scholarly journals The redshift and the host galaxy of the neutrino candidate 4FGL J0955.1+3551 (3HSP J095507.9+355101)

2020 ◽  
Vol 495 (1) ◽  
pp. L108-L111
Author(s):  
Simona Paiano ◽  
Renato Falomo ◽  
Paolo Padovani ◽  
Paolo Giommi ◽  
Adriana Gargiulo ◽  
...  
Keyword(s):  
Equivalent Width ◽  
Absolute Magnitude ◽  
Emission Lines ◽  
Absorption Lines ◽  
Host Galaxy ◽  
Source Image ◽  
Host Galaxies ◽  
Upper Limit ◽  
Bl Lac ◽  
Bl Lacs

ABSTRACT The BL Lac object 4FGL J0955.1+3551 has been suggested as a possible source of ultra-energetic neutrinos detected by the IceCube observatory. The target was observed in 2020 January at the Large Binocular Telescope. Our spectroscopy (4100–8500 Å) yields a firm redshift z = 0.557 as deduced by the absorption lines of the host galaxy. The upper limit of the minimum equivalent width on emission lines is ∼0.3 Å. From the source image, we are able to resolve the host galaxy for which we measure an absolute magnitude M(R) = −22.9 and Re = 8 kpc, which are values which are typical of the host galaxies of BL Lacs.

scholarly journals uGMRT detection of associated H i 21-cm absorption at z ≈ 3.5

2020 ◽  
Vol 500 (1) ◽  
pp. 998-1002
Author(s):  
J N H S Aditya ◽  
Regina Jorgenson ◽  
Vishal Joshi ◽  
Veeresh Singh ◽  
Tao An ◽  
...  
Keyword(s):  
Equivalent Width ◽  
Active Galactic Nucleus ◽  
Optical Spectrum ◽  
Significant Contribution ◽  
Neutral Hydrogen ◽  
Emission Lines ◽  
Host Galaxy ◽  
Width Ratio ◽  
Host Galaxies ◽  
Using Data

ABSTRACT We report a uGMRT (upgraded Giant Metrewave Radio Telescope) detection of H i 21-cm absorption associated with the radio source 8C 0604+728, at z = 3.52965. The source is at the highest redshift at which associated H i 21-cm absorption has been discovered to date, surpassing earlier known absorber at z ≈ 3.39. We estimate ultraviolet luminosities of $\rm (3.2 \pm 0.1) \times 10^{23}$ and $\rm (6.2 \pm 0.2)\times 10^{23}~W~Hz^{-1}$, and ionizing photon rates of $\rm (1.8 \pm 0.1) \times 10^{56}$ and $\rm (5.0 \pm 0.1) \times 10^{56}~s^{-1}$, using data at different epochs; the source shows year-scale variability in both its luminosity and photon rate. The luminosity and photon rate at later epochs are ≈6.2 and ≈1.7 times higher than thresholds suggested in the literature above which all the neutral hydrogen in the active galactic nucleus (AGN) host galaxy is expected to be ionized. The detection demonstrates that neutral hydrogen can survive in the host galaxies of AGNs with high ultraviolet luminosities. We estimate a high equivalent width ratio of 15.2 for the Lyman-α (Ly α) and He ii emission lines detected in the optical spectrum, which is consistent with AGN photoionization models. However, a significant contribution from young stellar populations to the excess Ly α flux cannot be ruled out.

Optical spectroscopy of BL Lac objects: TeV candidates

2020 ◽  
Vol 497 (1) ◽  
pp. 94-108 ◽  
Author(s):  
Simona Paiano ◽  
Renato Falomo ◽  
Aldo Treves ◽  
Riccardo Scarpa
Keyword(s):  
Lower Limit ◽  
Gamma Ray ◽  
Absorption Lines ◽  
Host Galaxies ◽  
Stellar Objects ◽  
Bl Lac Objects ◽  
Forbidden Transition ◽  
Bl Lac ◽  
Quasi Stellar Objects ◽  
Relationship Of

ABSTRACT We investigate the spectroscopic optical properties of gamma-ray sources detected with high significance above 50 GeV in the Third Catalog of Hard Fermi-LAT Sources and that are good candidates as TeV emitters. We focus on the 91 sources that are labelled by the Fermi team as BL Lac (BLL) objects or blazar candidates of uncertain type (BCUs), are in the Northern hemisphere, and are with unknown or uncertain redshift. We report here on GTC (Gran Telescopio Canarias) spectra (in the spectral range 4100–7750 Å) of 13 BCUs and 42 BLL objects. We are able to classify the observed targets as BLL objects and each source is briefly discussed. The spectra allowed us to determine the redshift of 25 objects on the basis of emission and/or absorption lines, finding 0.05 < z < 0.91. Most of the emission lines detected are due to forbidden transition of [O iii] and [N ii]. The observed line luminosity is found to be lower than that of quasi-stellar objects (QSOs) at similar continuum and could be reconciled with the line–continuum luminosity relationship of QSOs if a significant beaming factor is assumed. Moreover, for five sources we found intervening absorption lines that allow to set a spectroscopic lower limit of the redshift. For the remaining 25 sources, for which the spectra are lineless, a lower limit to z is given, assuming that the host galaxies are giant ellipticals.

