- ID:
- ivo://CDS.VizieR/J/MNRAS/451/3173
- Title:
- Circumnuclear star-forming regions
- Short Name:
- J/MNRAS/451/3173
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present photometry in U, B, V, R and I continuum bands and in H{alpha} and H{beta} emission lines for a sample of 336 circumnuclear star-forming regions located in early-type spiral galaxies with different levels of activity in their nuclei. They are nearby galaxies, with distances less than 100Mpc, 60 per cent of which are considered as interacting objects. This survey of 20 nuclear rings aims to provide insight into their star formation properties as age, stellar population and star formation rate. Extinction-corrected H{alpha} luminosities range from 1.3x10^38^ to 4x10^41^erg/s, with most of the regions showing values between 39.5<=logL_H{alpha}_<=40, which implies masses for the ionizing clusters higher than 2x10^5^M_{sun}_. H{alpha} and H{beta} images have allowed us to obtain an accurate measure of extinction. We have found an average value of A_V_=1.85 mag. (U-B) colour follows a two maximum distribution around (U-B)=~-0.7, and -0.3; (R-I) also presents a bimodal behaviour, with maximum values of 0.6 and 0.9. Reddest (U-B) and (R-I) regions appear in non-interacting galaxies. Reddest (R-I) regions lie in strongly barred galaxies. For a significant number of HII regions, the observed colours and equivalent widths are not well reproduced by single burst evolutionary theoretical models.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/449/574
- Title:
- Circumstellar discs at white dwarfs
- Short Name:
- J/MNRAS/449/574
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- White dwarfs whose atmospheres are polluted by terrestrial-like planetary debris have become a powerful and unique tool to study evolved planetary systems. This paper presents results for an unbiased Spitzer Infrared Array Camera search for circumstellar dust orbiting a homogeneous and well-defined sample of 134 single white dwarfs. The stars were selected without regard to atmospheric metal content but were chosen to have (1) hydrogen-rich atmospheres, (2) 17000<Teff<25000K and correspondingly young post-main-sequence ages of 15-270Myr, and (3) sufficient far-ultraviolet brightness for a corresponding Hubble Space Telescope COS snapshot. Five white dwarfs were found to host an infrared bright dust disc, three previously known, and two reported here for the first time, yielding a nominal 3.7^+2.4^_-1.0_ percent of white dwarfs in this post-main-sequence age range with detectable circumstellar dust. Remarkably, the complementary Hubble observations indicate that a fraction of 27 percent show metals in their photosphere that can only be explained with ongoing accretion from circumstellar material, indicating that nearly 90 percent of discs escape detection in the infrared, likely due to small emitting surface area. This paper also presents the distribution of disc fractional luminosity as a function of cooling age for all known dusty white dwarfs, suggesting possible disc evolution scenarios and indicating an undetected population of circumstellar discs.
- ID:
- ivo://CDS.VizieR/J/AJ/119/3026
- Title:
- Circumstellar disk candidates in Orion
- Short Name:
- J/AJ/119/3026
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an optical study of four 45'x45' fields centered ~0.5{deg} east, west, north, and south of the Orion Nebula Cluster center. We have measured V and I_C_ photometry for ~5000 stars, and U photometry for ~1600 of these. We have obtained spectral classifications for ~300 of the stars with UVI_C_ photometry plus an additional ~200 stars located outside the area of our photometric survey. Dereddened photometry allows us to investigate the evidence for circumstellar accretion disks from excess emission at ultraviolet wavelengths, as well as the mass and age distributions of our sample. We find ~230 active accretion disk candidates and estimate the accretion disk fraction at >~40%. We use the magnitude of the ultraviolet excess to infer disk accretion rates. The mass accretion rate (dM/dt) decreases slowly with age over the limited age range spanned by our data, 1-3Myr, and increases slowly with mass over the limited mass range 0.2-1.2 M_{sun}_.
- ID:
- ivo://CDS.VizieR/J/AJ/135/966
- Title:
- Circumstellar disk evolution in NGC 2068/71
- Short Name:
- J/AJ/135/966
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the disk and accretion properties of young stars in the NGC 2068 and NGC 2071 clusters. Using low-resolution optical spectra, we define a membership sample and determine an age for the region of ~2Myr. Using high-resolution spectra of the H{alpha} line we study the accretion activity of these likely members and also examine the disk properties of the likely members using IRAC and MIPS mid-infrared photometry. A substantial fraction (79%) of the 67 members have an infrared excess while all of the stars with significant infrared excess show evidence for active accretion. We find three populations of evolved disks (IRAC weak, MIPS weak, and transition disks) all of which show decreased accretion activity in addition to the evidence for evolution in the dust disk.
