- ID:
- ivo://CDS.VizieR/J/A+A/658/A188
- Title:
- PHANGS-MUSE sample HII regions catalog
- Short Name:
- J/A+A/658/A188
- Date:
- 02 Mar 2022 06:10:18
- Publisher:
- CDS
- Description:
- We use an unprecedented sample of about 23000 HII regions detected at an average physical resolution of 67pc in the PHANGS-MUSE sample to study the extragalactic HII region H{alpha} luminosity function (LF). Our observations probe the star-forming disk of 19 nearby spiral galaxies with low inclination and located close to the star formation main sequence at z=0. The mean LF slope in our sample is =1.73 with a {sigma} of 0.15. We find that {alpha} decreases with the galaxy's star formation rate surface density {SIGMA}_SFR_ and argue that this is driven by an enhanced clustering of young stars at high gas surface densities. Looking at the HII regions within single galaxies we find that no significant variations occur between the LF of the inner and outer part of the star-forming disk, whereas the LF in the spiral arm areas is shallower than in the inter-arm areas for six out of the 13 galaxies with clearly visible spiral arms. We attribute these variations to the spiral arms increasing the molecular clouds arm-inter-arm mass contrast and find suggestive evidence that they are more evident for galaxies with stronger spiral arms. Furthermore, we find systematic variations in {alpha} between samples of HII regions with high and low ionization parameter q and argue that they are driven by the aging of HII regions.
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- ID:
- ivo://CDS.VizieR/J/ApJ/802/127
- Title:
- PHAT stellar cluster survey. II. AP catalog
- Short Name:
- J/ApJ/802/127
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We construct a stellar cluster catalog for the Panchromatic Hubble Andromeda Treasury (PHAT) survey using image classifications collected from the Andromeda Project (AP) citizen science website. We identify 2753 clusters and 2270 background galaxies within ~0.5deg^2^ of PHAT imaging searched, or ~400kpc^2^ in deprojected area at the distance of the Andromeda Galaxy (M31). These identifications result from 1.82million classifications of ~20000 individual images (totaling ~7gigapixels) by tens of thousands of volunteers. We show that our crowd-sourced approach, which collects >80 classifications per image, provides a robust, repeatable method of cluster identification. The high spatial resolution Hubble Space Telescope images resolve individual stars in each cluster and are instrumental in the factor of ~6 increase in the number of clusters known within the survey footprint. We measure integrated photometry in six filter passbands, ranging from the near-UV to the near-IR. PHAT clusters span a range of ~8 magnitudes in F475W (g-band) luminosity, equivalent to ~4 decades in cluster mass. We perform catalog completeness analysis using >3000 synthetic cluster simulations to determine robust detection limits and demonstrate that the catalog is 50% complete down to ~500M_{sun}_ for ages <100Myr. We include catalogs of clusters, background galaxies, remaining unselected candidates, and synthetic cluster simulations, making all information publicly available to the community. The catalog published here serves as the definitive base data product for PHAT cluster science, providing a census of star clusters in an L^*^ spiral galaxy with unmatched sensitivity and quality.
- ID:
- ivo://CDS.VizieR/J/ApJ/752/95
- Title:
- PHAT stellar cluster survey. I. Year 1
- Short Name:
- J/ApJ/752/95
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Panchromatic Hubble Andromeda Treasury (PHAT) survey is an ongoing Hubble Space Telescope (HST) multi-cycle program to obtain high spatial resolution imaging of one-third of the M31 disk at ultraviolet through near-infrared wavelengths. In this paper, we present the first installment of the PHAT stellar cluster catalog. When completed, the PHAT cluster catalog will be among the largest and most comprehensive surveys of resolved star clusters in any galaxy. The exquisite spatial resolution achieved with HST has allowed us to identify hundreds of new clusters that were previously inaccessible with existing ground-based surveys. We identify 601 clusters in the Year 1 sample, representing more than a factor of four increase over previous catalogs within the current survey area (390 arcmin^2^). This work presents results derived from the first ~25% of the survey data; we estimate that the final sample will include ~2500 clusters. For the Year 1 objects, we present a catalog with positions, radii, and six-band integrated photometry. Along with a general characterization of the cluster luminosities and colors, we discuss the cluster luminosity function, the cluster size distributions, and highlight a number of individually interesting clusters found in the Year 1 search.