scholarly journals Obscured AGN at 1.5 < z < 3.0 from the zCOSMOS-deep Survey

2019 ◽  
Vol 626 ◽  
pp. A9 ◽  
Author(s):  
M. Mignoli ◽  
A. Feltre ◽  
A. Bongiorno ◽  
F. Calura ◽  
R. Gilli ◽  
...  
Keyword(s):  
Physical Properties ◽  
Emission Line ◽  
Metal Content ◽  
High Redshift ◽  
Strong Relationship ◽  
Emission Lines ◽  
Host Galaxy ◽  
Host Galaxies ◽  
Uv Emission

Context. The physics and demographics of high-redshift obscured active galactic nuclei (AGN) is still scarcely investigated. New samples of such objects, selected with different techniques, can provide useful insights into their physical properties. Aims. With the goal to determine the properties of the gas in the emitting region of type 2 AGN, in particular, the gas metal content, we exploit predictions from photoionization models, including new parameterizations for the distance of gas distribution from the central source and internal microturbulence in the emitting clouds, to interpret rest-frame UV spectral data. Methods. We selected a sample of 90 obscured (type 2) AGN with 1.45 ≤ z ≤ 3.05 from the zCOSMOS-deep galaxy sample by 5σ detection of the high-ionization C IV λ1549 narrow emission line. This feature in a galaxy spectrum is often associated with nuclear activity, and the selection effectiveness has also been confirmed by diagnostic diagrams based on utraviolet (UV) emission-line ratios. We applied the same selection technique and collected a sample of 102 unobscured (type 1) AGN. Taking advantage of the large amount of multiband data available in the COSMOS field, we investigated the properties of the C IV-selected type 2 AGN, focusing on their host galaxies, X-ray emission, and UV emission lines. Finally, we investigated the physical properties of the ionized gas in the narrow-line region (NLR) of this type 2 AGN sample by combining the analysis of strong UV emission lines with predictions from photoionization models. Results. We find that in order to successfully reproduce the relative intensity of UV emission lines of the selected high-z type 2 AGN, two new ingredients in the photoionization models are fundamental: small inner radii of the NLR (≈90 pc for LAGN = 1045 erg s−1), and the internal dissipative microturbulence of the gas-emitting clouds (with vmicr ≈ 100 km s−1). With these modified models, we compute the gas-phase metallicity of the NLR, and our measurements indicate a statistically significant evolution of the metal content with redshift. Finally, we do not observe a strong relationship between the NLR gas metallicity and the stellar mass of the host galaxy in our C IV-selected type 2 AGN sample.

scholarly journals Velocity Offsets Due to Mass Outflows in Active Galaxies

2009 ◽  
Vol 5 (S267) ◽  
pp. 387-392
Author(s):  
D. M. Crenshaw ◽  
S. B. Kraemer ◽  
H. R. Schmitt ◽  
R. F. Mushotzky ◽  
J. P. Dunn
Keyword(s):  
Seyfert Galaxies ◽  
Emission Lines ◽  
Host Galaxy ◽  
Host Galaxies ◽  
Ionized Gas ◽  
Ngc 4151 ◽  
Spatially Resolved ◽  
Mass Outflow ◽  
Ngc 1068 ◽  
Narrow Emission

AbstractWe present a study of the radial velocity offsets between AGN-related narrow emission lines and host-galaxy emission and absorption lines in Seyfert galaxies with observed redshifts less than 0.043. We find that 35% of the Seyferts in the sample show [O iii] emission lines with blueshifts with respect to their host galaxies exceeding 50 km s−1, whereas only 6% show redshifts this large, in qualitative agreement with most previous studies. We also find that a greater percentage of Seyfert 1 galaxies show blueshifts than Seyfert 2 galaxies. Using HST/STIS spatially-resolved spectra of the Seyfert 2 galaxy NGC 1068 and the Seyfert 1 galaxy NGC 4151, we generate geometric models of their narrow-line regions (NLRs) and inner galactic disks and show how these models can explain the blueshifted [O iii] emission lines in collapsed STIS spectra of these two Seyferts. We conclude that the combination of mass outflow of ionized gas in the NLR and extinction by dust in the inner disk (primarily in the form of dust spirals) is primarily responsible for the velocity offsets in Seyfert galaxies.

