arXiv subjects

Marcia J. Rieke

Publications and source records attributed to Marcia J. Rieke.

71 records · Page 4Linked to original sources

arXiv2003

A Medium-Resolution Near-Infrared Spectral Library of Late Type Stars: I

We present an empirical infrared spectral library of medium resolution (R~2000-3000) H (1.6 micron) and K (2.2 micron) band spectra of 218 red stars, spanning a range of [Fe/H] from ~-2.2 to ~+0.3. The sample includes Galactic disk stars, bulge stars from Baade's window, and red giants from Galactic globular clusters. We report the values of 19 indices covering 12 spectral features measured from the spectra in the library. Finally, we derive calibrations to estimate the effective temperature, and diagnostic relationships to determine the luminosity classes of individual stars from near-infrared spectra. This paper is part of a larger effort aimed at building a near-IR spectral library to be incorporated in population synthesis models, as well as, at testing synthetic stellar spectra.

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arXiv2003

Evolution in the Colors of Lyman-Break Galaxies from Z~4 to Z~3

The integrated colors of distant galaxies provide a means for interpreting the properties of their stellar content. Here, we use rest-frame UV-to-optical colors to constrain the spectral-energy distributions and stellar populations of color-selected, B-dropout galaxies at z ~ 4 in the Great Observatories Origins Deep Survey. We combine the ACS data with ground-based near-infrared images, which extend the coverage of galaxies at z ~ 4 to the rest-frame B-band. We observe a color-magnitude trend in the rest-frame m(UV) - B versus B diagram for the z ~ 4 galaxies that has a fairly well-defined "blue-envelope", and is strikingly similar to that of color-selected, U-dropout galaxies at z ~ 3. We also find that although the co-moving luminosity density at rest-frame UV wavelengths (1600 Angstroms) is roughly comparable at z ~ 3 and z ~ 4, the luminosity density at rest-frame optical wavelengths increases by about one-third from z ~ 4 to z ~ 3. Although the star-formation histories of individual galaxies may involve complex and stochastic events, the evolution in the global luminosity density of the UV-bright galaxy population corresponds to an average star-formation history with a star-formation rate that is constant or increasing over these redshifts. This suggests that the evolution in the luminosity density corresponds to an increase in the stellar-mass density of more than 33%.

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arXiv2002

The [FeII]1.644micron emission in M82 and NGC253: Is it a measure of the supernova rate?

We present HST/NICMOS [FeII]1.644micron, Pa-alpha (1.87micron) and continuum images of the starburst galaxies M82 and NGC253 at an unprecedented spatial resolution. In both galaxies we detect [FeII] compact sources superimposed on a diffuse background in the disk of the galaxies together with a component above and below the plane of the galaxy. The radio and [FeII] emissions perpendicular to the disk of M82 show a remarkable similarity to each other, suggesting that both emissions originate in shocks from supernova explosions. We find a spatial correspondence between bright compact [FeII] emitting regions and the location of radio supernova remnants (SNR) for approximately 30-50% of radio SNRs in M82 and NGC253. This lack of a one-to-one correspondence, more than being indicative of a different origin for the radio and [FeII] emission in starbursts, suggests two populations of SNRs: an older population(<10^4yr) traced by the [FeII] emission and a younger population (a few hundred years old) traced by the radio SNRs. We therefore conclude that the [FeII] emission in starburst galaxies provides a good estimate of the supernova activity. Using our newly determined [FeII] luminosities (corrected for extinction) of M82 and NGC253, we reevaluate the calibration of the supernova rate in terms of the [FeII] luminosity for starburst galaxies.

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arXiv2002

Measuring Distances and Probing the Unresolved Stellar Populations of Galaxies Using Infrared Surface Brightness Fluctuations

To empirically calibrate the IR surface brightness fluctuation (SBF) distance scale and probe the properties of unresolved stellar populations, we measured fluctuations in 65 galaxies using NICMOS on the Hubble Space Telescope. The early-type galaxies in this sample include elliptical and S0 galaxies and spiral bulges in a variety of environments. Absolute fluctuation magnitudes in the F160W (1.6 micron) filter were derived for each galaxy using previously-measured I-band SBF and Cepheid variable star distances. F160W SBFs can be used to measure distances to early-type galaxies with a relative accuracy of ~10% provided that the galaxy color is known to ~0.035 mag or better. Near-IR fluctuations can also reveal the properties of the most luminous stellar populations in galaxies. Comparison of F160W fluctuation magnitudes and optical colors to stellar population model predictions suggests that bluer elliptical and S0 galaxies have significantly younger populations than redder ones, and may also be more metal-rich. There are no galaxies in this sample with fluctuation magnitudes consistent with old, metal-poor (t>5 Gyr, [Fe/H]<-0.7) stellar population models. Composite stellar population models imply that bright fluctuations in the bluer galaxies may be the result of an episode of recent star formation in a fraction of the total mass of a galaxy. Age estimates from the F160W fluctuation magnitudes are consistent with those measured using the H-beta Balmer line index. The two types of measurements make use of completely different techniques and are sensitive to stars in different evolutionary phases. Both techniques reveal the presence of intermediate-age stars in the early-type galaxies of this sample.

