scholarly journals The Hα line emission of the Be star β Psc: the last 40 yr

2020 ◽  
Vol 501 (1) ◽  
pp. 747-755
Author(s):  
Ronaldo S Levenhagen ◽  
Marcos P Diaz ◽  
Eduardo B Amôres ◽  
Nelson V Leister
Keyword(s):  
Additional Data ◽  
State Of The Art ◽  
Spectral Energy Distribution ◽  
Line Emission ◽  
Spectral Energy ◽  
Line Profiles ◽  
Gas Density ◽  
Geometric Deformation ◽  
Be Star ◽  
Effects Of Rotation

ABSTRACT A study on the photosphere and disc of the Be star β Psc is presented. We recover almost 40 yr of high-resolution spectroscopic observations and additional data gathered from the BeSS data base. We evaluate the photospheric parameters from the spectral energy distribution (SED) and fittings of state-of-the-art non-LTE model atmospheres to observed helium, carbon, silicon, and magnesium line profiles. Our models include the stellar geometric deformation as well as the co-latitude dependence of temperature and gravity, aiming to derive the effects of rotation on the stellar parameters. We estimate the circumstellar disc parameters from the fitting of models assuming different disc properties, namely its radius and gas density profile. The disc inclination angle i is constrained from the fittings of He i 4471 Å, Mg ii 4481 Å, C ii 4267 Å,  and Si ii 4128, 4132 Å  lines with gravity darkened models. Our findings, based on model fittings, suggest that during the last 40 yr, the disc radius changed within the interval 5.5 ≤ Rd ≤ 7.8 $R/R_{*}\,$, the disc base gas density within 5 × 10−13 ≤ ρ ≤ 1 × 10−12 g cm−3, while the radial power-law density index m assumed values between 2.0 and 2.3. These results are in agreement with recent works dealing with spectroscopic and interferometric measurements of this object.

scholarly journals An ALMA survey of the brightest sub-millimetre sources in the SCUBA-2–COSMOS field

2020 ◽  
Vol 495 (3) ◽  
pp. 3409-3430 ◽  
Author(s):  
J M Simpson ◽  
Ian Smail ◽  
U Dudzevičiūtė ◽  
Y Matsuda ◽  
B-C Hsieh ◽  
...  
Keyword(s):  
Pilot Study ◽  
Flux Density ◽  
Luminosity Function ◽  
Spectral Energy Distribution ◽  
Line Emission ◽  
Spectral Energy ◽  
Complete Sample ◽  
Photometric Redshifts ◽  
Photometric Redshift ◽  
Number Counts

ABSTRACT We present an ALMA study of the ∼180 brightest sources in the SCUBA-2 850-μm map of the COSMOS field from the S2COSMOS survey, as a pilot study for AS2COSMOS – a full survey of the ∼1000 sources in this field. In this pilot study, we have obtained 870-μm continuum maps of an essentially complete sample of the brightest 182 sub-millimetre sources ($S_{850\, \mu \rm m}\gt $ 6.2 mJy) in COSMOS. Our ALMA maps detect 260 sub-millimetre galaxies (SMGs) spanning a range in flux density of $S_{870\, \mu \rm m}$ = 0.7–19.2 mJy. We detect more than one SMG counterpart in 34 ± 2 per cent of sub-millimetre sources, increasing to 53 ± 8 per cent for SCUBA-2 sources brighter than $S_{850\, \mu \rm m}\gt $ 12 mJy. We estimate that approximately one-third of these SMG–SMG pairs are physically associated (with a higher rate for the brighter secondary SMGs, $S_{870\, \mu \rm m}\gtrsim$ 3 mJy), and illustrate this with the serendipitous detection of bright [C ii] 157.74-μm line emission in two SMGs, AS2COS 0001.1 and 0001.2 at z = 4.63, associated with the highest significance single-dish source. Using our source catalogue, we construct the interferometric 870-μm number counts at $S_{870\, \mu \rm m}\gt $ 6.2 mJy. We use the extensive archival data of this field to construct the multiwavelength spectral energy distribution of each AS2COSMOS SMG, and subsequently model this emission with magphys to estimate their photometric redshifts. We find a median photometric redshift for the $S_{870\, \mu \rm m}\gt $ 6.2 mJy AS2COSMOS sample of z = 2.87 ± 0.08, and clear evidence for an increase in the median redshift with 870-μm flux density suggesting strong evolution in the bright end of the 870-μm luminosity function.

