scholarly journals Dust and star formation in the centre of NGC 3311

2020 ◽  
Vol 643 ◽  
pp. A119 ◽  
Author(s):  
T. Richtler ◽  
M. Hilker ◽  
M. Arnaboldi ◽  
C. E. Barbosa
Keyword(s):  
Star Formation ◽  
Emission Line ◽  
Globular Clusters ◽  
Stellar Population ◽  
Line Emission ◽  
Galaxy Cluster ◽  
Emission Lines ◽  
Strong Line ◽  
Rotating Disc ◽  
Neutral Gas

Context. NGC 3311 is the central galaxy of the Hydra I galaxy cluster. It has a hot interstellar medium and hosts a central dust lane with emission lines. These dust lanes are frequent in elliptical galaxies, but the case of NGC 3311 might be particularly interesting for problems of dust lifetime and the role of cool gas in the central parts. Aims. We aim to use archival HST images and MUSE data to investigate the central dust structure of NGC 3311. Methods. We used the tool PyParadise to model the stellar population and extract the emission lines. Results. The HST/ACS colour map reveals the known dust structures, but also blue spots, which are places of strong line emission. A dusty “mini-jet” emanates from the centre. The distribution of the emission line gas matches the dust silhouette almost exactly. Close to the brightest Hα emission, the ratio [NII]/Hα resembles that of HII-regions; in the outer parts, [NII] gets stronger and is similar to LINERLow-ionization nuclear emission-line region -like spectra. The gas kinematics is consistent with that of a rotating disc. The Doppler shifts of the strongest line emissions, which indicate the areas of highest star formation activity, smoothly fit into the disc symmetry. The metallicity is supersolar. The presence of neutral gas is indicated by the fit residuals of the stellar NaI D absorption line, which we interpret as interstellar absorption. We estimate the mass of the neutral gas to be of the order of the X-ray mass. The dynamical mass infers a stellar population of intermediate age, whose globular clusters have already been identified. Conclusions. Our findings can be harmonised in a scenario in which the star formation is triggered by the accretion of cold gas onto a pre-existing gas/dust disc or ring. Newly produced dust then contributes to the longevity of the dust.

scholarly journals UV emission line studies of NGC-low redshift Seyfert Galaxies, LINERS and HII regions

2017 ◽  
Vol 16 (1) ◽  
pp. 25-43
Author(s):  
Vedavathi P ◽  
Vijayakumar H Doddamani
Keyword(s):  
Emission Line ◽  
Spectral Data ◽  
High Redshift ◽  
Line Emission ◽  
Seyfert Galaxies ◽  
Uv Spectra ◽  
Active Galaxies ◽  
Emission Lines ◽  
Strong Line ◽  
Continuum Source

Active galaxies as a special class of galaxies are characterized by very strong and broad emission lines. The strong emission lines such as Lyα, NV, Si IV, C IV, and Mg II observed in the UV spectra of Seyfert galaxies and quasars can be used to probe the physical conditions of the gas in the BLR regions surrounding the central accretion discs of these most luminous and exotic objects. In the standard model of broad line emission regions for active galaxies it is assumed that the broad permitted lines are emitted by the photo-ionization of a large number of spherically distributed optically thick clouds which are in Keplerian motion surrounding a central continuum source. However, issues related to variability time-scales, delays in the light curves and BLR sizes etc., remain unexplained consistent with observations.  In this paper, a study of emission line properties 9 objects satisfying good SNR (> 5.0) out of 98 NGC (catalogued) IUE observed low redshift active galaxies (z ≤ 0.017) is presented. The International Ultraviolet Explorer (IUE) satellite launched in 1978 by NASA has made low redshift UV spectroscopic observations of many different kinds of UV sources including active galaxies till 1996 and the flux calibrated spectral data of almost all observations have been hosted in NED-IUE database. In the present studies, IUE spectral data of a complete sample of NGC-catalogued active galaxies has been undertaken to understand the emission line properties of low luminosity and low z active galaxies. We find that the emission lines such as Lyα, N V, Si IV, O III], C III], C IV, and Mg II are observed as strong and broad lines in the spectra of only 9 objects owing to the criterion of S/N ≥ 5.0 adopted for the spectral analysis. The Lyα has not been found to be a strong line unlike in high z Seyfert galaxies and quasars observed by IUE satellite. C IV and Mg II lines are observed to be stronger lines in all the nine objects consistent with their usual presence in the remaining (~ 400) active galaxies observed by the IUE satellite. These observations are indicative of different physical and geometrical conditions in the BLR regions surrounding the central accretion disk compared to the intermediate and high redshift Seyfert galaxies and quasars.

