scholarly journals The AGN Fraction in Dwarf Galaxies from eROSITA: First Results and Future Prospects

2021 ◽  
Vol 922 (2) ◽  
pp. L40
Author(s):  
Colin J. Latimer ◽  
Amy E. Reines ◽  
Akos Bogdan ◽  
Ralph Kraft
Keyword(s):  
Active Galactic Nuclei ◽  
Dwarf Galaxies ◽  
Dwarf Galaxy ◽  
High Redshift ◽  
Galactic Nuclei ◽  
Future Prospects ◽  
Massive Black Holes ◽  
X Ray ◽  
Sky Survey ◽  
First Results

Abstract Determining the fraction of nearby dwarf galaxies hosting massive black holes (BHs) can inform our understanding of the origin of “seed” BHs at high redshift. Here we search for signatures of accreting massive BHs in a sample of dwarf galaxies (M ⋆ ≤ 3 × 109 M ⊙, z ≤ 0.15) selected from the NASA-Sloan Atlas (NSA) using X-ray observations from the eROSITA Final Equatorial Depth Survey (eFEDS). On average, our search is sensitive to active galactic nuclei (AGNs) in dwarf galaxies that are accreting at ≳1% of their Eddington luminosity. Of the ∼28,000 X-ray sources in eFEDS and the 495 dwarf galaxies in the NSA within the eFEDS footprint, we find six galaxies hosting possible active massive BHs. If the X-ray sources are indeed associated with the dwarf galaxies, the X-ray emission is above that expected from star formation, with X-ray source luminosities of L 0.5–8 keV ∼ 1039–40 erg s−1. Additionally, after accounting for chance alignments of background AGNs with dwarf galaxies, we estimate there are between zero and nine real associations between dwarf galaxies and X-ray sources in the eFEDS field at the 95% confidence level. From this we find an upper limit on the eFEDS-detected dwarf galaxy AGN fraction of ≤1.8%, which is broadly consistent with similar studies at other wavelengths. We extrapolate these findings from the eFEDS sky coverage to the planned eROSITA All-Sky Survey and estimate that upon completion, the all-sky survey could yield as many as ∼1350 AGN candidates in dwarf galaxies at low redshift.

scholarly journals Active Galactic Nuclei in the Extreme Ultraviolet

1995 ◽  
Vol 10 ◽  
pp. 517-520
Author(s):  
Arieh Königl
Keyword(s):  
Active Galactic Nuclei ◽  
Extreme Ultraviolet ◽  
Galactic Nuclei ◽  
Transmission Factor ◽  
Similar Distribution ◽  
Hard Component ◽  
X Ray ◽  
Lack Of Information ◽  
Sky Survey ◽  
First Results

The extreme ultraviolet (EUV) wavelength interval (commonly defined to constitute the range 68 — 912 Å, or 13.6 — 182 eV) hes between the intensively studied FUV (912 - 3000 Å) and X-ray (1 - 68 Å) spectral regimes, but until recently has not been subjected to systematic investigations. This lack of information has been particularly acute in the case of active galactic nuclei (AGNs), where the very ability to carry out successful EUV observations has been seriously questioned. This has stemmed from the fact that, for a Galactic H I column density NG(H I) = 1 × 1020 cm−2, the interstellar transmission factor is 0.42 at 60 Å, but a factor of 10 smaller at 100 Å. In turn, there are no known regions of the interstellar medium (ISM) that have [NG(H I)/1020 cm−2] < 0.6 (resp., 0.8) for positive (resp., negative) latitudes (e.g., Heiles 1991).There are, however, several reasons why EUV observations of AGNs could provide important information about the nature of these objects. In the case of radio-quiet QSOs, the peak power is known to be emitted in the EUV range (several hundred A). Furthermore, in these sources there is evidence for a distinct soft X-ray component (representing a “soft excess” over an extrapolation of the ISM-absorbed hard X-ray component), whose properties are at present controversial. In particular, the first results of ROSAT PSPC observations of a complete sample of optically selected QSOs (Laor et al. 1994) have pointed to a spectral index αx = 1.50 ± 0.40 in the 0.2 − 2 keV range that flattens by Δαx ≈ 0.5 above ∽ 2 keV. This study has concluded that steep-αx sources are characterized by a week hard component. A similar distribution of αx has been inferred for soft X-ray-bright QSOs and Seyfert 1 galaxies observed in the ROSAT all-sky survey. On the other hand, previous observations (enumerated in Laor et al. 1994) by the Einstein and EXOSAT satellites yielded different soft X-ray spectral slopes and led to an alternative explanation of the steep-αχ objects. These questions could in principle be clarified by EUV measurements, which would then also help determine the soft X-ray emission mechanism.