- ID:
- ivo://CDS.VizieR/J/MNRAS/451/724
- Title:
- PHAT. XIII. M31 Cepheid P-L relation
- Short Name:
- J/MNRAS/451/724
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using Hubble Space Telescope Advanced Camera for Surveys (HST/ACS) and Wide Field Camera 3 (WFC3) observations from the Panchromatic Hubble Andromeda Treasury (PHAT), we present new period-luminosity (P-L) relations for Cepheid variables in M31. Cepheids from several ground-based studies are identified in the PHAT photometry to derive new P-L and Wesenheit P-L relations in the near infrared and visual filters. We derive a distance modulus to M31 of 24.51+/-0.08 in the IR bands and 24.32+/-0.09 in the visual bands, including the first P-L relations in the F_475W_ and F_814W_ filters for M31. Our derived visual and IR distance moduli disagree at slightly more than a 1{sigma} level. Differences in the P-L relations between ground-based and HST observations are investigated for a subset of Cepheids. We find a significant discrepancy between ground-based and HST P-L relations with the same Cepheids, suggesting adverse effects from photometric contamination in ground-based Cepheid observations. Additionally, a statistically significant radial trend in the P-L relation is found which does not appear to be explained by metallicity.
- ID:
- ivo://CDS.VizieR/J/ApJ/846/145
- Title:
- PHAT. XIX. Formation history of M31 disk
- Short Name:
- J/ApJ/846/145
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We map the star formation history across M31 by fitting stellar evolution models to color-magnitude diagrams of each 83"x83" (0.3x1.4kpc, deprojected) region of the Panchromatic Hubble Andromeda Treasury (PHAT) survey outside of the innermost 6'x12' portion. We find that most of the star formation occurred prior to ~8Gyr ago, followed by a relatively quiescent period until ~4Gyr ago, a subsequent star formation episode about 2Gyr ago, and a return to relative quiescence. There appears to be little, if any, structure visible for populations with ages older than 2Gyr, suggesting significant mixing since that epoch. Finally, assuming a Kroupa initial mass function from 0.1 to 100M_{sun}_, we find that the total amount of star formation over the past 14Gyr in the area over which we have fit models is 5x10^10^M_{sun}_. Fitting the radial distribution of this star formation and assuming azimuthal symmetry, (1.5+/-0.2)x10^11^M_{sun}_ of stars has formed in the M31 disk as a whole, (9+/-2)x10^10^M_{sun}_ of which has likely survived to the present after accounting for evolutionary effects. This mass is about one-fifth of the total dynamical mass of M31.
- ID:
- ivo://CDS.VizieR/J/ApJS/215/9
- Title:
- PHAT X. UV-IR photometry of M31 stars
- Short Name:
- J/ApJS/215/9
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have measured stellar photometry with the Hubble Space Telescope Wide Field Camera 3 (WFC3) and Advanced Camera for Surveys in near ultraviolet (F275W, F336W), optical (F475W, F814W), and near infrared (F110W, F160W) bands for 117 million resolved stars in M31. As part of the Panchromatic Hubble Andromeda Treasury survey, we measured photometry with simultaneous point-spread function (PSF) fitting across all bands and at all source positions after precise astrometric image alignment (<5-10mas accuracy). In the outer disk, the photometry reaches a completeness-limited depth of F475W~28, while in the crowded, high surface brightness bulge, the photometry reaches F475W~25. We find that simultaneous photometry and optimized measurement parameters significantly increase the detection limit of the lowest-resolution filters (WFC3/IR) providing color-magnitude diagrams (CMDs) that are up to 2.5mag deeper when compared with CMDs from WFC3/IR photometry alone. We present extensive analysis of the data quality including comparisons of luminosity functions and repeat measurements, and we use artificial star tests to quantify photometric completeness, uncertainties and biases. We find that the largest sources of systematic error in the photometry are due to spatial variations in the PSF models and charge transfer efficiency corrections.
- ID:
- ivo://CDS.VizieR/J/ApJ/827/33
- Title:
- PHAT. XVI. Star cluster masses and ages
- Short Name:
- J/ApJ/827/33
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use the Panchromatic Hubble Andromeda Treasury survey data set to perform spatially resolved measurements of star cluster formation efficiency ({Gamma}), the fraction of stellar mass formed in long-lived star clusters. We use robust star formation history and cluster parameter constraints, obtained through color-magnitude diagram analysis of resolved stellar populations, to study Andromeda's cluster and field populations over the last ~300Myr. We measure {Gamma} of 4%-8% for young, 10-100Myr-old populations in M31. We find that cluster formation efficiency varies systematically across the M31 disk, consistent with variations in mid-plane pressure. These {Gamma} measurements expand the range of well-studied galactic environments, providing precise constraints in an HI-dominated, low-intensity star formation environment. Spatially resolved results from M31 are broadly consistent with previous trends observed on galaxy-integrated scales, where {Gamma} increases with increasing star formation rate surface density ({Sigma}_SFR_). However, we can explain observed scatter in the relation and attain better agreement between observations and theoretical models if we account for environmental variations in gas depletion time ({tau}_dep_) when modeling {Gamma}, accounting for the qualitative shift in star formation behavior when transitioning from a H_2_-dominated to a HI-dominated interstellar medium. We also demonstrate that {Gamma} measurements in high {Sigma}_SFR_ starburst systems are well-explained by {tau}_dep_-dependent fiducial {Gamma} models.
