- ID:
- ivo://CDS.VizieR/J/A+A/558/A82
- Title:
- V4332 Sgr optical spectropolarimetry
- Short Name:
- J/A+A/558/A82
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The eruption of V4332 Sgr was observed in 1994 and was classified as belonging to red transients of the V838 Mon type. Optical spectroscopy obtained a few years after the eruption showed a faint M-type stellar spectrum underlying numerous molecular and atomic emission features. We suggested that the central object in V4332 Sgr is now hidden in a dusty disc and that the photospheric spectrum of this object observed in the optical results from scattering of the radiation of the central star on dust grains in the circumstellar matter. The optical continuum of the object, as resulting from scattering on dust grains, is expected to be polarized. The emission features on the contrary - as observed directly from circumstellar regions, are expected to be unpolarized. We present and analyse spectropolarimetric observations of V4332 Sgr in the optical region. The continuum is linearly polarized with a typical degree of 16.6%. A clear depolarization is observed in the spectral regions where emission features contribute significantly to the observed flux. The only prominent exception is the CaI emission line at 6573{AA}, which is polarized in 21%. The results of our spectropolarimetric observations are in accord with the proposed geometry of the system and the advocated nature of the observed optical spectrum of V4332 Sgr - the continuum is not seen directly but due to scattering on dust within the disk and polar outflow, while most of the gas emission comes from the polar outflow excited by the radiation field of the central source. Additionally, the observed polarization patterns suggest a stratification of the outflow.
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- ID:
- ivo://CDS.VizieR/J/A+A/568/L8
- Title:
- VUDS extreme emission line 0.2<~z<~0.9 galaxies
- Short Name:
- J/A+A/568/L8
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery of 31 low-luminosity (-14.5>~M_AB_(B)>~-18.8), extreme emission line galaxies (EELGs) at 0.2<~z<~0.9 identified by their unusually high rest-frame equivalent widths (100<=EW[OIII]<=1700{AA}) as part of the VIMOS Ultra Deep Survey (VUDS). VIMOS optical spectra of unprecedented sensitivity (I_AB_~25mag) along with multiwavelength photometry and HST imaging are used to investigate spectrophotometric properties of this unique sample and to explore, for the first time, the very low stellar mass end (M_*_<~10^8^M_{sun}_) of the luminosity-metallicity (LZR) and mass-metallicity (MZR) relations at z<1. Characterized by their extreme compactness (R_50_<1kpc), low stellar mass and enhanced specific star formation rates (sSFR=SFR/M_*_~10^-9^-10^-7^yr^-1^), the VUDS EELGs are blue dwarf galaxies likely experiencing the first stages of a vigorous galaxy-wide starburst. Using Te-sensitive direct and strong-line methods, we find that VUDS EELGs are low-metallicity (7.5<~12+log(O/H)<~8.3) galaxies with high ionization conditions (log(q_ion_)>~8cm/s), including at least three EELGs showing HeII{lambda}4686{AA} emission and four extremely metal-poor (<~10% solar) galaxies. The LZR and MZR followed by VUDS EELGs show relatively large scatter, being broadly consistent with the extrapolation toward low luminosity and mass from previous studies at similar redshift. However, we find evidence that galaxies with younger and more vigorous star formation --as characterized by their larger EWs, ionization and sSFR-- tend to be more metal poor at a given stellar mass.
- ID:
- ivo://CDS.VizieR/J/A+A/609/A34
- Title:
- VUV absorption cross section of CO_2_
- Short Name:
- J/A+A/609/A34
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We quantify the temperature dependency of the VUV absorption cross section of carbon dioxide. The VUV absorption cross section of CO_2_ increases with the temperature. The absorption we measured at 150K seems to be close to the absorption of CO_2_ in the fundamental ground state. The absorption cross section can be separated in two parts: a continuum and a fine structure superimposed on the continuum. The variation of the continuum of absorption can be represented by the sum of three gaussian functions. We used these data in our 1D thermo-photochemical model in order to study their impact on the predicted atmospheric composition of warm exoplanets. Using data at high temperature in thermo-photochemical models modifies significantly the abundance and the photodissociation rates of many species, in addition to carbon dioxide, such as methane and ammonia. These deviations have an impact on synthetic transmission spectra, leading to variations of up to 5ppm.
