We present a comprehensive data description for K sub(s)-band measurements of Sgr A*. We characterize the statistical properties of the variability of Sgr A* in the near-infrared, which we find to be ...consistent with a single-state process forming a power-law distribution of the flux density. We discover a linear rms-flux relation for the flux density range up to 12 mJy on a timescale of 24 minutes. This and the power-law flux density distribution implies a phenomenological, formally nonlinear statistical variability model with which we can simulate the observed variability and extrapolate its behavior to higher flux levels and longer timescales. We present reasons why data with our cadence cannot be used to decide on the question whether the power spectral density of the underlying random process shows more structure at timescales between 25 minutes and 100 minutes compared to what is expected from a red-noise random process.
Abstract
We present a study investigating the influence of jets on galaxies exhibiting strong O
iii
λ
5007 emission, known as
Green Peas
and
Green Beans
. Our sample comprised 12 nearby sources (
z
...∼ 0.04–0.1, six with jets and six without jets) with high O
iii
luminosity (
L
∼ 10
40
erg s
−1
), selected from a radio-selected galaxy sample observed with the Sloan Digital Sky Survey and Radio Sky at Twenty-centimeters survey. We perform Large Binocular Telescope–Multi-Object Double Spectrograph long-slit spectroscopy at two position angles for each galaxy: one aligned with the jet direction and another perpendicular to it. By tracing the O
iii
emission along these slits, we aimed to assess the extension of the narrow line region and examine the impact of jets. Surprisingly, our analysis revealed no preferred direction for the extension of the O
iii
emission, indicating that jets have a limited influence on the extended emission line regions (EELRs). This also suggests the possibility of missed detection of conical-shaped EELRs aligned with the jets, attributable to our slit orientations. Furthermore, we compared the extension of O
ii
emission, which traces star-forming regions, with that of O
iii
. We observed a significant difference, with O
ii
exhibiting a considerably greater extension along the galactic plane. This suggests a stronger association of O
ii
emission with stellar processes.
We probe the current-induced magnetic switching of insulating antiferromagnet–heavy-metal systems, by electrical spin Hall magnetoresistance measurements and direct imaging, identifying a reversal ...occurring by domain wall (DW) motion. We observe switching of more than one-third of the antiferromagnetic domains by the application of current pulses. Our data reveal two different magnetic switching mechanisms leading together to an efficient switching, namely, the spin-current induced effective magnetic anisotropy variation and the action of the spin torque on the DWs.
Context.
Several dusty infrared sources traced on their orbits around Sgr A* with SINFONI and NACO mounted at the VLT/Chile show near-infrared (NIR) excess and Doppler-shifted line emission. We ...investigate these sources in order to clarify their nature and compare their relationship to other observed NIR objects close to Sgr A*.
Aims.
Using SINFONI, we are able to determine the spectroscopic properties of the dusty infrared sources. Furthermore, we can extract spatial and velocity information of these objects. We are able to identify X7, X7.1, X8, G1, DSO/G2, D2, D23, D3, D3.1, D5, and D9 in the Doppler-shifted line maps of the SINFONI
H
+
K
data. From our
K
- and
L
′-band NACO data, we derive the related magnitudes of the brightest sources located west of Sgr A*.
Methods.
For determining the line of sight velocity information and to investigate single emission lines, we used the near-infrared integral field spectrograph SINFONI datasets between 2005 and 2015. For the kinematic analysis, we used NACO datasets from the years between 2002 and 2018. This study was done in the
H
,
K
s
, and
L
′ band. From the 3D SINFONI data-cubes, we extracted line maps in order to derive positional information for the sources. In the NACO images, we identified the dusty counterpart of the objects. When possible, we determined the Keplerian orbits and applied a photometric analysis.
Results.
The spectrum of the investigated objects show a Doppler-shifted Br
γ
and HeI line emission. For some objects west of Sgr A*, we additionally find FeIII line emission that can be clearly distinguished from the background. A one-component blackbody model fits the extracted near-infrared flux for the majority of the investigated objects, with the characteristic dust temperature of 500 K. The photometric derived
H
- and
K
S
-band magnitudes are between mag
H
> 22.5 and mag
k
= 18.1
+0.3
−0.8
for the dusty sources. For the
H
-band magnitudes we can provide an upper limit. For the bright dusty sources D2, D23, and D3, the Keplerian orbits are elliptical with a semi-major axis of
a
D2
= (749 ± 13) mas,
a
D23
= (879 ± 13), and
a
D3
= (880 ± 13) mas. For the DSO/G2, a single-temperature and a two-component blackbody model is fitted to the
H
-,
K
-,
L
′-, and
M
-band data, while the two-component model that consists of a star and an envelope fits its SED better than an originally proposed single-temperature dusty cloud.
Conclusions.
The spectroscopic analysis indicates that the investigated objects could be dust-embedded pre-main-sequence stars. The Doppler-shifted FeIII line can be spectroscopically identified in several sources that are located between 17:45:40.05 and 17:45:42.00 in Dec However, the sources with a DEC less than 17:45:40.05 show no FeIII emission. Therefore, these two groups show different spectroscopic features that could be explained by the interaction with a non-spherical outflow that originates at the position of Sgr A*. Following this, the hot bubble around Sgr A* consists out of isolated sources with FeIII line emission that can partially account for the previously detected FeIII distribution on larger scales.