scholarly journals Challenges and Techniques for Simulating Line Emission

Galaxies ◽  
2018 ◽  
Vol 6 (4) ◽  
pp. 100 ◽  
Author(s):  
Karen Olsen ◽  
Andrea Pallottini ◽  
Aida Wofford ◽  
Marios Chatzikos ◽  
Mitchell Revalski ◽  
...  
Keyword(s):  
Interstellar Medium ◽  
Emission Line ◽  
Line Emission ◽  
Emission Lines ◽  
Synthetic Spectra ◽  
Recent Advances ◽  
The Future ◽  
Important Quality ◽  
Circumgalactic Medium

Modeling emission lines from the millimeter to the UV and producing synthetic spectra is crucial for a good understanding of observations, yet it is an art filled with hazards. This is the proceedings of “Walking the Line”, a 3-day conference held in 2018 that brought together scientists working on different aspects of emission line simulations, in order to share knowledge and discuss the methodology. Emission lines across the spectrum from the millimeter to the UV were discussed, with most of the focus on the interstellar medium, but also some topics on the circumgalactic medium. The most important quality of a useful model is a good synergy with observations and experiments. Challenges in simulating line emission are identified, some of which are already being worked upon, and others that must be addressed in the future for models to agree with observations. Recent advances in several areas aiming at achieving that synergy are summarized here, from micro-physical to galactic and circum-galactic scale.

scholarly journals Modeling Line Emission from Disk Winds

2009 ◽  
Vol 5 (S267) ◽  
pp. 398-398
Author(s):  
Patrick B. Hall ◽  
Laura S. Chajet
Keyword(s):  
Emission Line ◽  
Accretion Disk ◽  
Line Emission ◽  
Emission Lines ◽  
Broad Emission

Murray & Chiang (1997) developed a model wherein broad emission lines come from the optically thick base of a rotating, outwardly accelerating wind at the surface of an accretion disk. Photons preferentially escape radially in such a wind, explaining why broad emission lines are usually single-peaked. Less well understood are the observed shifts of emission-line peaks (from 1000 km s−1 redshifted to 2500 km s−1 blueshifted in C iv, with an average 800 km s−1 blueshift).

scholarly journals Discovery of diffuse optical emission lines from the inner Galaxy: Evidence for LI(N)ER-like gas

2020 ◽  
Vol 6 (27) ◽  
pp. eaay9711 ◽  
Author(s):  
D. Krishnarao ◽  
R. A. Benjamin ◽  
L. M. Haffner
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Center ◽  
Line Emission ◽  
Galactic Nuclei ◽  
Optical Emission ◽  
Hydrogen Gas ◽  
Emission Lines ◽  
Neutral Gas ◽  
Optical Line ◽  
Tilted Disk

Optical emission lines are used to categorize galaxies into three groups according to their dominant central radiation source: active galactic nuclei, star formation, or low-ionization (nuclear) emission regions [LI(N)ERs] that may trace ionizing radiation from older stellar populations. Using the Wisconsin H-Alpha Mapper, we detect optical line emission in low-extinction windows within eight degrees of Galactic Center. The emission is associated with the 1.5-kiloparsec-radius “Tilted Disk” of neutral gas. We modify a model of this disk and find that the hydrogen gas observed is at least 48% ionized. The ratio [NII] λ6584 angstroms/Hα λ6563 angstroms increases from 0.3 to 2.5 with Galactocentric radius; [OIII] λ5007 angstroms and Hβ λ4861 angstroms are also sometimes detected. The line ratios for most Tilted Disk sightlines are characteristic of LI(N)ER galaxies.