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arXiv2002

Hubble Space Telescope NICMOS Imaging of the Core of M87

We present broad-band 1.1, 1.6 and 2.2 micron images and a 2.37 micron narrow-band image of the inner 19" of the nearby radio galaxy M87, obtained with the Near Infrared Camera and Multi-Object Spectrometer of the Hubble Space Telescope (HST). The isophotes of the broad-band images are almost perfectly circular to within approximately 0.5" (~ 50 pc) of the active nucleus, and an r**1/4 law provides a good fit to the galaxy profile to within the same distance. This result agrees with predictions that the nuclear supermassive black hole will produce a nearly spherical distribution of the surrounding stars within a galaxy crossing time. A difference image formed from the 1.6 micron image and a V-band image obtained with the HST Wide Field Planetary Camera 2 does not show any clear evidence of a physically thick dusty torus around the nucleus, consistent with its lack of strong thermal infrared emission. The images and associated colors also confirm that the regions beyond the nucleus do not contain strongly concentrated dust,in contrast to many other radio galaxies. In combination with other recent observations, these results indicate that M87 represents the dynamically evolved product of past galaxy mergers, and suggest that its nucleus is in the final stages of activity.

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arXiv2002

Massive Star Formation in Luminous Infrared Galaxies: Giant HII Regions and their relation to Super Star Clusters

We have used HST/NICMOS H-band narrow-band Pa-alpha (at rest 1.87micron) images to identify star clusters and HII regions respectively in a sample of 8 luminous infrared galaxies (LIRGs). These observations have revealed the presence of a large population of super star clusters (SSC) and bright HII regions. A significant fraction of the HII regions shows H-alpha luminosities above that of 30 Doradus, the prototypical giant HII region. The excess of extremely luminous HII regions in LIRGs has been confirmed by comparison with normal galaxies observed at similar spatial resolutions. Despite the large numbers of identified star clusters and HII regions in LIRGs, we only find a small fraction of coincidences, between 4% and 30%. Using synthesis models we have reproduced the relative fractions of young HII regions, intermediate and old star clusters observed in Arp299 and the central region NGC3256 using a Salpeter IMF and instantaneous star formation. HII regions with no detected near-infrared cluster counterpart (25-39%) represent the youngest sites of star formation, with ages of up to approximately 5Myr and mostly intermediate mass (~10^5Msun) ionizing clusters. For these two galaxies, and within the present detection threshold we can only detect coincidences (4-10%) between an HII region and a near-infrared star cluster for the most massive star clusters (~10^6Msun) during the first 7Myr of their evolution. The identified near-infrared SSCs with no detectable Pa-alpha emission represent the ``old'' population (53-66% of the detected sources), with ages of between 7 and 20-40Myr. Older clusters possibly created in this or previous episodes of star formation are likely to exist in these systems but cannot be identified with the present detection threshold. (Abridged)

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arXiv2001

NICMOS Imaging of the Cores of M 31 and M 32

We present 1.1, 1.6, and 2.2 micron images of the cores of the Local Group galaxies M 31 and M 32 obtained with the Near Infrared Camera and Multi-Object Spectrometer (NICMOS) instrument of the Hubble Space Telescope. These images are also compared to optical images of the galaxies obtained with the HST Wide Field Planetary Camera 2 (WFPC2). In M 31 the nucleus remains distinctly asymmetric in all of the infrared bands, with no evidence of concentrated dust, although the distinction between the two nuclei, P1 and P2, is not as strong as in the WFPC and WFPC2 images. This result is nonetheless consistent with the model of the nucleus as an eccentric stellar disk produced by the dynamical influence of a central supermassive black hole. Several individual M-giant stars are detected within ~ 3" of the nuclei, and may represent stars that have escaped from the disk and phase-mixed around the nuclear center of mass. In M 32 we also do not find strong evidence of dust, and the brightness profiles within the central ~ 1" of the infrared images can be fitted by a power law of the same form as that fitted to the optical images. The infrared color profiles of the central few arcseconds of M 32 show no strong gradients, and indicate a population dominated by K-giant stars. This is consistent with recent groud-based spectroscopy and photometry of the core region, which similarly show no strong gradients in age or metallicity within its stellar population.