scholarly journals Host galaxy line diagnostics for the candidate tidal disruption events XMMSL1 J111527.3+180638 and PTF09axc

2021 ◽  
Author(s):  
Anne Inkenhaag ◽  
Peter G Jonker ◽  
Giacomo Cannizzaro ◽  
Daniel Mata Sánchez ◽  
Richard D Saxton
Keyword(s):  
Active Galactic Nucleus ◽  
Seyfert Galaxy ◽  
Emission Lines ◽  
Host Galaxy ◽  
Host Galaxies ◽  
Colour Difference ◽  
Tidal Disruption ◽  
Star Forming ◽  
Extreme Variability ◽  
Dusty Torus

Abstract We present results of our analysis of spectra of the host galaxies of the candidate Tidal Disruption Events (TDEs) XMMSL1 J111527.3+180638 and PTF09axc to determine the nature of these transients. We subtract the starlight component from the host galaxy spectra to determine the origin of the nuclear emission lines. Using a Baldwin–Phillips–Terlevich (BPT) diagram we conclude that the host galaxy of XMMSL1 J111527.3+180638 is classified as a Seyfert galaxy, suggesting this transient is likely to be caused by (extreme) variability in the active galactic nucleus. We find that the host of PTF09axc falls in the ’star-forming’ region of the BPT-diagram, implying that the transient is a strong TDE candidate. For both galaxies we find a WISE-colour difference of W1 − W2 &lt; 0.8, which means there is no indication of a dusty torus and therefore an active galactic nucleus, seemingly contradicting our BPT finding for the host of XMMSL1 J111527.3+180638. We discuss possible reasons for the discrepant results obtained through the two methods.

scholarly journals Quasar activity in the neighbor Universe

2012 ◽  
Vol 8 (S295) ◽  
pp. 268-268
Author(s):  
R. Falomo ◽  
D. Bettoni ◽  
K. Karhunen ◽  
J. Kotilainen ◽  
M. Uslenghi
Keyword(s):  
Black Hole ◽  
Radio Emission ◽  
Absolute Magnitude ◽  
Host Galaxy ◽  
Black Hole Mass ◽  
Host Galaxies ◽  
Preliminary Results ◽  
Galaxy Model ◽  
The Mean

AbstractWe investigate the properties of the galaxies hosting quasars in ~400 low redshift (z < 0.5) SDSS QSO that are in the “Stripe 82” sky area. For this region deep (r ~ 22.4 mag) u, b, v, r and i images are available and allow us to study both the host galaxies and the Mpc scale environments. This sample outnumbers previous studies of low-z QSOs. We present preliminary results of the properties of quasars activity and in particular we focus on the relationships among host galaxy luminosity, black hole mass, radio emission and the surrounding galaxy environments. We select from the SDSS - QSO Catalogue all the QSOs in the range of redshift 0.1<z<0.5 and in the Stripe82 region. This gives a total of 416 QSO. In this sample we are dominated by radio quiet quasars (about 5% are radio loud). In Fig. 1 we report the distribution of QSO in the plane redshift-MR (H0 = 70). The mean redshift of the sample is <z> = 0.39 and the average absolute magnitude is: <Mi> = −22.68. We implemented an automated procedure using AIDA (Uslenghi & Falomo 2011) to decompose the QSO images into nucleus and host galaxy luminosity. After masking of all contaminating sources in the field a 2D fitting is performed using PSF + galaxy model. In Fig. 1 we show an example of a QSO image in the sample and the distribution of the host galaxy absolute magnitude of the resolved objects.

The Influence of Selection Effects on the Properties of BL Lacs

1994 ◽  
Vol 159 ◽  
pp. 515-515
Author(s):  
M.J.M. Marchã ◽  
I.W.A. Browne
Keyword(s):  
Optical Emission ◽  
Statistical Properties ◽  
Host Galaxy ◽  
Selection Effects ◽  
X Ray ◽  
Luminous Galaxies ◽  
Bl Lac ◽  
Bl Lacs

The fact that the recognition of BL Lacs always requires optical confirmation, regardless of whether the objects were first selected in the radio, or X-ray frequencies means that deep surveys will miss some objects simply because the optical emission from the host galaxy outshines that of the BL Lac. In particular, the deeper the survey, the more difficult it will become to recognize low luminosity BL Lacs in the nuclei of luminous galaxies. This recognition effect will modify the intrinsic distribution of objects, and influence their statistical properties in general.

