Abstract
We present James Webb Space Telescope (JWST) Near Infrared Spectrograph (NIRSpec) integral field spectroscopy of the nearby luminous infrared galaxy NGC 7469. We take advantage of the high ...spatial/spectral resolution and wavelength coverage of JWST/NIRSpec to study the 3.3
μ
m neutral polycyclic aromatic hydrocarbon (PAH) grain emission on ∼200 pc scales. A clear change in the average grain properties between the star-forming ring and the central AGN is found. Regions in the vicinity of the AGN, with Ne
iii
/Ne
ii
> 0.25, tend to have larger grain sizes and lower aliphatic-to-aromatic (3.4/3.3) ratios, indicating that smaller grains are preferentially removed by photodestruction in the vicinity of the AGN. PAH emission at the nucleus is weak and shows a low 11.3/3.3 PAH ratio. We find an overall suppression of the total PAH emission relative to the ionized gas in the central 1 kpc region of the AGN in NGC 7469 compared to what has been observed with Spitzer on 3 kpc scales. However, the fractional 3.3
μ
m–to–total PAH power is enhanced in the starburst ring, possibly due to a variety of physical effects on subkiloparsec scales, including recurrent fluorescence of small grains or multiple photon absorption by large grains. Finally, the IFU data show that while the 3.3
μ
m PAH-derived star formation rate (SFR) in the ring is 27% higher than that inferred from the Ne
ii
and Ne
iii
emission lines, the integrated SFR derived from the 3.3
μ
m feature would be underestimated by a factor of 2 due to the deficit of PAHs around the AGN, as might occur if a composite system like NGC 7469 were to be observed at high redshift.
We present the first detailed integral field spectroscopy study of nine central void galaxies with M⋆ > 1010 M⊙ using the Wide Field Spectrograph to determine how a range of assembly histories ...manifest themselves in the current day Universe. While the majority of these galaxies are evolving secularly, we find a range of morphologies, merger histories and stellar population distributions, though similarly low Hα-derived star formation rates (<1 M⊙ yr−1). Two of our nine galaxies host active galactic nuclei, and two have kinematic disruptions to their gas that are not seen in their stellar component. Most massive void galaxies are red and discy, which we attribute to a lack of major mergers. Some have disturbed morphologies and may be in the process of evolving to early-type thanks to ongoing minor mergers at present times, likely fed by tendrils leading off filaments. The diversity in our small galaxy sample, despite being of similar mass and environment means that these galaxies are still assembling at present day, with minor mergers playing an important role in their evolution. We compare our sample to a mass and magnitude-matched sample of field galaxies, using data from the Sydney-AAO Multi-object Integral field spectrograph galaxy survey. We find that despite environmental differences, galaxies of mass M⋆ > 1010 M⊙ have similarly low star formation rates (<3 M⊙ yr−1). The lack of distinction between the star formation rates of the void and field environments points to quenching of massive galaxies being a largely mass-related effect.
Abstract
In galaxy clusters, efficiently accreting active galactic nuclei (AGNs) are preferentially located in the infall regions of the cluster projected phase-space, and are rarely found in the ...cluster core. This has been attributed to both an increase in triggering opportunities for infalling galaxies, and a reduction of those mechanisms in the hot, virialized, cluster core. Exploiting the depth and completeness (98 per cent at r < 19.8 mag) of the Galaxy And Mass Assembly survey (GAMA), we probe down the group halo mass function to assess whether AGNs are found in the same regions in groups as they are in clusters. We select 451 optical AGNs from 7498 galaxies with log10(M*/M⊙) > 9.9 in 695 groups with 11.53 ≤ log10(M200/M⊙) ≤ 14.56 at z < 0.15. By analysing the projected phase-space positions of these galaxies, we demonstrate that when split both radially, and into physically derived infalling and core populations, AGN position within group projected phase-space is dependent on halo mass. For groups with log10(M200/M⊙) > 13.5, AGNs are preferentially found in the infalling galaxy population with 3.6σ confidence. At lower halo masses, we observe no difference in AGN fraction between core and infalling galaxies. These observations support a model where a reduced number of low-speed interactions, ram pressure stripping and intra-group/cluster medium temperature, the dominance of which increase with halo mass, work to inhibit AGN in the cores of groups and clusters with log10(M200/M⊙) > 13.5, but do not significantly affect nuclear activity in cores of less massive structures.
