We obtained a 5 ks deep Chandra X-ray Observatory ACIS-I map of the 9.3 deg super(2) Bootes field of the NOAO Deep Wide-Field Survey. Here we describe the data acquisition and analysis strategies ...leading to a catalog of 4642 (3293) point sources with 2 or more (4 or more) counts, corresponding to a limiting flux of roughly 4(8) x 10 super(-15) ergs cm super(-2) s super(-1) in the 0.5-7 keV band. These Chandra XBootes data are unique in that they constitute the widest contiguous X-ray field yet observed to such a faint flux limit. Because of the extraordinarily low background of the ACIS, we expect only 14% (0.7%) of the sources to be spurious. We also detected 43 extended sources in this survey. The distribution of the point sources among the 126 pointings (ACIS-I has a 16' x 16' field of view) is consistent with Poisson fluctuations about the mean of 36.8 sources per pointing. While a smoothed image of the point source distribution is clumpy, there is no statistically significant evidence of large-scale filamentary structure. We do find however, that for f > 1', the angular correlation function of these sources is consistent with previous measurements, following a power law in angle with slope 6-0.7. In a 1.4 deg super(2) sample of the survey, approximately 87% of the sources with 4 or more counts have an optical counterpart to R 6 26 mag. As part of a larger program of optical spectroscopy of the NDWFS Bootes area, spectra have been obtained for 6900 of the X-ray sources, most of which are quasars or active galactic nuclei.
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.
We have calibrated the 6.5 m James Webb Space Telescope (JWST) mid-infrared (MIR) filters as star formation rate (SFR) indicators, using JWST photometry synthesized from Spitzer spectra of 49 ...low-redshift galaxies, which cover a wider luminosity range than most previous studies. We use Balmer-decrement-corrected H luminosity and synthesized MIR photometry to empirically calibrate the Spitzer, WISE, and JWST filters as SFR indicators. Our Spitzer and WISE calibrations are in good agreement with recent calibrations from the literature. While MIR luminosity may be directly proportional to SFR for high-luminosity galaxies, we find a power-law relationship between MIR luminosity and SFR for low-luminosity galaxies ( ). We find that for galaxies with an H luminosity of (corresponding to an SFR of ), the corresponding JWST MIR L luminosity is between 1040.50 and . Power-law fits of JWST luminosity as a function of H luminosity have indices between 1.17 and 1.32. We find that the scatter in the JWST filter calibrations decreases with increasing wavelength from 0.39 to 0.20 dex, although F1000W is an exception where the scatter is just 0.24 dex.
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).
The formation and evolution of massive red galaxies form a crucial test of theories of galaxy formation based on hierarchical assembly. In this Letter we use observations of the clustering of ...luminous red galaxies from the Booetes field and N-body simulations to argue that about of the most luminous satellite galaxies appear to undergo merging or disruption within massive halos between z 0.9 and 0.5.
We investigate the average physical properties and star formation histories (SFHs) of the most UV-luminous star-forming galaxies at z ~ 3.7. Our results are based on the average spectral energy ...distributions (SEDs), constructed from stacked optical-to-infrared photometry, of a sample of the 1913 most UV-luminous star-forming galaxies found in 5.3 deg2 of the NOAO Deep Wide-Field Survey. We find that the shape of the average SED in the rest optical and infrared is fairly constant with UV luminosity, i.e., more UV-luminous galaxies are, on average, also more luminous at longer wavelengths. In the rest UV, however, the spectral slope Delta *b (= dlogF Delta *l/dlog Delta *l; measured at 0.13 Delta *mm < Delta *lrest < 0.28 Delta *mm) rises steeply with the median UV luminosity from --1.8 at L L* to --1.2 (L 4-5L*). We use population synthesis analyses to derive their average physical properties and find that (1) L UV and thus star formation rates (SFRs) scale closely with stellar mass such that more UV-luminous galaxies are also more massive, (2) the median ages indicate that the stellar populations are relatively young (200-400 Myr) and show little correlation with UV luminosity, and (3) more UV-luminous galaxies are dustier than their less-luminous counterparts, such that L 4-5L* galaxies are extincted up to A(1600) = 2 mag while L L* galaxies have A(1600) = 0.7-1.5 mag. We argue that the average SFHs of UV-luminous galaxies are better described by models in which SFR increases with time in order to simultaneously reproduce the tight correlation between the UV-derived SFR and stellar mass and their universally young ages. We demonstrate the potential of measurements of the SFR-M * relation at multiple redshifts to discriminate between simple models of SFHs. Finally, we discuss the fate of these UV-brightest galaxies in the next 1-2 Gyr and their possible connection to the most massive galaxies at z ~ 2.