scholarly journals Properties of LBGs with [OIII] detection at z ∼ 3.5

2019 ◽  
Vol 631 ◽  
pp. A123 ◽  
Author(s):  
Fang-Ting Yuan ◽  
Denis Burgarella ◽  
David Corre ◽  
Veronique Buat ◽  
Médéric Boquien ◽  
...  
Keyword(s):  
Physical Properties ◽  
Emission Line ◽  
Near Infrared ◽  
Spectral Energy Distribution ◽  
Formation Rate ◽  
Line Emission ◽  
Stellar Mass ◽  
Spectral Energy ◽  
Emission Data ◽  
The Impact

Context. Nebular emission lines are critical to measure physical properties in the ionized gas (e.g., metallicity, the star formation rate, or dust attenuation). They also account for a significant fraction of broadband fluxes, in particular at the highest redshifts, and therefore can strongly affect the determination of other physical properties, such as the stellar mass, which are crucial in shaping our understanding of galaxy formation and evolution. Aims. We investigate a sample of 51 Lyman break galaxies at 3.0 <  zspec <  3.8 with detected [OIII] line emissions and estimated the physical properties of these galaxies to examine the impact of including nebular emission data in the Spectral energy distribution (SED) fitting. Methods. We used the Code Investigating GALaxy Emission (CIGALE) to fit the rest-frame ultraviolet-to-near-infrared SEDs of these galaxies and their emission line data simultaneously. We ran CIGALE with and without the nebular model or the emission line data, and compare the results to show the importance of including the nebular emission line data in the SED fitting. Results. We find that without the nebular model, the SED fitting overestimates the stellar mass due to the strong [OIII] lines that are redshifted to the Ks-band, which is consistent with previous results. The emission line data are necessary to constrain the nebular model in the SED fitting. We examine the Ks-band excess, which is mostly used to estimate the emissions of the [OIII]+Hβ lines when there is no spectral data, and we find that the estimation and observation are statistically consistent. However, the difference can reach up to more than 1 dex in some catastrophic cases, which shows the importance of obtaining spectroscopic measurements for these lines. We also estimate the equivalent width of the Hβ absorption and find it negligible compared to the Hβ emission. Conclusions. Line emission is important to constrain the nebular models and to obtain reliable estimates of the physical properties of galaxies. These data should be taken into account in the SED fitting.

scholarly journals The circumstellar environment of the FS CMa star IRAS 00470+6429

2010 ◽  
Vol 6 (S272) ◽  
pp. 384-385
Author(s):  
Alex C. Carciofi ◽  
Anatoly S. Miroshnichenko ◽  
Jon E. Bjorkman
Keyword(s):  
Main Sequence ◽  
Spectral Energy Distribution ◽  
Spectral Energy ◽  
Line Profiles ◽  
Polar Wind ◽  
Strong Emission ◽  
Novel Approach ◽  
Consistent Solution ◽  
Dust Destruction ◽  
Circumstellar Environment

