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2751. Origins of radio emission in NLS1s
ID:
ivo://CDS.VizieR/J/A+A/658/A12
Title:
Origins of radio emission in NLS1s
Short Name:
J/A+A/658/A12
Date:
02 Feb 2022 14:01:48
Publisher:
CDS
Description:
Narrow-line Seyfert 1 galaxies (NLS1s) are believed to be active galactic nuclei (AGN) in the early stages of their evolution. Several dozen of them have been found to host relativistic jets, whilst the majority of NLS1s have not even been detected in radio, emphasising the heterogeneity of the class in this band. In this paper, our aim is to determine the predominant source of radio emission in a sample of 44 NLS1s, selected based on their extended kiloparsec-scale radio morphologies at 5.2GHz. We accomplish this by analysing their spatially resolved radio spectral index maps, centred at 5.2 GHz, as the spectral index carries information about the production mechanisms of the emission. In addition, we utilise several diagnostics based on mid-infrared emission to estimate the star formation activity of their host galaxies. These data are complemented by archival data to draw a more complete picture of each source. We find an extraordinary diversity among our sample. Approximately equal fractions (~10-12 sources) of our sources can be identified as AGN-dominated, composite, and host-dominated. Among the AGN-dominated sources are a few NLS1s with very extended jets, reaching distances of tens of kiloparsecs from the nucleus. One of these, J0814+5609, hosts the most extended jets found in an NLS1 so far. We also identify five NLS1s that could be classified as compact steep-spectrum sources. In addition, one source shows a possible kiloparsec-scale relic that reaches well outside the host galaxy as well as restarted nuclear activity, and one could belong to the sub-class of NLS1s that host relativistic jets that seem to be absorbed at lower radio frequencies (<10GHz). We further conclude that, due to the variety seen in NLS1s, simple proxies, such as the star formation diagnostics also employed in this paper and the radio loudness parameter, are not ideal tools for characterising NLS1s. We emphasise the necessity of examining NLS1s as individuals instead of making assumptions based on their classification. When these issues are properly taken into account, NLS1s offer an exceptional environment for studying the interplay between the host galaxy and several AGN-related phenomena, such as jets and outflows.
2752. Outer disks of S0-Sb gal. II. Surface-brigthness
ID:
ivo://CDS.VizieR/J/AJ/142/145
Title:
Outer disks of S0-Sb gal. II. Surface-brigthness
Short Name:
J/AJ/142/145
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present azimuthally averaged radial profiles of R-band surface brightness for a complete sample of 47 early-type, unbarred galaxies, as a complement to our previous study of early-type barred galaxies. Following very careful sky subtraction, the profiles can typically be determined down to brightness levels well below 27mag/arcsec^2^ and in the best cases below 28mag/arcsec^-2^. We classified the profiles according to the scheme used previously for the barred sample: Type I profiles are single unbroken exponential radial declines in brightness; Type II profiles ("truncations") have an inner shallow slope (usually exponential) which changes at a well-defined break radius to a steeper exponential; and Type III profiles ("antitruncations") have an inner exponential that is steeper, giving way to a shallower outer (usually exponential) decline. By combining these profiles with previous studies, we can make the first clear statements about the trends of outer-disk-profile types along the Hubble sequence (including both barred and unbarred galaxies), and their global frequencies.
2753. Outflow in M82 halo
ID:
ivo://CDS.VizieR/J/A+A/293/703
Title:
Outflow in M82 halo
Short Name:
J/A+A/293/703
Date:
21 Oct 2021
Publisher:
CDS
Description:
(no description available)
2754. Outflow of H_2_ gas from NGC3256
ID:
ivo://CDS.VizieR/J/A+A/572/A40
Title:
Outflow of H_2_ gas from NGC3256
Short Name:
J/A+A/572/A40
Date:
21 Oct 2021
Publisher:
CDS
Description:
The nuclei of merging galaxies are often deeply buried in dense layers of gas and dust. In these regions, gas outflows driven by starburst and active galactic nuclear activity are believed to play a crucial role in the evolution of these galaxies. However, to fully understand this process it is essential to resolve the morphology and kinematics of such outflows. Using near-infrared integral-field spectroscopy obtained with SINFONI on the Very Large Telescope, we detect a kpc-scale structure of high-velocity molecular hydrogen (H_2_) gas associated with the deeply buried secondary nucleus of the infrared-luminous merger-galaxy NGC 3256. We show that this structure is most likely the hot component of a molecular outflow, which was recently also detected in the cold molecular gas through CO emission.