- ID:
- ivo://CDS.VizieR/J/MNRAS/437/532
- Title:
- VY CMa molecular line spectra
- Short Name:
- J/MNRAS/437/532
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an analysis of the far-infrared and submillimetre molecular emission-line spectrum of the luminous M-supergiant VY CMa, observed with the Spectral and Photometric Imaging Receiver (SPIRE) and Photodetector Array Camera and Spectrometer for Herschel spectrometers aboard the Herschel Space Observatory. Over 260 emission lines were detected in the 190-650{mu}m SPIRE Fourier Transform Spectrometer spectra, with one-third of the observed lines being attributable to H_2_O. Other detected species include CO, ^13^CO, H_2_O, SiO, HCN, SO, SO2, CS, H_2_S and NH_3_. Our model fits to the observed ^12^CO and ^13^CO line intensities yield a ^12^C/^13^C ratio of 5.6+/-1.8, consistent with measurements of this ratio for other M-supergiants, but significantly lower than previously estimated for VY CMa from observations of lower-J lines. The spectral line energy distribution for 20 SiO rotational lines shows two temperature components: a hot component at ~1000K, which we attribute to the stellar atmosphere and inner wind, plus a cooler ~200K component, which we attribute to an origin in the outer circumstellar envelope. We fit the line fluxes of ^12^CO, ^13^CO, H_2_O and SiO, using the smmol non-local thermodynamic equilibrium (LTE) line transfer code, with a mass-loss rate of 1.85x10^-4^M_{sun}_/yr between 9R* and 350R*. We also fit the observed line fluxes of ^12^CO, ^13^CO, H_2_O and SiO with smmol non-LTE line radiative transfer code, along with a mass-loss rate of 1.85x10^-4^M_{sun}_/yr. To fit the high rotational lines of CO and H_2_O, the model required a rather flat temperature distribution inside the dust condensation radius, attributed to the high H_2_O opacity. Beyond the dust condensation radius the gas temperature is fitted best by an r-0.5 radial dependence, consistent with the coolant lines becoming optically thin. Our H_2_O emission-line fits are consistent with an ortho:para ratio of 3 in the outflow.
- ID:
- ivo://CDS.VizieR/J/A+A/617/A16
- Title:
- VY Scl reduced spectra & radial velocities
- Short Name:
- J/A+A/617/A16
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In the context of a large campaign to determine the system parameters of high mass transfer cataclysmic variables, we found VY Scl in a low state in 2008. Making use of this low state, we study the stellar components of the binary with little influence of the normally dominating accretion disc. Time-resolved spectroscopy and photometry of VY Scl taken during the low state are presented. We analysed the light-curve and radial velocity curve and use time-resolved spectroscopy to calculate Doppler maps of the dominant emission lines. The spectra show narrow emission lines of Halpha, Hbeta, HeI, NaI D, and FeII, as well as faint TiO absorption bands that trace the motion of the irradiated secondary star, and Halpha and HeI emission line wings that trace the motion of the white dwarf. From these radial velocities, we find an orbital period of 3.84h, and put constraints on binary parameters such as the mass ratio M2/M1 of 0.43 and the inclination of 15. With a secondary mass between 0.3 and 0.35M_{sun}_, we derive the mass for the white dwarf as M1=0.6-1.1M_{sun}_.
- ID:
- ivo://CDS.VizieR/J/A+A/577/A127
- Title:
- W49A JCMT Spectral Legacy Survey spectroscopy
- Short Name:
- J/A+A/577/A127
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The massive and luminous star-forming region W49A is a well-known Galactic candidate to probe the physical conditions and chemistry similar to those expected in external starburst galaxies. We aim to probe the physical and chemical structure of W49A on a spatial scale of ~0.8pc based on the JCMT Spectral Legacy Survey, which covers the frequency range between 330 and 373GHz. The wide 2x2-arcmin field and the high spectral resolution of the HARP instrument on JCMT provides information on the spatial structure and kinematics of the cloud traced by the observed molecular lines. For species where multiple transitions are available, we estimate excitation temperatures and column densities using a population diagram method that takes beam dilution and optical depth corrections into account. We detected 255 transitions corresponding to 63 species in the 330-373GHz range at the center position of W49A. Excitation conditions can be probed for 14 molecules, including the complex organic molecules CH_3_CCH, CH_3_CN, and CH_3_OH. The chemical composition suggests the importance of shock, photon-dominated region (PDR), and hot core chemistry. Many molecular lines show a significant spatial extent across the maps including CO and its isotopologues, high density tracers (e.g., HCN, HNC, CS, HCO^+^), and tracers of UV irradiation (e.g., CN and C_2_H). The spatially extended species reveal a complex velocity-structure of W49A with possible infall and outflow motions. Large variations are seen between the subregions with mostly blue-shifted emission toward the eastern tail, mostly red-shifted emission toward the northern clump, and emission peaking around the expected source velocity toward the southwest clump. A comparison of column density ratios of characteristic species observed toward W49A to Galactic PDRs suggests that while the chemistry toward the W49A center is driven by a combination of UV irradiation and shocks, UV irradiation dominates for the northern clump, eastern tail, and southwest clump regions. A comparison to a starburst galaxy and an active galactic nucleus suggests similar C_2_H, CN, and H_2_CO abundances (with respect to the dense gas tracer ^34^CS) between the ~0.8pc scale probed for W49A and the >1kpc regions in external galaxies with global star formation.
3027. Warm IRAS sources. II.
- ID:
- ivo://CDS.VizieR/J/A+AS/96/389
- Title:
- Warm IRAS sources. II.