AbstractFS CMa type stars are a recently described group of objects with the B[e] phenomenon that exhibit strong emission-line spectra and strong IR excesses. In this paper we report the first attempt for a detailed modeling of IRAS 00470+6429, for which we have the best set of observations. Our modeling is based on two key assumptions: the star has a main-sequence luminosity for its spectral type (B2) and that the circumstellar (CS) envelope is bimodal, composed of a slowly outflowing disk-like wind and a fast polar wind. Both outflows are assumed to be purely radial. We adopt a novel approach to describe the dust formation site in the wind that employs timescale arguments for grain condensation and a self-consistent solution for the dust destruction surface. With the above assumptions we were able to reproduce satisfactorily many observational properties of IRAS 00470+6429, including the HI line profiles and the overall shape of the spectral energy distribution.

scholarly journals Visible and near-infrared spectro-interferometric analysis of the edge-on Be star o Aquarii

2020 ◽  
Vol 636 ◽  
pp. A110 ◽  
Author(s):  
E. S. G. de Almeida ◽  
A. Meilland ◽  
A. Domiciano de Souza ◽  
P. Stee ◽  
D. Mourard ◽  
...  
Keyword(s):  
Steady State ◽  
Near Infrared ◽  
Spectral Energy Distribution ◽  
Kinematic Model ◽  
Spectral Energy ◽  
Circumstellar Disk ◽  
Be Stars ◽  
Rotational Rate ◽  
Disk Structure ◽  
Be Star

Aims. We present a detailed visible and near-infrared spectro-interferometric analysis of the Be-shell star o Aquarii from quasi-contemporaneous CHARA/VEGA and VLTI/AMBER observations. Methods. We analyzed spectro-interferometric data in the Hα (VEGA) and Brγ (AMBER) lines using models of increasing complexity: simple geometric models, kinematic models, and radiative transfer models computed with the 3D non-LTE code HDUST. Results. We measured the stellar radius of o Aquarii in the visible with a precision of 8%: 4.0 ± 0.3 R⊙. We constrained the circumstellar disk geometry and kinematics using a kinematic model and a MCMC fitting procedure. The emitting disk sizes in the Hα and Brγ lines were found to be similar, at ~10–12 stellar diameters, which is uncommon since most results for Be stars indicate a larger extension in Hα than in Brγ. We found that the inclination angle i derived from Hα is significantly lower (~15°) than the one derived from Brγ: i ~ 61.2° and 75.9°, respectively. While the two lines originate from a similar region of the disk, the disk kinematics were found to be near to the Keplerian rotation (i.e., β = −0.5) in Brγ (β ~ −0.43), but not in Hα (β ~ −0.30). After analyzing all our data using a grid of HDUST models (BeAtlas), we found a common physical description for the circumstellar disk in both lines: a base disk surface density Σ0 = 0.12 g cm−2 and a radial density law exponent m = 3.0. The same kind of discrepancy, as with the kinematic model, is found in the determination of i using the BeAtlas grid. The stellar rotational rate was found to be very close (~96%) to the critical value. Despite being derived purely from the fit to interferometric data, our best-fit HDUST model provides a very reasonable match to non-interferometric observables of o Aquarii: the observed spectral energy distribution, Hα and Brγ line profiles, and polarimetric quantities. Finally, our analysis of multi-epoch Hα profiles and imaging polarimetry indicates that the disk structure has been (globally) stable for at least 20 yr. Conclusions. Looking at the visible continuum and Brγ emission line only, o Aquarii fits in the global scheme of Be stars and their circumstellar disk: a (nearly) Keplerian rotating disk well described by the viscous decretion disk (VDD) model. However, the data in the Hα line shows a substantially different picture that cannot fully be understood using the current generation of physical models of Be star disks. The Be star o Aquarii presents a stable disk (close to the steady-state), but, as in previous analyses, the measured m is lower than the standard value in the VDD model for the steady-state regime (m = 3.5). This suggests that some assumptions of this model should be reconsidered. Also, such long-term disk stability could be understood in terms of the high rotational rate that we measured for this star, the rate being a main source for the mass injection in the disk. Our results on the stellar rotation and disk stability are consistent with results in the literature showing that late-type Be stars are more likely to be fast rotators and have stable disks.