We present results from a Chandra survey of the 9 deg super(2) Bootes field of the NOAO Deep Wide-Field Survey (NDWFS). This XBootes survey consists of 126 separate contiguous ACIS-I observations ...each of approximately 5000 s in duration. These unique Chandra observations allow us to search for large-scale structure and to calculate X-ray source statistics over a wide, contiguous field of view with arcsecond angular resolution and uniform coverage. Optical spectroscopic follow-up observations and the rich NDWFS data set will allow us to identify and classify these X-ray-selected sources. Using wavelet decomposition, we detect 4642 point sources with n . 2 counts. In order to keep our detections 699% reliable, we limit our list to sources with n . 4 counts. For a 5000 s observation and assuming a canonical unabsorbed active galactic nucleus (AGN) type X-ray spectrum, a 4 count on-axis source corresponds to a flux of 4.7 x 10 super(-15) ergs cm super(-2) s super(-1) in the soft (0.5-2 keV) band, 1.5 x 10 super(-14) ergs cm super(-2) s super(-1) in the hard (2-7 keV) band, and 7.8 x 10 super(-15) ergs cm super(-2) s super(-1) in the full (0.5-7 keV) band. The full 0.5-7 keV band n . 4 count list has 3293 point sources. In addition to the point sources, 43 extended sources have been detected, consistent with the depth of these observations and the number counts of clusters. We present here the X-ray catalog for the XBootes survey, including source positions, X-ray fluxes, hardness ratios, and their uncertainties. We calculate and present the differential number of sources per flux density interval, N(S), for the point sources. In the soft (0.5-2 keV) band, N(S) is well fitted by a broken power law with slope of 2.60 sub(-0.12) super(+0.11) at bright fluxes and 1.74 sub(-0.22) super(+0.28) for faint fluxes. The hard source N(S) is well described by a single power law with an index of -2.93 sub(-0.09) super(+0.09).
There exist conflicting observations on whether or not the environment of broad- and narrow-line active galatic nuclei (AGN) differ and this consequently questions the validity of the AGN unification ...model. The high spectroscopic completeness of the Galaxy and Mass Assembly (GAMA) survey makes it ideal for a comprehensive analysis of the close environment of galaxies. To exploit this, and conduct a comparative analysis of the environment of broad- and narrow-line AGN within GAMA, we use a double-Gaussian emission line fitting method to model the more complex line profiles associated with broad-line AGN. We select 209 type 1 (i.e. unobscured), 464 type 1.5-1.9 (partially obscured), and 281 type 2 (obscured) AGN within the GAMA II data base. Comparing the fractions of these with neighbouring galaxies out to a pair separation of 350 kpc h super( -1) and ...z < 0.012 shows no difference between AGN of different type, except at separations less than 20 kpc h super( -1) where our observations suggest an excess of type 2 AGN in close pairs. We analyse the properties of the galaxies neighbouring our AGN and find no significant differences in colour or the star formation activity of these galaxies. Further to this, we find that ... is also consistent between broad- and narrow-line AGN. We conclude that the observations presented here are consistent with AGN unification. (ProQuest: ... denotes formulae/symbols omitted.)
Abstract
We present a sample of 91 H i galaxies with little or no star formation, and discuss the analysis of the integral field unit (IFU) spectra of 28 of these galaxies. We identified H i galaxies ...from the H i Parkes All-Sky Survey Catalog (HICAT) with Wide-field Infrared Survey Explorer (WISE) colours consistent with low specific star formation (<10−10.4 yr−1), and obtained optical IFU spectra with the Wide-Field Spectrograph (WiFeS). Visual inspection of the PanSTARRS, Dark Energy Survey, and Carnegie-Irvine imaging of 62 galaxies reveals that at least 32 galaxies in the sample have low levels of star formation, primarily in arms/rings. New IFU spectra of 28 of these galaxies reveals 3 galaxies with central star formation, 1 galaxy with low-ionization nuclear emission-line regions (LINERs), 20 with extended low-ionization emission-line regions (LIERs), and 4 with high excitation Seyfert (Sy) emission. From the spectroscopic analysis of H i selected galaxies with little star formation, we conclude that 75 per cent of this population are LINERs/LIERs.
The spatial clustering properties of H i galaxies can be studied using the formalism of the halo occupation distribution (HOD). The resulting parameter constraints describe properties like gas ...richness versus environment. Unfortunately, clustering studies based on individual H i galaxies will be restricted to the local Universe for the foreseeable future, even with the deepest H i surveys. Here, we discuss how clustering studies of the H i HOD could be extended to moderate redshift, through observations of fluctuations in the combined 21-cm intensity of unresolved galaxies. In particular, we make an analytic estimate for the clustering of H i in the HOD. Our joint goals are to estimate (i) the amplitude of the signal and (ii) the sensitivity of telescopes like the Australian Square Kilometre Array Pathfinder to HOD parameters. We find that the power spectrum of redshifted 21-cm intensity could be used to study the distribution of H i within dark matter haloes at z > rsim 0.5 where individual galaxies cannot be detected. In addition to the HOD of H i, the amplitude of the 21-cm power spectrum would also yield estimates of the cosmic H i content at epochs between the local Universe and redshifts probed by damped Lyα absorbers.
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