- Short Name:
- J/A+AS/96/389
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present optical spectra for a sample of 563 high-latitude IRAS sources selected from the Point Source Catalog to have relatively warm 25 to 60 micron colours. We have shown this selection criterion to be an efficient indicator for finding Seyfert galaxies. Plots of the optical spectra are shown and the fluxes of the strongest emission lines in these spectra are tabulated. After excluding 128 sources which are clearly galactic foreground objects, we obtained spectroscopic information for 358 extragalactic objects. Emission-line ratios have been used to classify these objects, resulting in 80 Seyfert 1, 141 Seyfert 2 and 133 HII-type objects. In comparison with samples of active nuclei selected in other ways, about 50% of known Seyfert nuclei are included by our colour criteria. This fraction is larger for high luminosities, reaching 80% for quasar luminosities. For lower-luminosity objects, contamination by the host galaxies becomes important and the sample becomes seriously incomplete. It should be moderately complete and representative for core luminosities greater than 10^23.5^W/Hz at 12m. Finally, the infrared luminosity function for each type of object is derived; the shapes for Seyfert 1 and 2 nuclei are identical, with a type 2/type 1 space-density ratio of 3.0. Our census is consistent with an obscuration scheme for producing both types of object from a single parent population, though the origin of excess cool IR radiation Irom many Seyferts is still unclear. We note the appearance of an apparent type II supernova in IRAS 0225-103 observed in 1985 September. Its spectrum suggests that it was observed between 1 and 2 months after maximum, perhaps in a "plateau" phase.
- ID:
- ivo://CDS.VizieR/J/AJ/156/295
- Title:
- Warm molecular hydrogen in nearby LIRGs
- Short Name:
- J/AJ/156/295
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Mid-infrared molecular hydrogen (H_2_) emission is a powerful cooling agent in galaxy mergers and in radio galaxies; it is a potential key tracer of gas evolution and energy dissipation associated with mergers, star formation, and accretion onto supermassive black holes. We detect mid-IR H_2_ line emission in at least one rotational transition in 91% of the 214 Luminous Infrared Galaxies (LIRGs) observed with Spitzer as part of the Great Observatories All-sky LIRG Survey. We use H_2_ excitation diagrams to estimate the range of masses and temperatures of warm molecular gas in these galaxies. We find that LIRGs in which the IR emission originates mostly from the Active Galactic Nuclei (AGN) have about 100 K higher H_2_ mass-averaged excitation temperatures than LIRGs in which the IR emission originates mostly from star formation. Between 10% and 15% of LIRGs have H_2_ emission lines that are sufficiently broad to be resolved or partially resolved by the high-resolution modules of Spitzer's Infrared Spectrograph (IRS). Those sources tend to be mergers and contain AGN. This suggests that a significant fraction of the H_2_ line emission is powered by AGN activity through X-rays, cosmic rays, and turbulence. We find a statistically significant correlation between the kinetic energy in the H_2_ gas and the H_2_ to IR luminosity ratio. The sources with the largest warm gas kinetic energies are mergers. We speculate that mergers increase the production of bulk inflows leading to observable broad H_2_ profiles and possibly denser gas.
- ID:
- ivo://CDS.VizieR/J/ApJ/669/959
- Title:
- Warm molecular hydrogen in SINGS galaxy sample
- Short Name:
- J/ApJ/669/959
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Results on the properties of warm molecular hydrogen in 57 normal galaxies are derived from measurements of H_2_ rotational transitions, obtained as part of SINGS. This study extends previous extragalactic surveys of emission lines of H_2_ to fainter and more common systems (LFIR = 10^7^-6x10^10^L_{sun}_). The 17um S(1) transition is securely detected in the nuclear regions of 86% of galaxies with stellar masses above 10^9.5^M_{sun}_.
- ID:
- ivo://CDS.VizieR/J/MNRAS/439/2701
- Title:
- Warm molecular hydrogen in ULIRGs
- Short Name:
- J/MNRAS/439/2701
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Ultraluminous infrared galaxies (ULIRGs) show on average three times more emission in the rotational transitions of molecular hydrogen than expected based on their star formation rates. Using Spitzer archival data, we investigate the origin of excess warm H_2_ emission in 115 ULIRGs of the IRAS 1Jy sample. We find a strong correlation between H_2_ and [FeII] line luminosities, suggesting that excess H_2_ is produced in shocks propagating within neutral or partially ionized medium. This view is supported by the correlations between H_2_ and optical line ratios diagnostic of such shocks. The galaxies powered by star formation and those powered by active nuclei follow the same relationship between H_2_ and [FeII], with emission line width being the major difference between these classes (~500 and ~1000km/s, respectively). We conclude that excess H_2_ emission is produced as the supernovae and active nuclei drive outflows into the neutral interstellar medium of the ULIRGs. A weak positive correlation between H_2_ and the length of the tidal tails indicates that these outflows are more likely to be encountered in more advanced mergers, but there is no evidence for excess H_2_ produced as a result of the collision shocks during the final coalescence.