scholarly journals The ‘Red Radio Ring’: ionized and molecular gas in a starburst/active galactic nucleus at z ∼ 2.55

2019 ◽  
Vol 488 (2) ◽  
pp. 1489-1500 ◽  
Author(s):  
Kevin C Harrington ◽  
A Vishwas ◽  
A Weiß ◽  
B Magnelli ◽  
L Grassitelli ◽  
...  
Keyword(s):  
Fine Structure ◽  
Spectral Energy Distribution ◽  
Formation Rate ◽  
Line Emission ◽  
Far Infrared ◽  
Spectral Energy ◽  
Molecular Gas ◽  
H Ii Regions ◽  
Galaxy Assembly ◽  
Dust Attenuation

ABSTRACT We report the detection of the far-infrared (FIR) fine-structure line of singly ionized nitrogen, [N ii] 205 $\mu$m , within the peak epoch of galaxy assembly, from a strongly lensed galaxy, hereafter ‘The Red Radio Ring’; the RRR, at z = 2.55. We combine new observations of the ground-state and mid-J transitions of CO (Jup = 1, 5, 8), and the FIR spectral energy distribution (SED), to explore the multiphase interstellar medium (ISM) properties of the RRR. All line profiles suggest that the H ii regions, traced by [N ii] 205 $\mu$m , and the (diffuse and dense) molecular gas, traced by CO, are cospatial when averaged over kpc-sized regions. Using its mid-IR-to-millimetre (mm) SED, we derive a non-negligible dust attenuation of the [N ii] 205 $\mu$m line emission. Assuming a uniform dust screen approximation results a mean molecular gas column density &gt;1024 cm−2, with a molecular gas-to-dust mass ratio of 100. It is clear that dust attenuation corrections should be accounted for when studying FIR fine-structure lines in such systems. The attenuation corrected ratio of $L_{\rm N\,{\small II}205} / L_{\rm IR(8\!-\!1000\, \mu m)} = 2.7 \times 10^{-4}$ is consistent with the dispersion of local and z &gt; 4 SFGs. We find that the lower limit, [N ii] 205 $\mu$m -based star formation rate (SFR) is less than the IR-derived SFR by a factor of 4. Finally, the dust SED, CO line SED, and $L_{\rm N\,{\small II}205}$ line-to-IR luminosity ratio of the RRR is consistent with a starburst-powered ISM.

scholarly journals Single magnetic white dwarfs with Balmer emission lines: a small class with consistent physical characteristics as possible signposts for close-in planetary companions

2020 ◽  
Vol 499 (2) ◽  
pp. 2564-2574
Author(s):  
Boris T Gänsicke ◽  
Pablo Rodríguez-Gil ◽  
Nicola P Gentile Fusillo ◽  
Keith Inight ◽  
Matthias R Schreiber ◽  
...  
Keyword(s):  
White Dwarf ◽  
White Dwarfs ◽  
Late Onset ◽  
Spectral Energy Distribution ◽  
Giant Planet ◽  
Line Emission ◽  
Emission Lines ◽  
Spectral Energy ◽  
Common Mechanism ◽  
Small Class

ABSTRACT We report the identification of SDSS J121929.45+471522.8 as the third apparently isolated magnetic (B ≃ 18.5 ± 1.0 MG) white dwarf exhibiting Zeeman-split Balmer emission lines. The star shows coherent variability at optical wavelengths with an amplitude of ≃0.03 mag and a period of 15.26 h, which we interpret as the spin period of the white dwarf. Modelling the spectral energy distribution and Gaia parallax, we derive a white dwarf temperature of 7500 ± 148 K, a mass of 0.649 ± 0.022 M⊙, and a cooling age of 1.5 ± 0.1 Gyr, as well as an upper limit on the temperature of a sub-stellar or giant planet companion of ≃250 K. The physical properties of this white dwarf match very closely those of the other two magnetic white dwarfs showing Balmer emission lines: GD356 and SDSS J125230.93−023417.7. We argue that, considering the growing evidence for planets and planetesimals on close orbits around white dwarfs, the unipolar inductor model provides a plausible scenario to explain the characteristics of this small class of stars. The tight clustering of the three stars in cooling age suggests a common mechanism switching the unipolar inductor on and off. Whereas Lorentz drift naturally limits the lifetime of the inductor phase, the relatively late onset of the line emission along the white dwarf cooling sequence remains unexplained.