scholarly journals Luminosity Correlation of the X-ray Selected Radio-Loud AGNs

1999 ◽  
Vol 194 ◽  
pp. 306-310
Author(s):  
Q. Yuan ◽  
J. Wu ◽  
K. Huang
Keyword(s):  
Active Galactic Nuclei ◽  
Broad Band ◽  
Galactic Nuclei ◽  
Radio Galaxies ◽  
Spectral Indices ◽  
Strong Correlations ◽  
Band Energy ◽  
X Ray ◽  
Sky Survey ◽  
Bl Lacs

This paper presents a test of the luminosity correlation of the X-ray selected radio-loud Active Galactic Nuclei (AGNs), based on a large sample constructed by combining our cross-identification of southern sky sources with the radio-loud sources in the northern hemisphere given by Brinkmann et al. (1995). All sources were detected both by the ROSAT All-Sky Survey and the radio surveys at 4.85 GHz. The broad band energy distribution confirms the presence of strong correlations between luminosities in the radio, optical, and X-ray bands which differ for quasars, seyferts, BL Lacs, and radio galaxies. The tight correlations between spectral indices αox and monochromatic luminosities at 5500 Å and 4.85 GHz are also shown.

SpitzerObservations of Optically “Invisible” Radio and X‐Ray Sources: High‐Redshift Active Galactic Nuclei

2005 ◽  
Vol 626 (1) ◽  
pp. 58-69 ◽  
Author(s):  
J. L. Higdon ◽  
S. J. U. Higdon ◽  
D. W. Weedman ◽  
J. R. Houck ◽  
E. Le Floc’h ◽  
...  
Keyword(s):  
Active Galactic Nuclei ◽  
High Redshift ◽  
Galactic Nuclei ◽  
X Ray

scholarly journals Powerful Water Masers in Active Galactic Nuclei

2002 ◽  
Vol 19 (4) ◽  
pp. 401-421 ◽  
Author(s):  
Philip R. Maloney
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Rotating Disk ◽  
Future Prospects ◽  
Maser Emission ◽  
X Ray ◽  
Central Engine ◽  
Water Masers ◽  
Water Maser

AbstractLuminous water maser emission in the 616–523 line at 22GHz has been detected from two dozen galaxies. In all cases the emission is confined to the nucleus and has been found only in AGN, in particular, in Type 2 Seyferts and LINERs. I argue that most of the observed megamaser sources are powered by X-ray irradiation of dense gas by the central engine. After briefly reviewing the physics of these X-Ray Dissociation Regions, I discuss in detail the observations of the maser disk in NGC 4258, its implications, and compare alternative models for the maser emission. I then discuss the observations of the other sources that have been imaged with VLBI to date, and how they do or do not fit into the framework of a thin, rotating disk, as in NGC 4258. Finally, I briefly discuss future prospects, especially the possibility of detecting other water maser transitions.

scholarly journals The hard X-ray luminosity function of high-redshift (3 < z ≲ 5) active galactic nuclei

2014 ◽  
Vol 445 (4) ◽  
pp. 3557-3574 ◽  
Author(s):  
F. Vito ◽  
R. Gilli ◽  
C. Vignali ◽  
A. Comastri ◽  
M. Brusa ◽  
...  
Keyword(s):  
Active Galactic Nuclei ◽  
Luminosity Function ◽  
High Redshift ◽  
Galactic Nuclei ◽  
X Ray

scholarly journals THE SPATIAL CLUSTERING OFROSATALL-SKY SURVEY ACTIVE GALACTIC NUCLEI. IV. MORE MASSIVE BLACK HOLES RESIDE IN MORE MASSIVE DARK MATTER HALOS

