Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userThe first 62 AGN observed with SDSS-IV MaNGA - I: their characterization and definition of a control sample
56
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We report the characterization of the first $62$ MaNGA Active Galactic Nuclei (AGN) hosts in the Fifth Product Launch (MPL-5) and the definition of a control sample of non-active galaxies. This control sample - comprising two galaxies for each AGN - was selected in order to match the AGN hosts in terms of stellar mass, redshift, visual morphology and inclination. The stellar masses are in the range $9.4<log(M/M_odot)<11.5$, and most objects have redshifts $leq 0.08$. The AGN sample is mostly comprised of low-luminosity AGN, with only 17 nuclei with $L([OIII]lambda 5007)geq 3.8times 10^{40}$ erg s$^{-1}$ (that we call strong AGN). The stellar population of the control sample galaxies within the inner $1$-$3$ kpc is dominated by the old ($sim$ $4$ - $13$ Gyr) age component, with a small contribution of intermediate age ($sim 640$-$940$ Myr) and young stars ($leq 40$ Myr) to the total light at $5700AA$. While the weaker AGN show a similar age distribution to that of the control galaxies, the strong AGN show an increased contribution of younger stars and a decreased contribution of older stars. Examining the relationship between the AGN stellar population properties and $L([OIII])$, we find that with increasing $L([OIII])$, the AGN exhibit a decreasing contribution from the oldest ($>4$ Gyr) stellar population relative to control galaxies, but have an increasing contribution from the younger components with ages $sim 40$ Myr. We also find a correlation of the mean age differences (AGN - control) with $L([OIII])$, in the sense that more luminous AGN are younger than the control objects, while the low-luminosity AGN seem to be older. These results support a connection between the growth of the galaxy bulge via formation of new stars and the growth of the Supermassive Black Hole via matter accretion in the AGN phase.
rate research
Read More
We investigate the effects of Active Galactic Nuclei (AGN) on the gas kinematics of their host galaxies, using MaNGA data for a sample of 62 AGN hosts and 109 control galaxies (inactive galaxies). We compare orientation of the line of nodes (kinematic Position Angle - PA) measured from the gas and stellar velocity fields for the two samples. We found that AGN hosts and control galaxies display similar kinematic PA offsets between gas and stars. However, we note that AGN have larger fractional velocity dispersion $sigma$ differences between gas and stars [$sigma_{frac}=(sigma_{rm gas}-sigma_{stars})/sigma_{rm stars}$] when compared to their controls, as obtained from the velocity dispersion values of the central (nuclear) pixel (2.5 diameter). The AGN have a median value of $sigma_{rm frac}$ of $<sigma_{frac}>_{rm AGN}=0.04$, while the the median value for the control galaxies is $<sigma_{frac}>_{rm CTR}=-0.23$. 75% of the AGN show $sigma_{frac}>-0.13$, while 75% of the normal galaxies show $sigma_{rm frac}<-0.04$, thus we suggest that the parameter $sigma_{rm frac}$ can be used as an indicative of AGN activity. We find a correlation between the [OIII]$lambda$5007 luminosity and $sigma_{frac}$ for our sample. Our main conclusion is that the AGN already observed with MaNGA are not powerful enough to produce important outflows at galactic scales, but at 1-2 kpc scales, AGN feedback signatures are always present on their host galaxies.
Wolf-Rayet (WR) galaxies are a rare population of galaxies that host living high-mass stars during their WR phase (i.e. WR stars) and are thus expected to provide interesting constraints on the stellar Initial Mass Function, massive star formation, stellar evolution models, etc. Spatially resolved spectroscopy should in principle provide a more efficient way of identifying WR galaxies than single-fiber surveys of galactic centers such as SDSS-I & II, as WR stars should be more preferentially found in discs. Using IFU data from the ongoing SDSS-IV MaNGA survey, we have performed a thorough search for WR galaxies. We first identify H II regions in each datacube and carry out full spectral fitting to the stacked spectra. We then visually inspect the residual spectrum of each H II region and identify WR regions that present a significant blue bump at 4600-4750 A. The resulting WR catalog includes 267 WR regions of ~500pc (radius) sizes, distributed in 90 galaxies from the current sample of MaNGA (MaNGA Product Launch 7). We find WR regions are exclusively found in galaxies that show bluest colors and highest star formation rates for their mass. Most WR galaxies have late-type morphologies and show relatively large asymmetry in their images, implying that WR regions are more preferentially found in interacting/merging galaxies. We estimate the stellar mass function of WR galaxies and the mass-dependent detection rate. The detection rate of WR galaxies is typically ~2%, with weak dependence on stellar mass. This detection rate is about 40 times higher than previous studies with SDSS single fiber data, and by a factor of 2 lower than the CALIFA-based WR catalog. We make comparisons with SDSS and CALIFA studies, and conclude that different detection rates can be explained mainly by three factors: spatial coverage, spectral signal-to-noise ratio, and redshift ranges of the parent sample.