A Search for HI Absorption in the Radio Spectra of the Quasi-Stellar Objects 4C 05.34 and PKS 0237-23

1975 ◽  
Vol 2 (6) ◽  
pp. 365-366 ◽  
Author(s):  
B.A. Peterson ◽  
J.D. Murray ◽  
A.E. Wright
Keyword(s):  
Emission Line ◽  
Intergalactic Medium ◽  
Mass Density ◽  
Emission Lines ◽  
Absorption Lines ◽  
Stellar Objects ◽  
Upper Limit ◽  
Quasi Stellar Objects ◽  
No Absorption

The ratio of the mass density in visible galaxies to the upper limit for the HI mass density determined from the lack of continuous Ly-α absorption in QSO spectra is 3 × 104. Thus, if galaxies form by condensation from an intergalactic medium, the process must be extremely efficient. Although no absorption due to a continuous distribution of intergalactic HI has been detected, many QSOs have been discovered that have absorption lines in their spectra, which have redshifts very different from the emission lines, and may be produced in clouds of integalactic HI. As would be expected if this were the case, the proportion of QSOs with absorption lines in their spectra is greatest for those which have large emission line redshifts. Another possibility, especially for those absorption lines in redshift systems with Zabs nearly equal to Zem , is that the absorption lines are produced in clouds surrounding the QSO.

scholarly journals Can BL Lac Nuclei and Broad Line Regions Coexist? or When is an Object a BL Lac?

1996 ◽  
Vol 175 ◽  
pp. 244-245
Author(s):  
M.J.M. Marchã
Keyword(s):  
Selection Criteria ◽  
Radio Spectrum ◽  
Emission Lines ◽  
Systematic Analysis ◽  
Object A ◽  
Bl Lac ◽  
Optical Continuum ◽  
Common Criterion ◽  
Definition Of ◽  
Bl Lacs

The problem of BL Lac classification is a long standing one and it is mainly due to the subjectiveness of selection criteria used in the definition of BL Lac samples. For instance, an object will undoubtedly be classified as a BL Lac if it shows flat radio spectrum, high optical and radio polarization, featureless optical continuum with weak or absent emission lines, and variable flux and polarization. However, the problem arises when the object shows some but not all of these properties. In face of this difficulty, different authors (Stickel et al. 1991, Stocke et al. 1991) have tried to make a systematic analysis of the data and it has been common to classify as BL Lacs those objects whose strongest emission lines have equivalent width (EW) ≤ 5 Å. Another common criterion is to require the 4000 Å break contrast to be ≤ 0.25. Nevertheless, both of these criteria are rather arbitrary and more directly related to practical observational considerations, than they are to any physical distinction between objects. What is proposed here is a slightly different approach; it is proposed that we take a step back from common classification and that instead of imposing strict selection criteria, we create a multi-observational parameter space to investigate any breaks in the distribution of observed properties that will help clarify the distinction between BL Lacs and other flat radio spectrum sources.

scholarly journals Host galaxy properties of changing-look AGNs revealed in the MaNGA survey

2020 ◽  
Vol 498 (3) ◽  
pp. 3985-3994
Author(s):  
Xiaoling Yu ◽  
Yong Shi ◽  
Yanmei Chen ◽  
Jianhang Chen ◽  
Songlin Li ◽  
...  
Keyword(s):  
Active Galactic Nuclei ◽  
Main Sequence ◽  
Galactic Nuclei ◽  
Axial Ratio ◽  
Emission Lines ◽  
Host Galaxy ◽  
Type I ◽  
Host Galaxies ◽  
Star Forming ◽  
Nearby Galaxies

ABSTRACT Changing-look active galactic nuclei (CL-AGNs) are a subset of AGNs in which the broad Balmer emission lines appear or disappear within a few years. We use the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey to identify five CL-AGNs. The 2D photometric and kinematic maps reveal common features as well as some unusual properties of CL-AGN hosts as compared to the AGN hosts in general. All MaNGA CL-AGNs reside in the star-forming main sequence, similar to MaNGA non-changing-look AGNs (NCL-AGNs). The $80 \pm 16{{\ \rm per\ cent}}$ of our CL-AGNs do possess pseudo-bulge features, and follow the overall NCL-AGN MBH–σ* relationship. The kinematic measurements indicate that they have similar distributions in the plane of angular momentum versus galaxy ellipticity. MaNGA CL-AGNs, however, show a higher, but not statistically significant ($20 \pm 16{{\ \rm per\ cent}}$) fraction of counter-rotating features compared to that ($1.84 \pm 0.61{{\ \rm per\ cent}}$) in general star formation population. In addition, MaNGA CL-AGNs favour more face-on (axial ratio &gt; 0.7) than that of type I NCL-AGNs. These results suggest that host galaxies could play a role in the CL-AGN phenomenon.

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