- ID:
- ivo://CDS.VizieR/J/ApJ/784/62
- Title:
- Circumstellar disks around binary stars in Taurus
- Short Name:
- J/ApJ/784/62
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have conducted a survey of 17 wide (>100 AU) young binary systems in Taurus with the Atacama Large Millimeter Array (ALMA) at two wavelengths. The observations were designed to measure the masses of circumstellar disks in these systems as an aid to understanding the role of multiplicity in star and planet formation. The ALMA observations had sufficient resolution to localize emission within the binary system. Disk emission was detected around all primaries and 10 secondaries, with disk masses as low as 10^-4^ M_{sun}_. We compare the properties of our sample to the population of known disks in Taurus and find that the disks from this binary sample match the scaling between stellar mass and millimeter flux of F_mm_ \propto M_*_^1.5-2.0^ to within the scatter found in previous studies. We also compare the properties of the primaries to those of the secondaries and find that the secondary/primary stellar and disk mass ratios are not correlated; in three systems, the circumsecondary disk is more massive than the circumprimary disk, counter to some theoretical predictions.
- ID:
- ivo://CDS.VizieR/J/AJ/156/75
- Title:
- Circumstellar disks in the Upper Sco association
- Short Name:
- J/AJ/156/75
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have performed a survey for new members of the Upper Sco association that have circumstellar disks using mid-infrared photometry from the Wide-field Infrared Survey Explorer (WISE). Through optical and near-infrared spectroscopy, we have confirmed 185 candidates as likely members of Upper Sco with spectral types ranging from mid-K to M9. They comprise ~36% of the known disk-bearing members of the association. We also have compiled all available mid-infrared photometry from WISE and the Spitzer Space Telescope for the known members of Upper Sco, resulting in a catalog of data for 1608 objects. We have used these data to identify the members that exhibit excess emission from disks and we have classified the evolutionary stages of those disks with criteria similar to those applied in our previous studies of Taurus and Upper Sco. Among 484 members with excesses in at least one band (excluding five Be stars), we classify 296 disks as full, 66 as evolved, 19 as transitional, 22 as evolved or transitional, and 81 as evolved transitional or debris. Many of these disks have not been previously reported, including 129 full disks and 50 disks that are at more advanced evolutionary stages.
- ID:
- ivo://CDS.VizieR/J/AJ/160/24
- Title:
- Circumstellar dust of 104 stars with GPIES
- Short Name:
- J/AJ/160/24
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the results of a ~4yr direct imaging survey of 104 stars to resolve and characterize circumstellar debris disks in scattered light as part of the Gemini Planet Imager (GPI) Exoplanet Survey. We targeted nearby (<~150pc), young (<~500Myr) stars with high infrared (IR) excesses (LIR/L_{star}_>10^-5^), including 38 with previously resolved disks. Observations were made using the GPI high-contrast integral field spectrograph in H-band (1.6{mu}m) coronagraphic polarimetry mode to measure both polarized and total intensities. We resolved 26 debris disks and 3 protoplanetary/transitional disks. Seven debris disks were resolved in scattered light for the first time, including newly presented HD117214 and HD156623, and we quantified basic morphologies of five of them using radiative transfer models. All of our detected debris disks except HD156623 have dust-poor inner holes, and their scattered-light radii are generally larger than corresponding radii measured from resolved thermal emission and those inferred from spectral energy distributions. To assess sensitivity, we report contrasts and consider causes of nondetections. Detections were strongly correlated with high IR excess and high inclination, although polarimetry outperformed total intensity angular differential imaging for detecting low-inclination disks (<~70{deg}). Based on postsurvey statistics, we improved upon our presurvey target prioritization metric predicting polarimetric disk detectability. We also examined scattered-light disks in the contexts of gas, far-IR, and millimeter detections. Comparing H-band and ALMA fluxes for two disks revealed tentative evidence for differing grain properties. Finally, we found no preference for debris disks to be detected in scattered light if wide-separation substellar companions were present.