- ID:
- ivo://CDS.VizieR/J/ApJ/768/74
- Title:
- PHIBSS: CO observations of star-forming galaxies
- Short Name:
- J/ApJ/768/74
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present PHIBSS, the IRAM Plateau de Bure high-z blue sequence CO(3-2) survey of the molecular gas properties in massive, main-sequence star-forming galaxies (SFGs) near the cosmic star formation peak. PHIBSS provides 52 CO detections in two redshift slices at z~1.2 and 2.2, with log(M_*_(M_{sun}_))>=10.4 and log(SFR(M_{sun}_/yr))>=1.5. Including a correction for the incomplete coverage of the M_*_-SFR plane, and adopting a "Galactic" value for the CO-H_2_ conversion factor, we infer average gas fractions of ~0.33 at z~1.2 and ~0.47 at z~2.2. Gas fractions drop with stellar mass, in agreement with cosmological simulations including strong star formation feedback. Most of the z~1-3 SFGs are rotationally supported turbulent disks. The sizes of CO and UV/optical emission are comparable. The molecular-gas-star-formation relation for the z=1-3 SFGs is near-linear, with a ~0.7Gyr gas depletion timescale; changes in depletion time are only a secondary effect. Since this timescale is much less than the Hubble time in all SFGs between z~0 and 2, fresh gas must be supplied with a fairly high duty cycle over several billion years. At given z and M_*_, gas fractions correlate strongly with the specific star formation rate (sSFR). The variation of sSFR between z~0 and 3 is mainly controlled by the fraction of baryonic mass that resides in cold gas.
- ID:
- ivo://CDS.VizieR/J/AJ/125/465
- Title:
- Phoenix Deep Survey 1.4-GHz microJy Catalog
- Short Name:
- J/AJ/125/465
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The initial Phoenix Deep Survey (PDS) observations with the Australia Telescope Compact Array have been supplemented by additional 1.4 GHz observations over the past few years. Here we present details of the construction of a new mosaic image covering an area of 4.56 deg2, an investigation of the reliability of the source measurements, and the 1.4 GHz source counts for the compiled radio catalog. The mosaic achieves a 1-sigma rms noise of 12 microJy at its most sensitive, and a homogeneous radio-selected catalog of over 2000 sources reaching flux densities as faint as 60 microJy has been compiled. The source parameter measurements are found to be consistent with the expected uncertainties from the image noise levels and the Gaussian source fitting procedure. A radio-selected sample avoids the complications of obscuration associated with optically selected samples, and by utilizing complementary PDS observations, including multicolor optical, near-infrared, and spectroscopic data, this radio catalog will be used in a detailed investigation of the evolution in star formation spanning the redshift range 0 < z < 1. The homogeneity of the catalog ensures a consistent picture of galaxy evolution can be developed over the full cosmologically significant redshift range of interest.
- ID:
- ivo://CDS.VizieR/J/ApJS/155/1
- Title:
- Phoenix Deep Survey: optical and NIR catalogs
- Short Name:
- J/ApJS/155/1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Phoenix Deep Survey is a multiwavelength galaxy survey based on deep 1.4GHz radio imaging. The primary goal of this survey is to investigate the properties of star formation in galaxies and to trace the evolution in those properties to a redshift z=1, covering a significant fraction of the age of the universe. By compiling a sample of star-forming galaxies based on selection at radio wavelengths we eliminate possible biases due to dust obscuration, a significant issue when selecting objects at optical and ultraviolet wavelengths. In this paper, we present the catalogs and results of deep optical (UBVRI) and near-infrared (Ks) imaging of the deepest region of the existing decimetric radio imaging. The observations and data processing are summarized and the construction of the optical source catalogs described, together with the details of the identification of candidate optical counterparts to the radio catalogs. Based on our UBVRIKs imaging, photometric redshift estimates for the optical counterparts to the radio detections are explored.