scholarly journals Deep HST Imaging of a Galaxy Cluster at z = 2.40

1996 ◽  
Vol 171 ◽  
pp. 474-475
Author(s):  
Rogier A. Windhorst ◽  
Sam M. Pascarelle ◽  
William C. Keel
Keyword(s):  
Star Formation ◽  
Stellar Population ◽  
Radio Galaxy ◽  
Narrow Band ◽  
Galaxy Cluster ◽  
Narrow Line ◽  
Color Plate ◽  
Band Emission ◽  
Physical Scale ◽  
Line Galaxy

We present a 67-orbit HST/WFPC2 exposure on the weak radio galaxy 53W002 at z=2.390 and its surrounding cluster. Color Plate 1 shows 12 orbits in IF814W & VF606W, and 24 in BF450W. Potential cluster members were identified through 15 orbits in F410M, optimized for narrow-band searches for compact Lyα objects at z≃2.4 (P96), and confirmed through spectroscopy (W91, P96); 16 candidates were found with significant narrow-band emission in F410M: 4 out of 5 had a confirming MMT spectroscopic redshift at z≃2.40 (P96). All are located within 60″ from 53W002, or ∼ 0.24h–1100 Mpc (qo=0.5) at z ≃2.4, the physical scale of a group or small galaxy cluster. One object contains a weak (variable) AGN, another is a merger with two companions. Their underlying young stellar population is very compact, with rh.l. ≃0.2″ (≃ 0.8h–1100 kpc), and considerably fainter than the L∗-value at z∼2.4, implying sub-galactic sized objects. These results may explain why ground-based Lya searches for PG's have been largely unsuccessful. The narrow-line galaxy 53W002 was imaged in the PC at ∼0.07″ FWHM (WK95, see also W94). Its AGN component is ≤ 20±4% of the total continuum, surrounded by an extended r1/4-envelope with rh.l. ≃1.1″ (4.3 kpc), and has an SED of ∼0.3 Gyr in the center to ∼0.5-1.0 Gyr at ∼4 kpc. A one-sided cloud is seen ∼1.8 kpc West, ∼0.3 mag bluer than the SED, aligned with the radio source and its Ly-α cloud, presumably weak scattered AGN light, and/or jet-induced star-formation.

scholarly journals A stellar census in globular clusters with MUSE: A spectral catalogue of emission-line sources

2019 ◽  
Vol 631 ◽  
pp. A118 ◽  
Author(s):  
Fabian Göttgens ◽  
Tim-Oliver Husser ◽  
Sebastian Kamann ◽  
Stefan Dreizler ◽  
Benjamin Giesers ◽  
...  
Keyword(s):  
Emission Line ◽  
Binary Stars ◽  
Globular Clusters ◽  
Cataclysmic Variables ◽  
Variable Stars ◽  
Emission Lines ◽  
Data Set ◽  
Stellar Spectra ◽  
X Ray ◽  
Emission Line Galaxies

Aims. Globular clusters produce many exotic stars due to a much higher frequency of dynamical interactions in their dense stellar environments. Some of these objects were observed together with several hundred thousand other stars in our MUSE survey of 26 Galactic globular clusters. Assuming that at least a few exotic stars have exotic spectra (i.e. spectra that contain emission lines), we can use this large spectroscopic data set of over a million stellar spectra as a blind survey to detect stellar exotica in globular clusters. Methods. To detect emission lines in each spectrum, we modelled the expected shape of an emission line as a Gaussian curve. This template was used for matched filtering on the differences between each observed 1D spectrum and its fitted spectral model. The spectra with the most significant detections of Hα emission are checked visually and cross-matched with published catalogues. Results. We find 156 stars with Hα emission, including several known cataclysmic variables (CV) and two new CVs, pulsating variable stars, eclipsing binary stars, the optical counterpart of a known black hole, several probable sub-subgiants and red stragglers, and 21 background emission-line galaxies. We find possible optical counterparts to 39 X-ray sources, as we detected Hα emission in several spectra of stars that are close to known positions of Chandra X-ray sources. This spectral catalogue can be used to supplement existing or future X-ray or radio observations with spectra of potential optical counterparts to classify the sources.