2755. Outflows in sodium excess objects
ID:
ivo://CDS.VizieR/J/ApJ/809/91
Title:
Outflows in sodium excess objects
Short Name:
J/ApJ/809/91
Date:
21 Oct 2021
Publisher:
CDS
Description:
Van Dokkum and Conroy (2010Natur.468..940V) revisited the unexpectedly strong NaI lines at 8200{AA} found in some giant elliptical galaxies and interpreted them as evidence for an unusually bottom-heavy initial mass function. Jeong et al. (2013, J/ApJS/208/7) later found a large population of galaxies showing equally extraordinary Na D doublet absorption lines at 5900{AA} (Na D excess objects: NEOs) and showed that their origins can be different for different types of galaxies. While a Na D excess seems to be related to the interstellar medium (ISM) in late-type galaxies, smooth-looking early-type NEOs show little or no dust extinction and hence no compelling signs of ISM contributions. To further test this finding, we measured the Doppler components in the Na D lines. We hypothesized that the ISM would have a better (albeit not definite) chance of showing a blueshift Doppler departure from the bulk of the stellar population due to outflow caused by either star formation or AGN activities. Many of the late-type NEOs clearly show blueshift in their Na D lines, which is consistent with the former interpretation that the Na D excess found in them is related to gas outflow caused by star formation. On the contrary, smooth-looking early-type NEOs do not show any notable Doppler components, which is also consistent with the interpretation of Jeong et al. that the Na D excess in early-type NEOs is likely not related to ISM activities but is purely stellar in origin.
2756. outlier detection algorithm for SDSS galaxies
ID:
ivo://CDS.VizieR/J/MNRAS/465/4530
Title:
outlier detection algorithm for SDSS galaxies
Short Name:
J/MNRAS/465/4530
Date:
21 Oct 2021
Publisher:
CDS
Description:
How can we discover objects we did not know existed within the large data sets that now abound in astronomy? We present an outlier detection algorithm that we developed, based on an unsupervised Random Forest. We test the algorithm on more than two million galaxy spectra from the Sloan Digital Sky Survey and examine the 400 galaxies with the highest outlier score. We find objects which have extreme emission line ratios and abnormally strong absorption lines, objects with unusual continua, including extremely reddened galaxies. We find galaxy-galaxy gravitational lenses, double-peaked emission line galaxies and close galaxy pairs. We find galaxies with high ionization lines, galaxies that host supernovae and galaxies with unusual gas kinematics. Only a fraction of the outliers we find were reported by previous studies that used specific and tailored algorithms to find a single class of unusual objects. Our algorithm is general and detects all of these classes, and many more, regardless of what makes them peculiar. It can be executed on imaging, time series and other spectroscopic data, operates well with thousands of features, is not sensitive to missing values and is easily parallelizable.
2757. Outlying HII regions in HI-selected galaxies
ID:
ivo://CDS.VizieR/J/AJ/139/279
Title:
Outlying HII regions in HI-selected galaxies
Short Name:
J/AJ/139/279
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present results from the first systematic search for outlying HII regions, as part of a sample of 96 emission-line point sources (referred to as ELdots-emission-line dots) derived from the NOAO Survey for Ionization in Neutral Gas Galaxies (SINGG). Our automated ELdot finder searches SINGG narrowband and continuum images for high equivalent width point sources outside the optical radius of the target galaxy (>2xr_25_ in the R band). Follow-up long-slit spectroscopy and deep Galaxy Evolution Explorer (GALEX) images (exposure time >1000s) distinguish outlying HII regions from background galaxies whose strong emission lines ([OIII], H{beta], or [OII]) have been redshifted into the SINGG bandpass.
