- ID:
- ivo://CDS.VizieR/J/ApJ/703/441
- Title:
- Yellow supergiants in M31
- Short Name:
- J/ApJ/703/441
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The yellow supergiant (F- and G-type) content of nearby galaxies can provide a critical test of stellar evolution theory, bridging the gap between the hot, massive stars and the cool red supergiants. But, this region of the color-magnitude diagram is dominated by foreground contamination, requiring membership to somehow be determined. Fortunately, the large negative systemic velocity of M31, coupled to its high rotation rate, provides the means for separating the contaminating foreground dwarfs from the bona fide yellow supergiants within M31. We obtained radial velocities of ~2900 individual targets within the correct color-magnitude range corresponding to masses of 12M_{sun}_ and higher. A comparison of these velocities to those expected from M31's rotation curve reveals 54 rank-1 (near certain) and 66 rank-2 (probable) yellow supergiant members, indicating a foreground contamination >=96%. We expect some modest contamination from Milky Way halo giants among the remainder, particularly for the rank-2 candidates, and indeed follow-up spectroscopy of a small sample eliminates four rank 2's while confirming five others.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/451/3089
- Title:
- Young clumps embedded in IRDC
- Short Name:
- J/MNRAS/451/3089
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalogue of starless and protostellar clumps associated with infrared dark clouds (IRDCs) in a 40 degrees wide region of the inner Galactic plane (|b|<=1). We have extracted the far-infrared (FIR) counterparts of 3493 IRDCs with known distance in the Galactic longitude range 15<=l<=55 and searched for the young clumps using Herschel infrared Galactic plane survey, the survey of the Galactic plane carried out with the Herschel satellite. Each clump is identified as a compact source detected at 160, 250 and 350um. The clumps have been classified as protostellar or starless, based on their emission (or lack of emission) at 70um. We identify 1723 clumps, 1056 (61%) of which are protostellar and 667 (39%) starless. These clumps are found within 764 different IRDCs, 375 (49%) of which are only associated with protostellar clumps, 178 (23%) only with starless clumps, and 211 (28%) with both categories of clumps. The clumps have a median mass of ~250M_{sun}_ and range up to >10^4^M_{sun}_ in mass and up to 10^5^L_{sun}_ in luminosity. The mass-radius distribution shows that almost 30% of the starless clumps identified in this survey could form high-mass stars; however these massive clumps are confined in only 4% of the IRDCs. Assuming a minimum mass surface density threshold for the formation of high-mass stars, the comparison of the numbers of massive starless clumps and those already containing embedded sources suggests an upper limit lifetime for the starless phase of ~10^5^yr for clumps with a mass M>500M_{sun}_.
- ID:
- ivo://CDS.VizieR/J/A+AS/139/393
- Title:
- Young Massive Star Clusters. II.
- Short Name:
- J/A+AS/139/393
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Table 4 lists photometric data for Young Massive Star Clusters identified in a sample of 21 nearby galaxies. The photometric data have been corrected for Galactic foreground extinction. Each cluster is identified by the abbreviated NGC number of its host galaxy and an object number: nxxx-yyy is object number yyy in the galaxy NGC xxx. Effective cluster radii have been obtained by modeling the cluster images as MOFFAT15 functions convolved with the point-spread function measured on the CCD images.
- ID:
- ivo://CDS.VizieR/J/ApJ/841/92
- Title:
- Young massive star clusters in 2 LEGUS galaxies
- Short Name:
- J/ApJ/841/92
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a study of the effective (half-light) radii and other structural properties of a systematically selected sample of young, massive star clusters (>=5x10^3^M_{sun}_ and <=200Myr) in two nearby spiral galaxies, NGC 628 and NGC 1313. We use Hubble Space Telescope (HST) WFC3/UVIS and archival ACS/WFC data obtained by the Legacy Extragalactic UV Survey (LEGUS), an HST Treasury Program. We measure effective radii with GALFIT, a two- dimensional image-fitting package, and with a new technique to estimate effective radii from the concentration index of observed clusters. The distribution of effective radii from both techniques spans ~0.5-10pc and peaks at 2-3pc for both galaxies. We find slight positive correlations between effective radius and cluster age in both galaxies, but no significant relationship between effective radius and galactocentric distance. Clusters in NGC 1313 display a mild increase in effective radius with cluster mass, but the trend disappears when the sample is divided into age bins. We show that the vast majority of the clusters in both galaxies are much older than their dynamical times, suggesting they are gravitationally bound objects. We find that about half of the clusters in NGC 628 are underfilling their Roche lobes, based on their Jacobi radii. Our results suggest that the young, massive clusters in NGC 628 and NGC 1313 are expanding, due to stellar mass loss or two-body relaxation, and are not significantly influenced by the tidal fields of their host galaxies.