We describe the sample design for the SDSS-IV MaNGA survey and present the final properties of the main samples along with important considerations for using these samples for science. Our target selection criteria were developed while simultaneously optimizing the size distribution of the MaNGA integral field units (IFUs), the IFU allocation strategy, and the target density to produce a survey defined in terms of maximizing S/N, spatial resolution, and sample size. Our selection strategy makes use of redshift limits that only depend on i-band absolute magnitude ($M_i$), or, for a small subset of our sample, $M_i$ and color (NUV-i). Such a strategy ensures that all galaxies span the same range in angular size irrespective of luminosity and are therefore covered evenly by the adopted range of IFU sizes. We define three samples: the Primary and Secondary samples are selected to have a flat number density with respect to $M_i$ and are targeted to have spectroscopic coverage to 1.5 and 2.5 effective radii (Re), respectively. The Color-Enhanced supplement increases the number of galaxies in the low-density regions of color-magnitude space by extending the redshift limits of the Primary sample in the appropriate color bins. The samples cover the stellar mass range $5times10^8 leq M_* leq 3times10^{11} M_{odot}$ and are sampled at median physical resolutions of 1.37 kpc and 2.5 kpc for the Primary and Secondary samples respectively. We provide weights that will statistically correct for our luminosity and color-dependent selection function and IFU allocation strategy, thus correcting the observed sample to a volume limited sample.
Using kinematic maps from the Sloan Digital Sky Survey (SDSS) Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey, we reveal that the majority of low-mass quenched galaxies exhibit coherent rotation in their stellar kinematics. Our sample includes all 39 quenched low-mass galaxies observed in the first year of MaNGA. The galaxies are selected with $M_{r} > -19.1$, stellar masses $10^{9}$ M$_{odot} < M_{star} < 5times10^{9}$ M$_{odot}$, EW$_{Halpha} <2$ AA, and all have red colours $(u-r)>1.9$. They lie on the size-magnitude and $sigma$-luminosity relations for previously studied dwarf galaxies. Just six ($15pm5.7$ per cent) are found to have rotation speeds $v_{e,rot} < 15$ km s$^{-1}$ at $sim1$ $R_{e}$, and may be dominated by pressure support at all radii. Two galaxies in our sample have kinematically distinct cores in their stellar component, likely the result of accretion. Six contain ionised gas despite not hosting ongoing star formation, and this gas is typically kinematically misaligned from their stellar component. This is the first large-scale Integral Field Unit (IFU) study of low mass galaxies selected without bias against low-density environments. Nevertheless, we find the majority of these galaxies are within $sim1.5$ Mpc of a bright neighbour ($M_{K} < -23$; or M$_{star} > 5times10^{10}$ M$_{odot}$), supporting the hypothesis that galaxy-galaxy or galaxy-group interactions quench star formation in low-mass galaxies. The local bright galaxy density for our sample is $rho_{proj} = 8.2pm2.0$ Mpc$^{-2}$, compared to $rho_{proj} = 2.1pm0.4$ Mpc$^{-2}$ for a star forming comparison sample, confirming that the quenched low mass galaxies are preferentially found in higher density environments.
Estimating the bar pattern speed (Om{}) is one of the main challenges faced in understanding the role of stellar bars in galaxy dynamical evolution. This work aims to characterise different uncertainty sources affecting the Tremaine Weinberg (TW)-method to study the correlation between bar and galaxies physical parameters. We use a sample of 15 MaNGA SDSS-IV galaxies and 3 CALIFA galaxies from cite{Aguerri2015}. We studied the errors related with (i) galaxy centre determination, (ii) disc position angle (PA) emphasising the difficulties triggered by outer non-axisymmetric structures besides the bar, (iii) the slits length and (iv) the spatial resolution. In average, the PA uncertainties range $sim 15 %$, the slit length $sim 9 %$ and the centring error $sim 5 %$. Reducing the spatial resolution increases the sensitivity to the PA error. Through Monte Carlo simulations, we estimate the probability distribution of the R{} bar speed parameter. The present sample is composed of 7 slow, 4 fast and 7 ultrafast bars, with no trend with morphological types. Although uncertainties and low sample numbers may mask potential correlations between physical properties, we present a discussion of them: We observe an anti-correlation of Om{} with the bar length and the stellar mass, suggesting that massive galaxies tend to host longer and slower bars. We also observe a correlation of the molecular gas fraction with R{}, and a weak anti-correlation with Om{}, suggesting that bars rotate slower in gaseous discs. Confirmation of such trends awaits future studies.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
