- ID:
- ivo://CDS.VizieR/J/MNRAS/475/788
- Title:
- GAMA blue spheroids within 87 Mpc
- Short Name:
- J/MNRAS/475/788
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper, we test if nearby blue spheroid (BSph) galaxies may become the progenitors of star-forming spiral galaxies or passively evolving elliptical galaxies. Our sample comprises 428 galaxies of various morphologies in the redshift range 0.002<z<0.02 (8-87Mpc) with panchromatic data from the Galaxy and Mass Assembly survey. We find that BSph galaxies are structurally (mean effective surface brightness, effective radius) very similar to their passively evolving red counterparts. However, their star formation and other properties such as colour, age, and metallicity are more like star-forming spirals than spheroids (ellipticals and lenticulars). We show that BSph galaxies are statistically distinguishable from other spheroids as well as spirals in the multidimensional space mapped by luminosity-weighted age, metallicity, dust mass, and specific star formation rate. We use HI data to reveal that some of the BSphs are (further) developing their discs, hence their blue colours. They may eventually become spiral galaxies - if sufficient gas accretion occurs - or more likely fade into low-mass red galaxies.
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Search Results
- ID:
- ivo://lam.cesam.aspic/gama_dr3/q/ssa
- Title:
- GAMA DR3 - Simple Spectrum Access
- Short Name:
- GAMA3 SSAP
- Date:
- 20 May 2021 06:32:29
- Publisher:
- The CeSAM VO team
- Description:
- Spectra from the third data release (DR3) of GAMA.
- ID:
- ivo://CDS.VizieR/J/MNRAS/477/4116
- Title:
- GAMA. galaxy structure across green valley
- Short Name:
- J/MNRAS/477/4116
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using a sample of 472 local Universe (z<0.06) galaxies in the stellar mass range 10.25<logM*/M_{sun}_<10.75, we explore the variation in galaxy structure as a function of morphology and galaxy colour. Our sample of galaxies is sub-divided into red, green and blue colour groups and into elliptical and non-elliptical (disk-type) morphologies. Using KiDS and VIKING derived postage stamp images, a group of eight volunteers visually classified bars, rings, morphological lenses, tidal streams, shells and signs of merger activity for all systems. We find a significant surplus of rings (2.3{sigma}) and lenses (2.9{sigma}) in disk-type galaxies as they transition across the green valley. Combined, this implies a joint ring/lens green valley surplus significance of 3.3{sigma} relative to equivalent disk-types within either the blue cloud or the red sequence. We recover a bar fraction of ~44% which remains flat with colour, however, we find that the presence of a bar acts to modulate the incidence of rings and (to a lesser extent) lenses, with rings in barred disk-type galaxies more common by ~20-30 percentage points relative to their unbarred counterparts, regardless of colour. Additionally, green valley disk-type galaxies with a bar exhibit a significant 3.0{sigma} surplus of lenses relative to their blue/red analogues. The existence of such structures rules out violent transformative events as the primary end-of-life evolutionary mechanism, with a more passive scenario the favoured candidate for the majority of galaxies rapidly transitioning across the green valley.
- ID:
- ivo://CDS.VizieR/J/MNRAS/462/4336
- Title:
- GAMA. Stellar mass budget
- Short Name:
- J/MNRAS/462/4336
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We build on a recent photometric decomposition analysis of 7506 Galaxy and Mass Assembly (GAMA) survey galaxies to derive stellar mass function fits to individual spheroid and disc component populations down to a lower mass limit of log(M_*_/M_{sun}_)=8. We find that the spheroid/disc mass distributions for individual galaxy morphological types are well described by single Schechter function forms. We derive estimates of the total stellar mass densities in spheroids ({rho}_spheroid_=1.24+/-0.49x10^8^M_{sun}_Mpc^-3^h_0.7_) and discs ({rho}_disc_=1.20+/-0.45x10^8^M_{sun}_Mpc^-3^h_0.7_), which translates to approximately 50 per cent of the local stellar mass density in spheroids and 48 per cent in discs. The remaining stellar mass is found in the dwarf 'little blue spheroid' class, which is not obviously similar in structure to either classical spheroid or disc populations. We also examine the variation of component mass ratios across galaxy mass and group halo mass regimes, finding the transition from spheroid to disc mass dominance occurs near galaxy stellar mass ~10^11^M_{sun}_ and group halo mass ~10^12.5^M_{sun}_/h. We further quantify the variation in spheroid-to-total mass ratio with group halo mass for central and satellite populations as well as the radial variation of this ratio within groups.