scholarly journals DZ Chamaeleontis: a bona fide photoevaporating disc

2018 ◽  
Vol 610 ◽  
pp. A13 ◽  
Author(s):  
H. Canovas ◽  
B. Montesinos ◽  
M. R. Schreiber ◽  
L. A. Cieza ◽  
C. Eiroa ◽  
...  
Keyword(s):  
Accretion Rate ◽  
Spectral Energy Distribution ◽  
Line Emission ◽  
Spectral Energy ◽  
T Tauri ◽  
Stellar Radiation ◽  
Infrared Spectral ◽  
Chromospheric Emission ◽  
Imaging Polarimetry ◽  
Bona Fide

Context. DZ Cha is a weak-lined T Tauri star (WTTS) surrounded by a bright protoplanetary disc with evidence of inner disc clearing. Its narrow Hα line and infrared spectral energy distribution suggest that DZ Cha may be a photoevaporating disc. Aims. We aim to analyse the DZ Cha star + disc system to identify the mechanism driving the evolution of this object. Methods. We have analysed three epochs of high resolution optical spectroscopy, photometry from the UV up to the sub-mm regime, infrared spectroscopy, and J-band imaging polarimetry observations of DZ Cha. Results. Combining our analysis with previous studies we find no signatures of accretion in the Hα line profile in nine epochs covering a time baseline of ~20 yr. The optical spectra are dominated by chromospheric emission lines, but they also show emission from the forbidden lines [SII] 4068 and [OI] 6300Å that indicate a disc outflow. The polarized images reveal a dust depleted cavity of ~7 au in radius and two spiral-like features, and we derive a disc dust mass limit of Mdust< 3 MEarth from the sub-mm photometry. No stellar (M⋆> 80 MJup) companions are detected down to 0.̋07 (~8 au, projected). Conclusions. The negligible accretion rate, small cavity, and forbidden line emission strongly suggests that DZ Cha is currently at the initial stages of disc clearing by photoevaporation. At this point the inner disc has drained and the inner wall of the truncated outer disc is directly exposed to the stellar radiation. We argue that other mechanisms like planet formation or binarity cannot explain the observed properties of DZ Cha. The scarcity of objects like this one is in line with the dispersal timescale (≲105 yr) predicted by this theory. DZ Cha is therefore an ideal target to study the initial stages of photoevaporation.

scholarly journals Spitzer observations of planetary nebulae

2011 ◽  
Vol 7 (S283) ◽  
pp. 21-28
Author(s):  
You-Hua Chu
Keyword(s):  
Energy Distribution ◽  
Galactic Plane ◽  
Spectral Energy Distribution ◽  
Line Emission ◽  
Circumstellar Dust ◽  
Spectral Energy ◽  
Targeted Imaging ◽  
Molecular Line ◽  
Dust Disks ◽  
Central Stars

AbstractThe Spitzer Space Telescope has three science instruments (IRAC, MIPS, and IRS) that can take images at 3.6, 4.5, 5.8, 8.0, 24, 70, and 160 μm, spectra over 5–38 μm, and spectral energy distribution over 52–100 μm. The Spitzer archive contains targeted imaging observations for more than 100 PNe. Spitzer legacy surveys, particularly the GLIMPSE survey of the Galactic plane, contain additional serendipitous imaging observations of PNe. Spitzer imaging and spectroscopic observations of PNe allow us to investigate atomic/molecular line emission and dust continuum from the nebulae as well as circumstellar dust disks around the central stars. Highlights of Spitzer observations of PNe are reviewed in this paper.