2758. Overdensities of 0<z<3 COSMOS galaxies
ID:
ivo://CDS.VizieR/J/ApJ/805/121
Title:
Overdensities of 0<z<3 COSMOS galaxies
Short Name:
J/ApJ/805/121
Date:
21 Oct 2021
Publisher:
CDS
Description:
It is well-known that a galaxy's environment has a fundamental influence in shaping its properties. We study the environmental effects on galaxy evolution, with an emphasis on the environment defined as the local number density of galaxies. The density field is estimated with different estimators (weighted adaptive kernel smoothing, 10th and 5th nearest neighbors, Voronoi and Delaunay tessellation) for a K_s_<24 sample of ~190000 galaxies in the COSMOS field at 0.1<z<3.1. The performance of each estimator is evaluated with extensive simulations. We show that overall there is a good agreement between the estimated density fields using different methods over ~2dex in overdensity values. However, our simulations show that adaptive kernel and Voronoi tessellation outperform other methods. Using the Voronoi tessellation method, we assign surface densities to a mass complete sample of quiescent and star-forming galaxies out to z~3. We show that at a fixed stellar mass, the median color of quiescent galaxies does not depend on their host environment out to z~3. We find that the number and stellar mass density of massive (>10^11^M_{sun}_) star-forming galaxies have not significantly changed since z~3, regardless of their environment. However, for massive quiescent systems at lower redshifts (z<~1.3), we find a significant evolution in the number and stellar mass densities in denser environments compared to lower density regions. Our results suggest that the relation between stellar mass and local density is more fundamental than the color-density relation and that environment plays a significant role in quenching star-formation activity in galaxies at z<~1.
2759. Overmassive black holes
ID:
ivo://CDS.VizieR/J/MNRAS/446/2330
Title:
Overmassive black holes
Short Name:
J/MNRAS/446/2330
Date:
21 Oct 2021
Publisher:
CDS
Description:
Semi-analytical models in a {Lambda} cold dark matter cosmology have predicted the presence of outlying, 'overmassive' black holes at the high-mass end of the (black hole mass-galaxy velocity dispersion) M_BH_-{sigma} diagram (which we update here with a sample of 89 galaxies). They are a consequence of having experienced more dry mergers - thought not to increase a galaxy's velocity dispersion - than the 'main-sequence' population. Wet mergers and gas-rich processes, on the other hand, preserve the main correlation. Due to the scouring action of binary supermassive black holes, the extent of these dry mergers (since the last significant wet merger) can be traced by the ratio between the central stellar mass deficit and the black hole mass (M_def,*_/M_BH_). However, in a sample of 23 galaxies with partially depleted cores, including central cluster galaxies, we show that the 'overmassive' black holes are actually hosted by galaxies that appear to have undergone the lowest degree of such merging. In addition, the rotational kinematics of 37 galaxies in the M_BH_-{sigma} diagram reveals that fast and slow rotators are not significantly offset from each other, also contrary to what is expected if these two populations were the product of wet and dry mergers, respectively. The observations are thus not in accordance with model predictions and further investigation is required.
2760. Oxygen abundance gradient in M81
ID:
ivo://CDS.VizieR/J/MNRAS/455/2627
Title:
Oxygen abundance gradient in M81
Short Name:
J/MNRAS/455/2627
Date:
21 Oct 2021
Publisher:
CDS
Description:
We study the sensitivity of the methods available for abundance determinations in HII regions to potential observational problems. We compare the dispersions they introduce around the oxygen and nitrogen abundance gradients when applied to five different sets of spectra of HII regions in the galaxy M81. Our sample contains 116 HII regions with galactocentric distances of 3 to 33kpc, including 48 regions observed by us with the OSIRIS long-slit spectrograph at the 10.4-m Gran Telescopio Canarias telescope. The direct method can be applied to 31 regions, where we can get estimates of the electron temperature. The different methods imply oxygen abundance gradients with slopes of -0.010 to -0.002dex/kpc, and dispersions in the range 0.06-0.25dex. The direct method produces the shallowest slope and the largest dispersion, illustrating the difficulty of obtaining good estimates of the electron temperature. Three of the strong-line methods, C, ONS, and N2, are remarkably robust, with dispersions of ~0.06dex, and slopes in the range -0.008 to -0.006dex/kpc. The robustness of each method can be directly related to its sensitivity to the line intensity ratios that are more difficult to measure properly. Since the results of the N2 method depend strongly on the N/O abundance ratio and on the ionization parameter, we recommend the use of the C and ONS methods when no temperature estimates are available or when they have poor quality, although the behaviour of these methods when confronted with regions that have different properties and different values of N/O should be explored.

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