We have determined K-band luminosity functions for 13,325 local universe galaxies as a function of morphology and color (for K sub(tot) < or =, slant 10.75). Our sample is drawn from the Two Micron ...All Sky Survey Extended Source Catalog, with all sample galaxies having measured morphologies and distances (including 4219 archival redshift-independent distances). The luminosity function for our total sample is in good agreement with previous works, but is relatively smooth at faint magnitudes (due to bulk flow distance corrections). We investigated the differences due to morphological and color selection using 5417 sample galaxies with NASA Sloan Atlas optical colors and find that red spirals comprise 20%-50% of all spirals with -25 < or =, slant MK < -20. Fainter than MK = -24, red spirals are as common as early types, explaining the different faint end slopes ( alpha = -0.87 and -1.00 for red and early-types, respectively). While we find red spirals comprise more than 50% of all MK < -25 spiral galaxies, they do not dominate the bright end of the overall red galaxy luminosity function, which is dominated by early-type galaxies. The brightest red spirals have ongoing star formation and those without are frequently misclassified as early-types. The faintest ones have an appearance and Sersic indices consistent with faded disks, rather than true bulge-dominated galaxies.
Abstract We present new JWST NIRSpec integral field spectroscopy (IFS) data for the luminous infrared galaxy NGC 7469, a nearby (70.6 Mpc) active galaxy with a Seyfert 1.5 nucleus that drives a ...highly ionized gas outflow and a prominent nuclear star-forming ring. Using the superb sensitivity and high spatial resolution of the JWST instrument NIRSpec IFS, we investigate the role of the Seyfert nucleus in the excitation and dynamics of the circumnuclear gas. Our analysis focuses on the Fe ii , H 2 , and hydrogen recombination lines that trace the radiation/shocked-excited molecular and ionized interstellar medium around the active galactic nucleus (AGN). We investigate gas excitation through H 2 /Br γ and Fe ii /Pa β emission line ratios and find that photoionization by the AGN dominates within the central 300 pc of the galaxy except in a small region that shows signatures of shock-heated gas; these shock-heated regions are likely associated with a compact radio jet. In addition, the velocity field and velocity dispersion maps reveal complex gas kinematics. Rotation is the dominant feature, but we also identify noncircular motions consistent with gas inflows as traced by the velocity residuals and the spiral pattern in the Pa α velocity dispersion map. The inflow is 2 orders of magnitude higher than the AGN accretion rate. The compact nuclear radio jet has enough power to drive the highly ionized outflow. This scenario suggests that the inflow and outflow are in a self-regulating feeding–feedback process, with a contribution from the radio jet helping to drive the outflow.
We describe an accurate new method for determining absolute magnitudes, and hence also K-corrections, that is simpler than most previous methods, being based on a quadratic function of just one ...suitably chosen observed color. The method relies on the extensive and accurate new set of 129 empirical galaxy template spectral energy distributions from Brown et al. A key advantage of our method is that we can reliably estimate random errors in computed absolute magnitudes due to galaxy diversity, photometric error and redshift error. We derive K-corrections for the five Sloan Digital Sky Survey filters and provide parameter tables for use by the astronomical community. Using the New York Value-Added Galaxy Catalog, we compare our K-corrections with those from kcorrect. Our K-corrections produce absolute magnitudes that are generally in good agreement with kcorrect. Absolute griz magnitudes differ by less than 0.02 mag and those in the u band by ~0.04 mag. The evolution of rest-frame colors as a function of redshift is better behaved using our method, with relatively few galaxies being assigned anomalously red colors and a tight red sequence being observed across the whole 0.0 < z < 0.5 redshift range.
We explore the connection between different classes of active galactic nuclei (AGNs) and the evolution of their host galaxies, by deriving host galaxy properties, clustering, and Eddington ratios of ...AGNs selected in the radio, X-ray, and infrared (IR) wavebands. We study a sample of 585 AGNs at 0.25 < z < 0.8 using redshifts from the AGN and Galaxy Evolution Survey (AGES). We select AGNs with observations in the radio at 1.4 GHz from the Westerbork Synthesis Radio Telescope, X-rays from the Chandra XBootes Survey, and mid-IR from the Spitzer IRAC Shallow Survey. The radio, X-ray, and IR AGN samples show only modest overlap, indicating that to the flux limits of the survey, they represent largely distinct classes of AGNs. We derive host galaxy colors and luminosities, as well as Eddington ratios, for obscured or optically faint AGNs. We also measure the two-point cross-correlation between AGNs and galaxies on scales of 0.3-10 h -1 Mpc, and derive typical dark matter halo masses. We find that: (1) radio AGNs are mainly found in luminous red sequence galaxies, are strongly clustered (with M halo ~ 3 X 1013 h -1 M ), and have very low Eddington ratios l 10-3; (2) X-ray-selected AGNs are preferentially found in galaxies that lie in the 'green valley' of color-magnitude space and are clustered similar to the typical AGES galaxies (M halo ~ 1013 h -1 M ), with 10-3 l 1; (3) IR AGNs reside in slightly bluer, slightly less luminous galaxies than X-ray AGNs, are weakly clustered (M halo 1012 h -1 M ), and have l>10-2. We interpret these results in terms of a simple model of AGN and galaxy evolution, whereby a 'quasar' phase and the growth of the stellar bulge occurs when a galaxy's dark matter halo reaches a critical mass between ~1012 and 1013 M . After this event, star formation ceases and AGN accretion shifts from radiatively efficient (optical- and IR-bright) to radiatively inefficient (optically faint, radio-bright) modes.