scholarly journals The outer disk of the classical Be star ψ Per

2016 ◽  
Vol 12 (S329) ◽  
pp. 414-414
Author(s):  
Robert Klement ◽  
Alex C. Carciofi ◽  
Thomas Rivinius ◽  
Lynn D. Matthews ◽  
Richard Ignace ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Spectral Energy Distribution ◽  
Spectral Energy ◽  
Density Measurements ◽  
Outer Disk ◽  
Disk Size ◽  
Gaussian Fit ◽  
Be Star ◽  
Best Fit ◽  
Striking Contrast

AbstractTo this date ψ Per is the only classical Be star that was angularly resolved in radio (by the VLA at λ = 2 cm). Gaussian fit to the azimuthally averaged visibility data indicates a disk size (FWHM) of ~500 stellar radii (Dougherty & Taylor 1992). Recently, we obtained new multi-band cm flux density measurements of ψ Per from the enhanced VLA. We modeled the observed spectral energy distribution (SED) covering the interval from ultraviolet to radio using the Monte Carlo radiative transfer code HDUST (Carciofi & Bjorkman 2006). An SED turndown, that occurs between far-IR and radio wavelengths, is explained by a truncated viscous decretion disk (VDD), although the shallow slope of the radio SED suggests that the disk is not simply cut off, as is assumed in our model. The best-fit size of a truncated disk derived from the modeling of the radio SED is 100+5−15 stellar radii, which is in striking contrast with the result of Dougherty & Taylor (1992). The reasons for this discrepancy are under investigation.

scholarly journals J-PLUS: Synthetic galaxy catalogues with emission lines for photometric surveys

2019 ◽  
Vol 631 ◽  
pp. A82 ◽  
Author(s):  
David Izquierdo-Villalba ◽  
Raul E. Angulo ◽  
Alvaro Orsi ◽  
Guillaume Hurier ◽  
Gonzalo Vilella-Rojo ◽  
...  
Keyword(s):  
Emission Line ◽  
Narrow Band ◽  
Spectral Energy Distribution ◽  
Broad Band ◽  
Line Emission ◽  
Spectral Energy ◽  
Filter Method ◽  
Medium Band ◽  
Emission Line Galaxies ◽  
The Impact

We present a synthetic galaxy lightcone specially designed for narrow-band optical photometric surveys. To reduce time-discreteness effects, unlike previous works, we directly include the lightcone construction in the L-Galaxies semi-analytic model applied to the subhalo merger trees of the Millennium simulation. Additionally, we add a model for the nebular emission in star-forming regions, which is crucial for correctly predicting the narrow- and medium-band photometry of galaxies. Specifically, we consider, individually for each galaxy, the contribution of 9 different lines: Lyα (1216 Å), Hβ (4861 Å), Hα (6563 Å), [O II] (3727 Å, 3729 Å), [O III] (4959 Å, 5007 Å), [Ne III] (3870 Å), [O I] (6300 Å), [N II] (6548 Å, 6583 Å), and [S II] (6717 Å, 6731 Å). We validate our lightcone by comparing galaxy number counts, angular clustering, and Hα, Hβ, [O II], and [O III]5007 luminosity functions to a compilation of observations. As an application of our mock lightcones, we generated catalogues tailored for J-PLUS, a large optical galaxy survey featuring five broad-band and seven medium-band filters. We study the ability of the survey to correctly identify, with a simple three-filter method, a population of emission-line galaxies at various redshifts. We show that the 4000 Å break in the spectral energy distribution of galaxies can be misidentified as line emission. However, all significant excess (> 0.4 mag) can be correctly and unambiguously attributed to emission-line galaxies. Our catalogues are publicly released to facilitate their use in interpreting narrow-band surveys and in quantifying the impact of line emission in broad-band photometry.

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