- ID:
- ivo://CDS.VizieR/J/A+A/644/A101
- Title:
- 2403 young stellar groups
- Short Name:
- J/A+A/644/A101
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The purpose of this work is to study the properties of the spatial distribution of the young population in three nearby galaxies in order to better understand the first stages of star formation. We used ACS/HST photometry and the "path-linkage criterion" in order to obtain a catalog of young stellar groups (YSGs) in the galaxy NGC 2403. We studied the internal distribution of stars in these YSGs using the Q parameter. We extended these analyses to the YSGs detected in in NGC 300 and NGC 253 our previous works. We built the young stars' density maps for these three galaxies. Through these maps, we were able to identify and study young stellar structures on larger scales. We found 573 YSGs in the galaxy NGC 2403, for which we derived their individual sizes, densities, luminosity function, and other fundamental characteristics. We find that the vast majority of the YSGs in NGC 2403, NGC 300 and NGC 253 present inner clumpings, following the same hierarchical behavior that we observed in the young stellar structures on larger scales in these galaxies. We derived values of the fractal dimension for these structures between ~1.5 and 1.6. These values are very similar to those obtained in other star forming galaxies and in the interstellar medium, suggesting that the star formation process is regulated by supersonic turbulence.
- ID:
- ivo://CDS.VizieR/J/MNRAS/452/3508
- Title:
- Young stellar structures in NGC 6503
- Short Name:
- J/MNRAS/452/3508
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a detailed clustering analysis of the young stellar population across the star-forming ring galaxy NGC 6503, based on the deep Hubble Space Telescope photometry obtained with the Legacy ExtraGalactic UV Survey. We apply a contour-based map analysis technique and identify in the stellar surface density map 244 distinct star-forming structures at various levels of significance. These stellar complexes are found to be organized in a hierarchical fashion with 95 percent being members of three dominant super-structures located along the star-forming ring. The size distribution of the identified structures and the correlation between their radii and numbers of stellar members show power-law behaviours, as expected from scale-free processes. The self-similar distribution of young stars is further quantified from their autocorrelation function, with a fractal dimension of ~1.7 for length-scales between ~20pc and 2.5kpc. The young stellar radial distribution sets the extent of the star-forming ring at radial distances between 1 and 2.5kpc. About 60 percent of the young stars belong to the detected stellar structures, while the remaining stars are distributed among the complexes, still inside the ring of the galaxy. The analysis of the time-dependent clustering of young populations shows a significant change from a more clustered to a more distributed behaviour in a time-scale of ~60Myr. The observed hierarchy in stellar clustering is consistent with star formation being regulated by turbulence across the ring. The rotational velocity difference between the edges of the ring suggests shear as the driving mechanism for this process. Our findings reveal the interesting case of an inner ring forming stars in a hierarchical fashion.
- ID:
- ivo://CDS.VizieR/J/ApJ/830/10
- Title:
- >20yrs of HST obs. of Cepheids in SNIa host gal.
- Short Name:
- J/ApJ/830/10
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of an optical search conducted as part of the SH0ES project (Supernovae and H_0_ for the Equation of State of dark energy) for Cepheid variable stars using the Hubble Space Telescope (HST) in 19 hosts of Type Ia supernovae (SNe Ia) and the maser-host galaxy NGC4258. The targets include nine newly imaged SN Ia hosts using a novel strategy based on a long-pass filter that minimizes the number of HST orbits required to detect and accurately determine Cepheid properties. We carried out a homogeneous reduction and analysis of all observations, including new universal variability searches in all SNIa hosts, which yielded a total of 2200 variables with well-defined selection criteria, the largest such sample identified outside the Local Group. These objects are used in a companion paper to determine the local value of H_0_ with a total uncertainty of 2.4%.