- ID:
- ivo://CDS.VizieR/J/A+A/540/A53
- Title:
- {gamma} Cas radial velocity curve
- Short Name:
- J/A+A/540/A53
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- {gamma} Cas is the prototypical classical Be star and is recently best known for its variable hard X-ray emission. To elucidate the reasons for this emission, we mounted a multiwavelength campaign in 2010 centered around four XMM-Newton observations. The observational techniques included long baseline optical interferometry (LBOI) from two instruments at CHARA, photometry carried out by an automated photometric telescope and H{alpha} observations. Because {gamma} Cas is also known to be in a binary, we measured radial velocities from the H{alpha} line and redetermined its period as 203.55+/-0.20 days and its eccentricity as near zero.
- ID:
- ivo://CDS.VizieR/J/MNRAS/491/3586
- Title:
- 611 {gamma} Doradus stars Kepler data
- Short Name:
- J/MNRAS/491/3586
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report our survey of {gamma} Dor stars from the 4-yr Kepler mission. These stars pulsate mainly in g modes and r modes, showing period-spacing patterns in the amplitude spectra. The period-spacing patterns are sensitive to the chemical composition gradients and the near-core rotation, hence they are essential for understanding the stellar interior. We identified period-spacing patterns in 611 {gamma} Dor stars. Almost every star pulsates in dipole g modes, while about 30 per cent of stars also show clear patterns for quadrupole g modes and 16 per cent of stars present r-mode patterns. We measure periods, period spacings, and the gradient of the period spacings. These three observables guide the mode identifications and can be used to estimate the near-core rotation rate. We find many stars are hotter and show longer period-spacing patterns than theory. Using the traditional approximation of rotation (TAR), we inferred the asymptotic spacings, the near-core rotation rates, and the radial orders of the g and r modes. Most stars have a near-core rotation rate around 1d^-1^ and an asymptotic spacing around 4000s. We also find that many stars rotate more slowly than predicted by theory for unclear reasons. 11 stars show rotational splittings with fast rotation rates. We compared the observed slope-rotation relation with the theory and find a large spread. We detected rotational modulations in 58 stars and used them to derive the core-to-surface rotation ratios. The interiors rotate faster than the cores in most stars, but by no more than 5 per cent.
- ID:
- ivo://CDS.VizieR/J/A+A/556/A52
- Title:
- {gamma} Dor stars from Kepler
- Short Name:
- J/A+A/556/A52
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The launches of the MOST, CoRoT, and Kepler missions opened up a new era in asteroseismology, the study of stellar interiors via interpretation of pulsation patterns observed at the surfaces of large groups of stars. These space missions deliver a huge amount of high-quality photometric data suitable to study numerous pulsating stars. Our ultimate goal is a detection and analysis of an extended sample of {gamma} Dor-type pulsating stars with the aim to search for observational evidence of non-uniform period spacings and rotational splittings of gravity modes in main-sequence stars typically twice as massive as the Sun. This kind of diagnostic can be used to deduce the internal rotation law and to estimate the amount of rotational mixing in the near core regions. We applied an automated supervised photometric classification method to select a sample of 69 Gamma Doradus ({gamma} Dor) candidate stars. We used an advanced method to extract the Kepler light curves from the pixel data information using custom masks. For 36 of the stars, we obtained high-resolution spectroscopy with the HERMES spectrograph installed at the Mercator telescope. The spectroscopic data are analysed to determine the fundamental parameters like Teff, log g, vsini, and [M/H]. We find that all stars for which spectroscopic estimates of Teff and log g are available fall into the region of the HR diagram, where the {gamma} Dor and {delta} Sct instability strips overlap. The stars cluster in a 700 K window in effective temperature; log g measurements suggest luminosity class IV-V, i.e. sub-giant or main-sequence stars. From the Kepler photometry, we identify 45 {gamma} Dor-type pulsators, 14 {gamma} Dor/{delta} Sct hybrids, and 10 stars, which are classified as "possibly {gamma} Dor/{delta} Sct hybrid pulsators". We find a clear correlation between the spectroscopically derived vsini and the frequencies of independent pulsation modes.