In the framework of understanding the gas and stellar kinematics and their relations to AGNs and galaxy evolution scenarios, we present spatially resolved distributions and kinematics of the stars ...and gas in the central ∼800 pc radius of the nearby Seyfert galaxy NGC 1365. We obtained H + K- and K-band near-infrared (NIR) integral-field observations from VLT/SINFONI. Our results reveal strong broad and narrow emission-line components of ionized gas (hydrogen recombination lines Paα and Brγ) in the nuclear region, as well as hot dust with a temperature of ∼1300 K, both typical for type-1 AGNs. From MBH − σ* and the broad components of hydrogen recombination lines, we find a black-hole mass of (5 − 10)×106 M⊙. In the central ∼800 pc, we find a hot molecular gas mass of ∼615 M⊙, which corresponds to a cold molecular gas reservoir of (2 − 8)×108 M⊙. However, there is a molecular gas deficiency in the nuclear region. The gas and stellar-velocity maps both show rotation patterns consistent with the large-scale rotation of the galaxy. However, the gaseous and stellar kinematics show deviations from pure disk rotation, which suggest streaming motions in the central < 200 pc and a velocity twist at the location of the ring which indicates deviations in disk and ring rotation velocities in accordance with published CO kinematics. We detect a blueshifted emission line split in Paα, associated with the nuclear region only. We investigate the star-formation properties of the hot spots in the circumnuclear ring which have starburst ages of ≲10 Myr and find indications for an age gradient on the western side of the ring. In addition, our high-resolution data reveal further substructure within this ring which also shows enhanced star forming activity close to the nucleus.
Controlling magnetism by means of electric fields is a key issue for the future development of low-power spintronics. Progress has been made in the electrical control of magnetic anisotropy, domain ...structure, spin polarization or critical temperatures. However, the ability to turn on and off robust ferromagnetism at room temperature and above has remained elusive. Here we use ferroelectricity in BaTiO3 crystals to tune the sharp metamagnetic transition temperature of epitaxially grown FeRh films and electrically drive a transition between antiferromagnetic and ferromagnetic order with only a few volts, just above room temperature. The detailed analysis of the data in the light of first-principles calculations indicate that the phenomenon is mediated by both strain and field effects from the BaTiO3. Our results correspond to a magnetoelectric coupling larger than previous reports by at least one order of magnitude and open new perspectives for the use of ferroelectrics in magnetic storage and spintronics.
Context. The empirical relations between supermassive black holes and their host spheroids point towards the crucial role of galactic nuclei in affecting the properties of their hosts. A detailed ...understanding of how the activity of a galactic nucleus regulates the growth of its host is still missing. Aims. To understand the activity and the types of accretion of supermassive black holes in different hosts, it is essential to study the radio-optical properties of a large sample of extragalactic sources. In particular, we aim to study the radio spectral index trends across the optical emission line diagnostic diagrams to search for potential (anti)correlations. Methods. To this goal, we combined flux densities from the radio FIRST survey at 1.4 GHz (with the flux density range 10 mJy ≤ F1.4 ≤ 100 mJy) for 396 SDSS sources at intermediate redshift (0.04 ≤ z ≤ 0.4) with the Effelsberg radiotelescope measurements at 4.85 GHz and 10.45 GHz. The information about the optical emission-line ratios is obtained from the SDSS-DR7 catalogue. Results. Using the Effelsberg data, we were able to infer the two-point radio spectral index distributions for star-forming galaxies, composite galaxies (with a combined contribution to the line emission from the star formation and AGN activity), Seyferts, and low ionization narrow emission region (LINER) galaxies. Conclusions. While studying the distribution of steep, flat, and inverted sources across optical diagnostic diagrams, we found three distinct classes of radio emitters for our sample: (i) sources with a steep radio index, high ionization ratio, and high radio loudness, (ii) sources with a flat radio index, lower ionization ratio, and intermediate radio loudness, (iii) sources with an inverted radio index, low ionization ratio, and low radio loudness. The classes (i), (ii), and (iii) cluster mainly along the transition from Seyfert to LINER sources in the optical diagnostic (Baldwin, Phillips & Telervich; BPT) diagram. We interpret these groups as a result of the recurrent nuclear-jet activity.
We present a detailed analysis of the kinematics of 112 stars that mostly comprise the high-velocity S cluster and orbit the supermassive black hole Sgr A* at the center of the Milky Way. For 39 of ...them, orbital elements are known; for the remainder, we know proper motions. The distribution of the inclinations and the proper motion flight directions deviate significantly from a uniform distribution, which one expects if the orientation of the orbits are random. Across the central arcseconds, the S-cluster stars are arranged in two almost edge-on disks that are located at a position angle approximately 45° with respect to the Galactic plane. The angular momentum vectors for stars in each disk point in both directions, i.e., the stars in a given disk rotate in opposite ways. The poles of this structure are located only about 25° from the line of sight. This structure may be the result of a resonance process that started with the formation of the young B-dwarf stars in the cluster about 6 Myr ago. Alternatively, it indicated the presence of a disturber at a distance from the center comparable to the distance of the compact stellar association IRS 13.
A current drawback of spintronics is the large power that is usually required for magnetic writing, in contrast with nanoelectronics, which relies on "zero-current," gate-controlled operations. ...Efforts have been made to control the spin-relaxation rate, the Curie temperature, or the magnetic anisotropy with a gate voltage, but these effects are usually small and volatile. We used ferroelectric tunnel junctions with ferromagnetic electrodes to demonstrate local, large, and nonvolatile control of carrier spin polarization by electrically switching ferroelectric polarization. Our results represent a giant type of interfacial magnetoelectric coupling and suggest a low-power approach for spin-based information control.
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