scholarly journals Spatially resolved properties of galaxies with a kinematically distinct core

2021 ◽  
Vol 647 ◽  
pp. A181
Author(s):  
Kiyoaki Christopher Omori ◽  
Tsutomu T. Takeuchi
Keyword(s):  
Star Formation ◽  
Emission Line ◽  
Stellar Population ◽  
Main Body ◽  
Stellar Kinematics ◽  
Stellar Core ◽  
Spatially Resolved ◽  
Star Formation Histories ◽  
Inside Out ◽  
Detailed Picture

Aims. Interacting galaxies show unique irregularities in their kinematic structures. By investigating the spatially resolved kinematics and stellar population properties of galaxies that demonstrate irregularities, we can paint a detailed picture of the formation and evolutionary processes that took place during their lifetimes. Methods. In this work, we focused on galaxies with a specific kinematic irregularity: a kinematically distinct stellar core (KDC). In particular, we considered counter-rotating galaxies in which the core and main body of are rotating in opposite directions. We visually identified 11 MaNGA galaxies with a KDC from their stellar kinematics, and we investigated their spatially resolved stellar and gaseous kinematic properties, namely the two-dimensional stellar and gaseous velocity and velocity-dispersion (σ) maps. Additionally, we examined the stellar population properties, as well as spatially resolved recent star formation histories, using the Dn4000 and Hδ gradients. Results. The galaxies display multiple off-centred symmetrical peaks in the stellar σ maps. The gaseous velocity and σ maps display regular properties. The stellar population properties and their respective gradients show differing properties depending on the results of the spatially resolved emission line diagnostics of the galaxies, with some but not all galaxies showing inside-out quenching. The star formation histories also largely differ based on the spatially resolved emission line diagnostics, but most galaxies show indications of recent star formation either in their outskirts or core. Conclusions. We find a distinct difference in kinematic and stellar population properties in galaxies with a counter-rotating stellar core, which depends on its classification using spatially resolved emission line diagnostics.

scholarly journals The ultra-diffuse galaxy NGC 1052-DF2 with MUSE

2019 ◽  
Vol 625 ◽  
pp. A77 ◽  
Author(s):  
Jérémy Fensch ◽  
Remco F. J. van der Burg ◽  
Tereza Jeřábková ◽  
Eric Emsellem ◽  
Anita Zanella ◽  
...  
Keyword(s):  
Globular Clusters ◽  
Stellar Population ◽  
Spectroscopic Analysis ◽  
Emission Lines ◽  
Spectral Fitting ◽  
Spatially Extended ◽  
The Subject ◽  
Stellar Body ◽  
Extended Emission ◽  
Intense Debate

NGC 1052-DF2, an ultra-diffuse galaxy (UDG), has been the subject of intense debate. Its alleged absence of dark matter, and the brightness and number excess of its globular clusters (GCs) at an initially assumed distance of 20 Mpc suggest a new formation channel for UDGs. We present the first systematic spectroscopic analysis of the stellar body and the GCs in this galaxy (six previously known and one newly confirmed member) using MUSE at the VLT. Even though NGC 1052-DF2 does not show any spatially extended emission lines, we report the discovery of three planetary nebulae (PNe). We conduct full spectral fitting on the UDG and the stacked spectra of all the GCs. The UDG’s stellar population is old, 8.9 ± 1.5 Gyr; metal poor, [M/H] = −1.07 ± 0.12; and with little or no α-enrichment. The stacked spectrum of all GCs indicates a similar age of 8.9 ± 1.8 Gyr, but a lower metallicity of [M/H] = −1.63 ± 0.09 and a similarly low α-enrichment. There is no evidence for a variation in age and metallicity in the GC population with the available spectra. The significantly more metal-rich stellar body with respect to its associated GCs, the age of the population, its metallicity, and its α-enrichment are all in line with other dwarf galaxies. NGC 1052-DF2 thus falls on the same empirical mass–metallicity relation as other dwarfs for the full distance range assumed in the literature. We find that both debated distance estimates (13 and 20 Mpc) are similarly likely, given the three discovered PNe.