- ID:
- ivo://CDS.VizieR/J/MNRAS/458/2307
- Title:
- gamma Dor stars spectroscopic survey
- Short Name:
- J/MNRAS/458/2307
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a spectroscopic survey of known and candidate {gamma} Doradus stars. The high-resolution, high signal-to-noise spectra of 52 objects were collected by five different spectrographs. The spectral classification, atmospheric parameters (T_eff_, logg, {xi}), vsini and chemical composition of the stars were derived. The stellar spectral and luminosity classes were found between G0-A7 and IV-V, respectively. The initial values for T_eff_ and logg were determined from the photometric indices and spectral energy distribution. Those parameters were improved by the analysis of hydrogen lines. The final values of T_eff_, logg and {xi} were derived from the iron lines analysis. The T_eff_ values were found between 6000K and 7900K, while log g values range from 3.8 to 4.5dex. Chemical abundances and vsin i values were derived by the spectrum synthesis method. The vsini values were found between 5 and 240km/s. The chemical abundance pattern of {gamma} Doradus stars were compared with the pattern of non-pulsating stars. It turned out that there is no significant difference in abundance patterns between these two groups. Additionally, the relations between the atmospheric parameters and the pulsation quantities were checked. A strong correlation between the vsini and the pulsation periods of {gamma} Doradus variables was obtained. The accurate positions of the analysed stars in the Hertzsprung-Russell diagram have been shown. Most of our objects are located inside or close to the blue edge of the theoretical instability strip of {gamma} Doradus.
- ID:
- ivo://CDS.VizieR/J/MNRAS/428/220
- Title:
- Gamma-ray AGN type determination
- Short Name:
- J/MNRAS/428/220
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Fermi Gamma-ray Space Telescope (Fermi) is producing the most detailed inventory of the gamma-ray sky to date. Despite tremendous achievements approximately 25 per cent of all Fermi extragalactic sources in the Second Fermi Large Area Telescope Catalogue (2FGL) are listed as active galactic nuclei (AGN) of uncertain type. Typically, these are suspected blazar candidates without a conclusive optical spectrum or lacking spectroscopic observations. Here, we explore the use of machine-learning algorithms - random forests and support vector machines - to predict specific AGN subclass based on observed gamma-ray spectral properties. After training and testing on identified/associated AGN from the 2FGL we find that 235 out of 269 AGN of uncertain type have properties compatible with gamma-ray BL Lacertae and flat-spectrum radio quasars with accuracy rates of 85 per cent. Additionally, direct comparison of our results with class predictions made after following the infrared colour-colour space of Massaro et al. shows that the agreement rate is over four-fifths for 54 overlapping sources, providing independent cross-validation. These results can help tailor follow-up spectroscopic programmes and inform future pointed surveys with ground-based Cherenkov telescopes.
- ID:
- ivo://CDS.VizieR/J/ApJ/626/95
- Title:
- Gamma-ray blazar candidates
- Short Name:
- J/ApJ/626/95
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In preparation for the Gamma-Ray Large Area Space Telescope (GLAST), we have compiled a sample of blazar candidates to increase the pool of well-studied active galactic nuclei from which GLAST counterparts will be drawn.