- ID:
- ivo://CDS.VizieR/J/MNRAS/508/1084
- Title:
- MaNGA star-forming galaxies
- Short Name:
- J/MNRAS/508/1084
- Date:
- 19 Jan 2022 00:58:55
- Publisher:
- CDS
- Description:
- We investigate radiation hardness within a representative sample of 67 nearby (0.02<~z<~0.06) star-forming (SF) galaxies using the integral field spectroscopic data from the MaNGA survey. The softness parameter {eta}=(O^+^/O^2+^)/(S^+^/S^2+^) is sensitive to the spectral energy distribution of the ionizing radiation. We study {eta} via the observable quantity {eta}'(=([OII]/[OIII])/([SII][SIII])). We analyze the relation between radiation hardness (traced by {eta} and {eta}') and diagnostics sensitive to gas-phase metallicity, electron temperature, density, ionization parameter, effective temperature, and age of ionizing populations. It is evident that low metallicity is accompanied by low log{eta}', i.e. hard radiation field. No direct relation is found between radiation hardness and other nebular parameters though such relations cannot be ruled out. We provide empirical relations between log{eta} and strong emission line ratios N2, O3N2, and Ar3O3, which will allow future studies of radiation hardness in SF galaxies where weak auroral lines are undetected. We compare the variation of [OIII]/[OII] and [SIII]/[SII] for MaNGA data with SF galaxies and HII regions within spiral galaxies from literature and find that the similarity and differences between different data set are mainly due to the metallicity. We find that predictions from photoionization models considering young and evolved stellar populations as ionizing sources in good agreement with the MaNGA data. This comparison also suggests that hard radiation fields from hot and old low-mass stars within or around SF regions might significantly contribute to the observed {eta} values.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/570/A82
- Title:
- Mapping accretion variability in NGC 2264
- Short Name:
- J/A+A/570/A82
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Our study aims at characterizing the accretion properties of several hundred members of the star-forming region NGC 2264 (3Myr). We performed a deep u,g,r,i mapping of the cluster with CFHT/MegaCam, and monitored the simultaneous u+r variability of its members over a baseline of two weeks. Stellar parameters are determined homogeneously for about 750 monitored young objects, 40% of which are accreting T Tauri stars. Accretion properties and accretion variability are investigated and characterized from UV excess measurements. Non-accreting members of the cluster define the reference UV emission level over which flux excess is detected and measured.
- ID:
- ivo://CDS.VizieR/V/127A
- Title:
- MASH Catalogues of Planetary Nebulae
- Short Name:
- V/127A
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Macquarie/AAO/Strasbourg H{alpha} Planetary Nebula Catalogue (MASH) contains 903 new true, likely and possible Galactic Planetary Nebulae (PNe) discovered from the AAO/UKST H{alpha} survey of the southern Galactic plane. The combination of depth, resolution, uniformity, and areal coverage of the H {alpha}survey has opened up an hitherto unexplored region of parameter space permitting the detection of this significant new PN sample. This catalogue includes also the spectra of the PNe as FITS files (in the "sp" subdirectory), and a gallery of images created as a combination of the H{alpha} and short red images of the survey. The second part, MASH-II (table mash2.dat) consists of over 300 true, likely and possible new Galactic PNe found after re-examination of the entire AAO/UKST H{alpha} survey of the Southern Galactic Plane in digital form. Over 240 of these new candidates were confirmed as bona fide PNe on the basis of spectroscopic observations. The spectra of this supplement will be available in the future.
- ID:
- ivo://CDS.VizieR/J/ApJ/767/14
- Title:
- MASIV survey III. Optical identifications
- Short Name:
- J/ApJ/767/14
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Intraday variability (IDV) of the radio emission from active galactic nuclei is now known to be predominantly due to interstellar scintillation (ISS). The MASIV (The Micro-Arcsecond Scintillation-Induced Variability) survey of 443 flat spectrum sources revealed that the IDV is related to the radio flux density and redshift. A study of the physical properties of these sources has been severely handicapped by the absence of reliable redshift measurements for many of these objects. This paper presents 79 new redshifts and a critical evaluation of 233 redshifts obtained from the literature. We classify spectroscopic identifications based on emission line properties, finding that 78% of the sources have broad emission lines and are mainly FSRQs. About 16% are weak lined objects, chiefly BL Lacs, and the remaining 6% are narrow line objects. The gross properties (redshift, spectroscopic class) of the MASIV sample are similar to those of other blazar surveys. However, the extreme compactness implied by ISS favors FSRQs and BL Lacs in the MASIV sample as these are the most compact object classes. We confirm that the level of IDV depends on the 5GHz flux density for all optical spectral types. We find that BL Lac objects tend to be more variable than broad line quasars. The level of ISS decreases substantially above a redshift of about two. The decrease is found to be generally consistent with ISS expected for beamed emission from a jet that is limited to a fixed maximum brightness temperature in the source rest frame.