2015 ◽  
Vol 815 (1) ◽  
pp. 21 ◽  
Author(s):  
Mirko Krumpe ◽  
Takamitsu Miyaji ◽  
Bernd Husemann ◽  
Nikos Fanidakis ◽  
Alison L. Coil ◽  
...  
Keyword(s):  
Black Holes ◽  
Dark Matter ◽  
Active Galactic Nuclei ◽  
Spatial Clustering ◽  
Galactic Nuclei ◽  
Dark Matter Halos ◽  
Massive Black Holes ◽  
Sky Survey

scholarly journals The X‐Ray Spectral Properties and Variability of Luminous High‐Redshift Active Galactic Nuclei

2005 ◽  
Vol 630 (2) ◽  
pp. 729-739 ◽  
Author(s):  
O. Shemmer ◽  
W. N. Brandt ◽  
C. Vignali ◽  
D. P. Schneider ◽  
X. Fan ◽  
...  
Keyword(s):  
Active Galactic Nuclei ◽  
Spectral Properties ◽  
High Redshift ◽  
Galactic Nuclei ◽  
X Ray

scholarly journals THE EVOLUTION AND ENVIRONMENTS OF X-RAY EMITTING ACTIVE GALACTIC NUCLEI IN HIGH-REDSHIFT LARGE-SCALE STRUCTURES

2012 ◽  
Vol 746 (2) ◽  
pp. 155 ◽  
Author(s):  
N. Rumbaugh ◽  
D. D. Kocevski ◽  
R. R. Gal ◽  
B. C. Lemaux ◽  
L. M. Lubin ◽  
...  
Keyword(s):  
Active Galactic Nuclei ◽  
Large Scale ◽  
High Redshift ◽  
Galactic Nuclei ◽  
X Ray ◽  
Large Scale Structures ◽  
Scale Structures

scholarly journals Very High Redshift X-Ray–selected Active Galactic Nuclei in the Chandra Deep Field–North

2003 ◽  
Vol 584 (2) ◽  
pp. L61-L64 ◽  
Author(s):  
A. J. Barger ◽  
L. L. Cowie ◽  
P. Capak ◽  
D. M. Alexander ◽  
F. E. Bauer ◽  
...  
Keyword(s):  
Active Galactic Nuclei ◽  
High Redshift ◽  
Galactic Nuclei ◽  
X Ray ◽  
Very High

scholarly journals The impact of disturbed galaxy clusters on the kinematics of active galactic nuclei

2020 ◽  
Vol 499 (3) ◽  
pp. 3792-3805
Author(s):  
Lawrence E Bilton ◽  
Kevin A Pimbblet ◽  
Yjan A Gordon
Keyword(s):  
Active Galactic Nuclei ◽  
Galaxy Clusters ◽  
Velocity Dispersion ◽  
Signal To Noise Ratio ◽  
Galactic Nuclei ◽  
Sloan Digital Sky Survey ◽  
X Ray ◽  
Cluster Galaxies ◽  
Sky Survey ◽  
The Impact

ABSTRACT We produce a kinematic analysis of AGN-hosting cluster galaxies from a sample of 33 galaxy clusters selected using the X-ray Clusters Database (BAX) and populated with galaxies from the Sloan Digital Sky Survey Data Release 8. The 33 galaxy clusters are delimited by their relative intensity of member galaxy substructuring as a proxy to core merging to derive two smaller sub-samples of 8 dynamically active (merging) and 25 dynamically relaxed (non-merging) states. The AGN were selected for each cluster sub-sample by employing the WHAN diagram to the strict criteria of log10([N ii]/Hα) ≥ −0.32 and EWHα ≥ 6 Å, providing pools of 70 mergings and 225 non-merging AGN sub-populations. By co-adding the clusters to their respective dynamical states to improve the signal-to-noise ratio of our AGN sub-populations we find that merging galaxy clusters on average host kinematically active AGN between 0–1.5r200 as r200 → 0, where their velocity dispersion profile (VDP) presents a significant deviation from the non-AGN sub-population VDP by ≳3σ. This result is indicative that the AGN-hosting cluster galaxies have recently coalesced on to a common potential. Further analysis of the composite distributions illustrates non-merging AGN-hosting sub-populations have, on average, already been accreted and predominantly lie within backsplash regions of the projected phase-space. This suggests merging cluster dynamical states hold relatively younger AGN sub-populations kinematically compared with those found in non-merging cluster dynamical states.

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