Their bright emission lines enable the measurement of physical properties, such as the gas-phase metallicity, across galaxy disks and in distant galaxies. The PHANGS--MUSE survey has produced optical spectroscopic coverage of the central star-forming discs of 19 nearby main-sequence galaxies. Here, we use the Hα morphology from this data to identify 30,790 distinct nebulae, finding thousands of nebulae per galaxy. For each nebula, we extract emission line fluxes and, using diagnostic line ratios, id…
PHANGS-JWST mid-infrared (MIR) imaging of nearby spiral galaxies has revealed ubiquitous filaments of dust emission in intricate detail. We present a pilot study to systematically map the dust filament network (DFN) at multiple scales between 25-400 pc in NGC 628. MIRI images at 7.7, 10, 11.3 and 21$μ$m of NGC 628 are used to generate maps of the filaments in emission, while PHANGS-HST B-band imaging yields maps of dust attenuation features. We quantify the correspondence between filaments traced by MIR thermal continuum / polycyclic aromatic hydrocarbon (PAH) emission and filaments detected v…
Using PHANGS-HST NUV-U-B-V-I imaging of 17 nearby spiral galaxies, we study samples of star clusters and stellar associations, visually selected to be bright and relatively isolated, for three purposes: to compute aperture corrections for star cluster photometry, to explore the utility of quantitative morphologies in the analysis of clusters and associations, and to compare to synthetic stellar population models. We provide a technical summary of our procedures to determine aperture corrections, a standard step in the production of star cluster candidate catalogs, and compare to prior work. We…
We use PHANGS-JWST data to identify and classify 1271 compact 21 $μ$m sources in four nearby galaxies using MIRI F2100W data. We identify sources using a dendrogram-based algorithm, and we measure the background-subtracted flux densities for JWST bands from 2 $μ$m to 21 $μ$m. Using the SED in JWST as well as HST bands, plus ALMA and MUSE/VLT observations, we classify the sources by eye. Then we use this classification to define regions in color-color space, and so establish a quantitative framework for classifying sources. We identify 1085 sources as belonging to the ISM of the target galaxies…
Ratios of polycyclic aromatic hydrocarbon (PAH) vibrational bands are a promising tool for measuring the properties of the PAH population and their effect on star formation. The photometric bands of the MIRI and NIRCam instruments on JWST provide the opportunity to measure PAH emission features across entire galaxy disks at unprecedented resolution and sensitivity. Here we present the first results of this analysis in a sample of three nearby galaxies: NGC 628, NGC 1365, and NGC 7496. Based on the variations observed in the 3.3, 7.7, and 11.3 $μ$m features, we infer changes to the average PAH …
We compare mid-infrared (mid-IR), extinction-corrected H$α$, and CO (2-1) emission at 70--160 pc resolution in the first four PHANGS-JWST targets. We report correlation strengths, intensity ratios, and power law fits relating emission in JWST's F770W, F1000W, F1130W, and F2100W bands to CO and H$α$. At these scales, CO and H$α$ each correlate strongly with mid-IR emission, and these correlations are each stronger than the one relating CO to H$α$ emission. This reflects that mid-IR emission simultaneously acts as a dust column density tracer, leading to the good match with the molecular gas-tra…
We present the highest resolution CO (2-1) observations obtained to date (0.25") of NGC 3256 and use them to determine the detailed properties of the molecular interstellar medium in the central 6 kpc of this merger. Distributions of physical quantities are reported from pixel-by-pixel measurements at 55 and 120 pc scales and compared to disc galaxies observed by PHANGS-ALMA. Mass surface densities range from 8 to 5500 M$_{\odot}$ pc$^{-2}$ and velocity dispersions from 10 to 200 km s$^{-1}$. Peak brightness temperatures as large as 37 K are measured, indicating the gas in NGC 3256 may be hott…
We measure the low-J CO line ratio R21=CO(2-1)/CO(1-0), R32=CO(3-2)/CO(2-1), and R31 = CO(3-2)/CO(1-0) using whole-disk CO maps of nearby galaxies. We draw CO(2-1) from PHANGS--ALMA, HERACLES, and follow-up IRAM surveys; CO(1-0) from COMING and the Nobeyama CO Atlas of Nearby Spiral Galaxies; and CO(3-2) from the JCMT NGLS and APEX LASMA mapping. Altogether this yields 76, 47, and 29 maps of R21, R32, and R31 at 20" \sim 1.3 kpc resolution, covering 43, 34, and 20 galaxies. Disk galaxies with high stellar mass, log10 M_* [Msun]=10.25-11 and star formation rate, SFR=1-5 Msun/yr, dominate the sa…