- ID:
- ivo://CDS.VizieR/J/ApJ/875/51
- Title:
- Mass accretion rates of PMS stars. VI. LH95 in LMC
- Short Name:
- J/ApJ/875/51
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on the accretion properties of low-mass stars in the LH 95 association within the Large Magellanic Cloud. Using noncontemporaneous wideband optical and narrowband H{alpha} photometry obtained with the Hubble Space Telescope, we identify 245 low-mass pre-main-sequence (PMS) candidates showing H{alpha} excess emission above the 4{sigma} level. We derive their physical parameters, including effective temperatures, luminosities, masses (M_*_), ages, accretion luminosities, and mass accretion rates (dM/dt_acc_). We identify two different stellar populations: younger than ~8Myr with median dM/dt_acc_~5.4x10^-8^M_{sun}_/yr (and M_*_~0.15-1.8M_{sun}_) and older than ~8Myr with median dM/dt_acc_~4.8x10^-9^M_{sun}_/yr (and M_*_~0.6-1.2M_{sun}_). We find that the younger PMS candidates are assembled in groups around Be stars, while older PMS candidates are uniformly distributed within the region without evidence of clustering. We find that dM/dt_acc_ in LH 95 decreases with time more slowly than what is observed in Galactic star-forming regions (SFRs). This agrees with the recent interpretation, according to which higher metallicity limits the accretion process in both rate and duration due to higher radiation pressure. The dM/dt_acc_-M_*_ relationship shows different behavior at different ages, becoming progressively steeper at older ages, indicating that the effects of mass and age on dM/dt_acc_ cannot be treated independently. With the aim to identify reliable correlations between mass, age, and dM/dt_acc_, we used a multivariate linear regression fit between these parameters for our PMS candidates. The comparison between our results and those obtained in other SFRs of our Galaxy and the Magellanic Clouds confirms the importance of the metallicity for the study of the dM/dt_acc_ evolution in clusters with different environmental conditions.
- ID:
- ivo://CDS.VizieR/J/A+A/624/A78
- Title:
- Masses and ages of 1059 HARPS-GTO stars
- Short Name:
- J/A+A/624/A78
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The purpose of this work is to evaluate how several elements produced by different nucleosynthesis processes behave with stellar age and provide empirical relations to derive stellar ages from chemical abundances. We derived different sets of ages using Padova and Yonsei-Yale isochrones and Hipparcos and Gaia parallaxes for a sample of more than 1000 FGK dwarf stars for which he have high-resolution R~115000 and high-quality spectra from the HARPS-GTO program. We analyzed the temporal evolution of different abundance ratios to find the best chemical clocks. We applied multivariable linear regressions to our sample of stars with a small uncertainty on age to obtain empirical relations of age as a function of stellar parameters and different chemical clocks. We find that [alpha/Fe] ratio (average of Mg, Si, and Ti), [O/Fe] and [Zn/Fe] are good age proxies with a lower dispersion than the age-metallicity dispersion. Several abundance ratios present a significant correlation with age for chemically separated thin disk stars (i.e., low-alpha) but in the case of the chemically defined thick disk stars (i.e., high-alpha) only the elements Mg, Si, Ca, and TiII show a clear correlation with age. We find that the thick disk stars are more enriched in light-s elements than thin disk stars of similar age. The maximum enrichment of s-process elements in the thin disk occurs in the youngest stars which in turn have solar metallicity. The slopes of the [X/Fe]-age relations are quite constant for O, Mg, Si, Ti, Zn, Sr, and Eu regardless of the metallicity. However, this is not the case for Al, Ca, Cu and most of the s-process elements, which display very different trends depending on the metallicity. This demonstrates the limitations of using simple linear relations based on certain abundance ratios to obtain ages for stars of different metallicities. Finally, we show that by using 3D relations with a chemical clock and two stellar parameters (either Teff, [Fe/H] or stellar mass) we can explain up to 89% of age variance in a star. A similar result is obtained when using 2D relations with a chemical clock and one stellar parameter, explaining up to a 87% of the variance. The complete understanding of how the chemical elements were produced and evolved in the Galaxy requires the knowledge of stellar ages and precise chemical abundances. We show how the temporal evolution of some chemical species change with metallicity, with remarkable variations at super-solar metallicities, which will help to better constrain the yields of different nucleosynthesis processes along the history of the Galaxy.
- ID:
- ivo://CDS.VizieR/J/ApJ/881/54
- Title:
- Masses of SNR progenitors in M83
- Short Name:
- J/ApJ/881/54
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We determine the ages of the young, resolved stellar populations at the locations of 237 optically identified supernova remnants in M83. These age distributions put constraints on the progenitor masses of the supernovae that produced 199 of the remnants. The other 38 show no evidence for having a young progenitor and are therefore good Type Ia SNR candidates. Starting from Hubble Space Telescope broadband imaging, we measured resolved stellar photometry of seven archival WFC3/UVIS fields in F336W, F438W, and F814W. We generate color-magnitude diagrams of the stars within 50pc of each SNR and fit them with stellar evolution models to obtain the population ages. From these ages we infer the progenitor mass that corresponds to the lifetime of the most prominent age within the past 50Myr. In this sample, there are 47 SNRs with best-fit progenitor masses >15M_{sun}_, and 5 of these are >15M_{sun}_ at 84% confidence. This is the largest collection of high-mass progenitors to date, including our highest-mass progenitor inference found so far, with a constraint of <8Myr. Overall, the distribution of progenitor masses has a power-law index of -3.0_-0.7_^+0.2^, steeper than Salpeter initial mass function (-2.35). It remains unclear whether the reason for the low number of high-mass progenitors is due to the difficulty of finding and measuring such objects or because only a fraction of very massive stars produce supernovae.