- ID:
- ivo://CDS.VizieR/J/A+A/625/A94
- Title:
- YSOs in early-type dwarf galaxies
- Short Name:
- J/A+A/625/A94
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- To understand the stellar population content of dwarf early-type galaxies (dEs) and its environmental dependence, we compare the slopes and intrinsic scatter of color-magnitude relations (CMRs) for three nearby clusters, Fornax, Virgo and Coma. Additionally we present and compare internal color profiles of these galaxies to identify central blue regions with younger stars. We use the imaging of the HST/ACS Fornax cluster in the magnitude range of -18:7<=Mg0<=-16:0, to derive magnitudes, colors and color profiles, which we compare with literature measurements from the HST/ACS Virgo and Coma Cluster Survey. We benefit HST accuracy to investigate and parameterize the (g'-z') color profiles of these dEs. Based on analysis of the color profiles, we report a large number of dEs with young stellar populations in their center in all three clusters. While for Virgo and Coma the number of blue-cored dEs is found to be 85%+/-2% and 53%+/-3% respectively, for Fornax, we find that all galaxies have a blue core.We show that bluer cores reside in fainter dEs, similar to the trend seen in nucleated dEs. We find no correlation between the luminosity of the galaxy and the size of its blue core. Moreover, a comparison of the CMRs of the three clusters shows that the scatter in Virgo's CMR is considerably larger than in the Fornax and Coma clusters. Presenting adaptive smoothing we show that the galaxies on the blue side of the CMR often show evidence for dust extinction, which strengthens the interpretation that the bluer colors are due to young stellar populations. We also find that outliers on the red side of the CMR are more compact than expected for their luminosity. We find several of these red outliers in Virgo, often close to more massive galaxies. No red outlying compact early-types are found in Fornax and Coma in this magnitude range while we find three in the Virgo cluster. We show that the CMR of the Fornax and Virgo clusters are slightly bluer than that of Coma. We suggest that the large number of outliers and larger scatter found for the Virgo cluster CMR is a result of Virgos different assembly history.
- ID:
- ivo://CDS.VizieR/J/ApJ/813/78
- Title:
- z=4.5 and z=5.7 LAEs properties with Spitzer
- Short Name:
- J/ApJ/813/78
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results from a stellar population modeling analysis of a sample of 162 z=4.5 and 14 z=5.7 Ly{alpha} emitting galaxies (LAEs) in the Bootes field, using deep Spitzer/IRAC data at 3.6 and 4.5 {mu}m from the Spitzer Ly{alpha} Survey, along with Hubble Space Telescope NICMOS and WFC3 imaging at 1.1 and 1.6 {mu}m for a subset of the LAEs. This represents one of the largest samples of high-redshift LAEs imaged with Spitzer IRAC. We find that 30/162 (19%) of the z=4.5 LAEs and 9/14 (64%) of the z=5.7 LAEs are detected at >=3{sigma} in at least one IRAC band. Individual z=4.5 IRAC-detected LAEs have a large range of stellar mass, from 5x10^8^-10^11^ M_{sun}_. One-third of the IRAC-detected LAEs have older stellar population ages of 100 Myr^-1^ Gyr, while the remainder have ages <100 Myr. A stacking analysis of IRAC-undetected LAEs shows this population to be primarily low mass (8-20x10^8^ M_{sun}_) and young (64-570 Myr). We find a correlation between stellar mass and the dust-corrected ultraviolet-based star formation rate (SFR) similar to that at lower redshifts, in that higher mass galaxies exhibit higher SFRs. However, the z=4.5 LAE correlation is elevated 4-5 times in SFR compared to continuum-selected galaxies at similar redshifts. The exception is the most massive LAEs which have SFRs similar to galaxies at lower redshifts suggesting that they may represent a different population of galaxies than the traditional lower-mass LAEs, perhaps with a different mechanism promoting Ly{alpha} photon escape.
- ID:
- ivo://CDS.VizieR/J/MNRAS/379/1546
- Title:
- z'BVRi' photometry of ClG 0016+1609
- Short Name:
- J/MNRAS/379/1546
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report a definitive confirmation of a large-scale structure around the super rich cluster CL0016+1609 at z=0.55. We made spectroscopic follow-up observations with Faint Object Camera and Spectrograph (FOCAS) on Subaru along the large filamentary structure identified in our previous photometric studies, including some subclumps already found by other authors.