- ID:
- ivo://CDS.VizieR/J/A+A/580/A131
- Title:
- Circumstellar-interacting supernovae
- Short Name:
- J/A+A/580/A131
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Some circumstellar-interacting (CSI) supernovae (SNe) are produced by the explosions of massive stars that have lost mass shortly before the SN explosion. There is evidence that the precursors of some SNe IIn were luminous blue variable (LBV) stars. For a small number of CSI SNe, outbursts have been observed before the SN explosion. Eruptive events of massive stars are named SN impostors (SN IMs) and whether they herald a forthcoming SN or not is still unclear. The large variety of observational properties of CSI SNe suggests the existence of other progenitors, such as red supergiant (RSG) stars with superwinds. Furthermore, the role of metallicity in the mass loss of CSI SN progenitors is still largely unexplored. Our goal is to gain insight into the nature of the progenitor stars of CSI SNe by studying their environments, in particular the metallicity at their locations. We obtain metallicity measurements at the location of 60 transients (including SNe IIn, SNe Ibn, and SN IMs) via emission-line diagnostic on optical spectra obtained at the Nordic Optical Telescope and through public archives. Metallicity values from the literature complement our sample. We compare the metallicity distributions among the different CSI SN subtypes, and to those of other core-collapse SN types. We also search for possible correlations between metallicity and CSI SN observational properties. We find that SN IMs tend to occur in environments with lower metallicity than those of SNe IIn. Among SNe IIn, SN IIn-L(1998S-like) SNe show higher metallicities, similar to those of SNe IIL/P, whereas long-lasting SNe IIn (1988Z-like) show lower metallicities, similar to those of SN IMs. The metallicity distribution of SNe IIn can be reproduced by combining the metallicity distributions of SN IMs (which may be produced by major outbursts of massive stars like LBVs) and SNe IIP (produced by RSGs). The same applies to the distributions of the normalized cumulative rank (NCR) values, which quantifies the SN association to HII regions. For SNe IIn, we find larger mass-loss rates and higher CSM velocities at higher metallicities. The luminosity increment in the optical bands during SN IM outbursts tend to be larger at higher metallicity, whereas the SN IM quiescent optical luminosities tend to be lower. The difference in metallicity between SNe IIn and SN IMs indicates that LBVs are only one of the progenitor channels for SNe IIn, with 1988Z-like and 1998S-like SNe possibly arising from LBVs and RSGs, respectively. Finally, even though line-driven winds likely do not primarily drive the late mass-loss of CSI SN progenitors, metallicity has some impact on the observational properties of these transients.
- ID:
- ivo://CDS.VizieR/J/A+A/310/933
- Title:
- C isotopic ratio in N- and SC-type stars
- Short Name:
- J/A+A/310/933
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a result of quantitative analysis of ^12^C/^13^C ratios in 62 N-type and 15 SC-type carbon stars. By the use of CCD as a detector we can obtain spectra of resolution ~20,000 with enough signal-to-noise ratios for a large number of carbon stars, for which ^12^C/^13^C ratios have not yet been derived. Carbon isotopic ratios are determined from lines of the CN red system around 8000A, based on the iso-intensity method and line-blanketed model atmospheres. The average of ^12^C/^13^C ratios in 62 N-type carbon stars is found to be 27+/-11 (standard deviation). The majority of the N-type carbon stars studied (about 85%) are found to have ^12^C/^13^C ratios less than 40, and the number of stars which have ^12^C/^13^C ratios larger than 40 is found to be relatively small. This result shows a marked contrast to some of the previous results that have shown the opposite distribution, namely, ^12^C/^13^C ratios mostly larger than 40 in N-type carbon stars. The average of ^12^C/^13^C ratios in 15 SC-type carbon stars is found to be 22+/-14 (standard deviation). Most of the SC-type carbon stars studied are found to have ^12^C/^13^C ratios larger than 10, while only three of them turn out to be ^13^C-rich. This is in contrast with the earlier classification based on low resolution spectra which classified them as J-type, that is, ^13^C-rich. The earlier temperature scale which classified SC-type carbon stars as the latest (C8-9) based on their strong NaI D lines can not be necessarily justified. The strong NaI D lines of SC stars should be attributed to the peculiar atmospheric structure due to C/O ratios very near to unity. The resulting ^12^C/^13^C ratios are partly consistent with the scenario in which M giants evolve through SC-type to N-type carbon stars, as ^12^C produced during the helium shell flash is added to the envelope.
- ID:
- ivo://CDS.VizieR/J/ApJ/671/1503
- Title:
- Cl 0024+16 and MS 0451-03 spectrophotometry
- Short Name:
- J/ApJ/671/1503
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new results from our comparative survey of two massive, intermediate-redshift galaxy clusters, Cl 0024+17 (z=0.39) and MS 0451-03 (z=0.54). Combining optical and UV imaging with spectroscopy of member galaxies, we identify and study several key classes of "transition objects" whose stellar populations or dynamical states indicate a recent change in morphology and star formation rate. For the first time, we have been able to conclusively identify spiral galaxies in the process of transforming into S0 galaxies. This has been accomplished by locating both spirals whose star formation is being quenched and their eventual successors, the recently created S0s.