- ID:
- ivo://CDS.VizieR/J/MNRAS/507/300
- Title:
- Massive Compact Galaxies in MaNGA
- Short Name:
- J/MNRAS/507/300
- Date:
- 03 Dec 2021 00:51:01
- Publisher:
- CDS
- Description:
- We characterized the kinematics, morphology, and stellar population (SP) properties of a sample of massive compact quiescent galaxies (MCGs, 10<~logM*/M_{sun}_<~11 and re~1-3kpc) in the MaNGA Survey, with the goal of constraining their formation, assembly history, and assessing their relation with non-compact quiescent galaxies. We compared their properties with those of a control sample of median-sized quiescent galaxies (re~4-8kpc) with similar effective velocity dispersions. MCGs have elevated rotational support, as evidenced by a strong anticorrelation between the Gauss-Hermite moment h3 and V/{sigma}. In contrast, 30 per cent of control sample galaxies (CSGs) are slow rotators, and fast-rotating CSGs generally show a weak h3-V/{sigma} anticorrelation. MCGs and CSGs have similar ages, but MCGs are more metal-rich and {alpha}-enhanced. Both MCGs and CSGs have shallow negative metallicity gradients and flat [{alpha}/Fe] gradients. On average, MCGs and CSGs have flat age gradients, but CSGs have a significantly larger dispersion of gradient values. The kinematics and SP properties of MCGs suggest that they experienced highly dissipative gas-rich events, such as mergers, followed by an intense, short, and centrally concentrated burst of star formation, between 4 and 10Gyr ago (z~0.4-2), and had a quiet accretion history since then. This sequence of events might be analogous to, although less extreme than, the compaction events that formed compact quiescent galaxies at z~2. The small sizes of MCGs, and the high efficiency and short duration of their last star formation episode suggest that they are descendants of compact post-starburst galaxies.
- ID:
- ivo://CDS.VizieR/J/ApJ/763/101
- Title:
- Massive field OB stars in the SMC
- Short Name:
- J/ApJ/763/101
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Some theories of star formation suggest massive stars may only form in clustered environments, which would create a deficit of massive stars in low-density environments. Observationally, Massey (2002, Cat. II/236) finds such a deficit in samples of the field population in the Small and Large Magellanic Clouds, with an initial mass function (IMF) slope of {Gamma}_IMF_~4. These IMF measurements represent some of the largest known deviations from the standard Salpeter IMF slope of {Gamma}_IMF_=1.35. Here, we carry out a comprehensive investigation of the mass function above 20M_{sun}_ for the entire field population of the Small Magellanic Cloud (SMC), based on data from the Runaways and Isolated O Type Star Spectroscopic Survey of the SMC (RIOTS4). This is a spatially complete census of the entire field OB star population of the SMC obtained with the IMACS multi-object spectrograph and MIKE echelle spectrograph on the Magellan telescopes. Based on Monte Carlo simulations of the evolved present-day mass function, we find the slope of the field IMF above 20M_{sun}_ is {Gamma}_IMF_=2.3+/-0.4. We extend our IMF measurement to lower masses using BV photometry from the OGLE II survey. We use a statistical approach to generate a probability distribution for the mass of each star from the OGLE photometry, and we again find {Gamma}_IMF_=2.3+/-0.6 for stellar masses from 7M_{sun}_ to 20M_{sun}_. The discovery and removal of ten runaways in our RIOTS4 sample steepens the field IMF slope to {Gamma}_IMF_=2.8+/-0.5. We discuss the possible effects of binarity and star formation history on our results, and conclude that the steep field massive star IMF is most likely a real effect.
- ID:
- ivo://CDS.VizieR/J/ApJ/695/259
- Title:
- Massive metal-poor galaxies from SDSS
- Short Name:
- J/ApJ/695/259
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a sample of 42 high-mass low-metallicity outliers from the mass-metallicity relation of star-forming galaxies. These galaxies have stellar masses that span log(M_*_/M_{sun}_)~9.4 to 11.1 and are offset from the mass-metallicity relation by -0.3 to -0.85dex in 12+log(O/H). In general, they are extremely blue, have high star-formation rates for their masses, and are morphologically disturbed. Tidal interactions are expected to induce large-scale gas inflow to the galaxies' central regions, and we find that these galaxies' gas-phase oxygen abundances are consistent with large quantities of low-metallicity gas from large galactocentric radii diluting the central metal-rich gas. We conclude with implications for deducing gas-phase metallicities of individual galaxies based solely on their luminosities, specifically in the case of long gamma-ray burst host galaxies.