scholarly journals Probing cosmic dawn with emission lines: predicting infrared and nebular line emission for ALMA and JWST

2019 ◽  
Vol 487 (4) ◽  
pp. 5902-5921 ◽  
Author(s):  
Harley Katz ◽  
Thomas P Galligan ◽  
Taysun Kimm ◽  
Joakim Rosdahl ◽  
Martin G Haehnelt ◽  
...  
Keyword(s):  
High Redshift ◽  
Formation Rate ◽  
Line Emission ◽  
Emission Lines ◽  
Strong Line ◽  
Radiation Hydrodynamics ◽  
High Redshift Galaxies ◽  
Physical Conditions ◽  
Velocity Gradients ◽  
Ionization Parameter

ABSTRACT Infrared and nebular lines provide some of our best probes of the physics regulating the properties of the interstellar medium (ISM) at high redshift. However, interpreting the physical conditions of high-redshift galaxies directly from emission lines remains complicated due to inhomogeneities in temperature, density, metallicity, ionization parameter, and spectral hardness. We present a new suite of cosmological, radiation-hydrodynamics simulations, each centred on a massive Lyman-break galaxy that resolves such properties in an inhomogeneous ISM. Many of the simulated systems exhibit transient but well-defined gaseous discs that appear as velocity gradients in [C ii] 157.6 $\mu$m emission. Spatial and spectral offsets between [C ii] 157.6 $\mu$m and [O iii] 88.33 $\mu$m are common, but not ubiquitous, as each line probes a different phase of the ISM. These systems fall on the local [C ii]–SFR relation, consistent with newer observations that question previously observed [C ii] 157.6 $\mu$m deficits. Our galaxies are consistent with the nebular line properties of observed z ∼ 2–3 galaxies and reproduce offsets on the BPT and mass-excitation diagrams compared to local galaxies due to higher star formation rate (SFR), excitation, and specific-SFR, as well as harder spectra from young, metal-poor binaries. We predict that local calibrations between H α and [O ii] 3727$\, \mathring{\rm A}$ luminosity and galaxy SFR apply up to z > 10, as do the local relations between certain strong line diagnostics (R23 and [O iii] 5007$\, \mathring{\rm A}$/H β) and galaxy metallicity. Our new simulations are well suited to interpret the observations of line emission from current (ALMA and HST) and upcoming facilities (JWST and ngVLA).

scholarly journals Star Formation in Damped Lyman α Selected Galaxies

2007 ◽  
Vol 3 (S244) ◽  
pp. 284-288
Author(s):  
Lise Christensen
Keyword(s):  
Star Formation ◽  
Emission Line ◽  
High Redshift ◽  
Neutral Hydrogen ◽  
Disk Galaxies ◽  
Local Universe ◽  
High Redshift Galaxies ◽  
Neutral Gas ◽  
Integral Field Spectroscopy ◽  
Integral Field

AbstractI present results from an ongoing survey to study galaxies associated with damped Lyman-α (DLA) systems at redshifts z>2. Integral field spectroscopy is used to search for Lyα emission line objects at the wavelengths where the emission from the quasars have been absorbed by the DLAs. The DLA galaxy candidates detected in this survey are found at distances of 10–20 kpc from the quasar line of sight, implying that galaxies are surrounded by neutral hydrogen at large distances. If we assume that the distribution of neutral gas is exponential, the scale length of the neutral gas is ~6 kpc, similar to large disk galaxies in the local Universe. The emission line luminosities imply smaller star formation rates compared to other high redshift galaxies found in luminosity selected samples.

Sign in / Sign up

Export Citation Format

Share Document