We present deep Hubble Space Telescope (HST)/Wide-Field Planetary Camera 2 (WFPC2), rest-frame U images of 17 ∼L
quasars at z 1 and 2 (V and I bands, respectively), designed to explore the host ...galaxies. We fit the images with simple axisymmetric galaxy models, including a point source, in order to separate nuclear and host-galaxy emission. We successfully model all of the host galaxies, with luminosities stable to within 0.3 mag. Combining with our earlier Near Infrared Camera and Multi-Object Spectrometer rest-frame optical study of the same sample, we provide the first rest-frame U − V colours for a sample of quasar host galaxies. While the optical luminosities of their host galaxies indicate that they are drawn purely from the most massive ( L
) early-type galaxy population, their colours are systematically bluer than those of comparably massive galaxies at the same redshift. The host galaxies of the radio-loud quasars (RLQs) in our sample are more luminous than their radio-quiet quasar (RQQ) counterparts at each epoch, but have indistinguishable colours, confirming that the RLQs are drawn from only the most massive galaxies (1011-1012 M even at z 2), while the RQQs are slightly less massive (∼1011 M). This is consistent with the well-known anticorrelation between radio-loudness and accretion rate. Using simple stellar population 'frosting' models, we estimate mean star formation rates of ∼350 M yr−1 for the RLQs and ∼100 M yr−1 for the RQQs at z 2. By z 1, these rates have fallen to ∼150 M yr−1 for the RLQs and ∼50 M yr−1 for the RQQs. We conclude that while the host galaxies are extremely massive, they remain actively star forming at, or close to, the epoch of the quasar.
Abstract
We present the results of a James Webb Space Telescope NIRCam investigation into the young massive star cluster (YMC) population in the luminous infrared galaxy VV 114. We identify 374 ...compact YMC candidates with signal-to-noise ratios ≥ 3, 5, and 5 at F150W, F200W, and F356W, respectively. A direct comparison with our HST cluster catalog reveals that ∼20% of these sources are undetected at optical wavelengths. Based on
yggdrasil
stellar population models, we identify 17 YMC candidates in our JWST imaging alone with F150W – F200W and F200W – F356W colors suggesting they are all very young, dusty (
A
V
= 5–15), and massive (10
5.8
<
M
⊙
< 10
6.1
). The discovery of these “hidden” sources, many of which are found in the “overlap” region between the two nuclei, quadruples the number of
t
< 3 Myr clusters and nearly doubles the number of
t
< 6 Myr clusters detected in VV 114. Now extending the cluster age distribution (
dN
/
d
τ
∝
τ
γ
) to the youngest ages, we find a slope of
γ
= −1.30 ± 0.39 for 10
6
<
τ
(yr) < 10
7
, which is consistent with the previously determined value from 10
7
<
τ
(yr) < 10
8.5
, and confirms that VV 114 has a steep age distribution slope for all massive star clusters across the entire range of cluster ages observed. Finally, the consistency between our JWST- and HST-derived age distribution slopes indicates that the balance between cluster formation and destruction has not been significantly altered in VV 114 over the last 0.5 Gyr.
Abstract
We present James Webb Space Telescope (JWST) imaging of NGC 7469 with the Near-Infrared Camera and the Mid-InfraRed Instrument. NGC 7469 is a nearby,
z
= 0.01627, luminous infrared galaxy ...that hosts both a Seyfert Type-1.5 nucleus and a circumnuclear starburst ring with a radius of ∼0.5 kpc. The new near-infrared (NIR) JWST imaging reveals 66 star-forming regions, 37 of which were not detected by Hubble Space Telescope (HST) observations. Twenty-eight of the 37 sources have very red NIR colors that indicate obscurations up to
A
v
∼ 7 and a contribution of at least 25% from hot dust emission to the 4.4
μ
m band. Their NIR colors are also consistent with young (<5 Myr) stellar populations and more than half of them are coincident with the mid-infrared (MIR) emission peaks. These younger, dusty star-forming regions account for ∼6% and ∼17% of the total 1.5 and 4.4
μ
m luminosity of the starburst ring, respectively. Thanks to JWST, we find a significant number of young dusty sources that were previously unseen due to dust extinction. The newly identified 28 young sources are a significant increase compared to the number of HST-detected young sources (4–5). This makes the total percentage of the young population rise from ∼15% to 48%. These results illustrate the effectiveness of JWST in identifying and characterizing previously hidden star formation in the densest star-forming environments around active galactic nuclei (AGN).
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