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arXiv2000

A Search for the Damped Ly-alpha Absorber at z=1.86 toward QSO 1244+3443 with NICMOS

We have carried out a high-resolution imaging search for the galaxy associated with the damped Lyman-alpha (DLA) absorber at z=1.859 toward the z_{em}=2.48 quasar QSO 1244+3443, using the HST and the NICMOS. Images were obtained in the broad filter F160W and the narrow filter F187N with camera 2 on NICMOS with the goal of detecting the rest-frame optical continuum and the H-alpha line emission from the DLA. After PSF subtraction, two weak features are seen at projected separations of 0.16-0.24" from the quasar. Parts of these features may be associated with the DLA absorber, although we cannot completely rule out that they could be artifacts of the point spread function (PSF). If associated with the DLA, the objects would be ~1-2 h_{70}^{-1} kpc in size with integrated flux densities of 2.5 and 3.3 mu Jy in the F160W filter, implying luminosities at lambda_{central}=5600 A in the DLA rest frame of 4.4-5.9 x 10^{9} h_{70}^{-2} L_{solar} at z=1.86, for q0=0.5. However, no significant H-alpha line emission is seen from these objects, suggesting low star formation rates (SFRs). Our 3 sigma upper limit on the SFR in the DLA is 1.3 h_{70}^{-2} M_{solar}/yr for q0 = 0.5 (2.4 h_{70}^{-2} M_{solar} yr^{-1} for q0 = 0.1). This together with our earlier result for LBQS 1210+1731 mark a significant improvement over previous constraints on the star formation rates of DLAs. A combination of low SFR and some dust extinction is likely to be responsible for the lack of H-alpha emission. Alternatively, the objects, may be associated with the quasar host galaxy. In any case, our observations suggest that the DLA is not a large bright proto-disk, but a compact object or a low-surface brightness galaxy. If the two features are PSF artifacts then the constraints on DLA properties are even more severe.

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arXiv2000

The Infrared Surface Brightness Fluctuation Hubble Constant

We measured infrared surface brightness fluctuation (SBF) distances to an isotropically-distributed sample of 16 distant galaxies with redshifts reaching 10,000 km/s using the near-IR camera and multi-object spectrometer (NICMOS) on the Hubble Space Telescope (HST). The excellent spatial resolution, very low background, and brightness of the IR fluctuations yielded the most distant SBF measurements to date. Twelve nearby galaxies were also observed and used to calibrate the F160W (1.6 micron) SBF distance scale. Of these, three have Cepheid variable star distances measured with HST and eleven have optical I-band SBF distance measurements. A distance modulus of 18.5 mag to the Large Magellanic Cloud was adopted for this calibration. We present the F160W SBF Hubble diagram and find a Hubble constant Ho=76 +/- 1.3 (1-sigma statistical) +/- 6 (systematic) km/s/Mpc. This result is insensitive to the velocity model used to correct for local bulk motions. Restricting the fit to the six most distant galaxies yields the smallest value of Ho=72 +/- 2.3 km/s/Mpc consistent with the data. This 6% decrease in the Hubble constant is consistent with the hypothesis that the Local Group inhabits an under-dense region of the universe, but is also consistent with the best-fit value of Ho=76 km/s/Mpc at the 1.5-sigma level.

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arXiv2000

Testing the AGN-Starburst Connection in Seyfert Galaxies

We use the CO band at 2.3 micron to constrain the populations of young stars in the central regions of Seyfert galaxies. We report new CO band spectroscopy of 46 Seyfert galaxies. In most cases, the observed CO indices appear diluted by the presence of a non-stellar component (most likely, warm dust surrounding the active nucleus). We used JHKL aperture photometry to estimate the non-stellar contribution at 2.3 micron. We successfully corrected the CO band for the dilution for 16 galaxies which were not dominated by the non-stellar component. Comparing with CO indices measured in elliptical and purely starbursting galaxies, we find no evidence for strong starbursts in the majority of these galaxies.

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arXiv2000

A Color Analysis of the NICMOS Parallel Image Archive

We present a photometric analysis of all high Galactic lattitude (|b| > 20d) broad-band parallel images taken by the Near Infrared Camera and Multi-Object Spectrometer (NICMOS) instrument during its initial lifetime in HST Cycle 7. These images, taken through the F110W and F160W filters, reach a mean 3-sigma limiting magnitude of approximately 22 in both bands, and cover a total area of approximately 92 square arcminutes. The reddest of the 358 galaxies detected have F110W-F160W colors and F160W magnitudes consistent with being a combination of both dusty star-forming and evolved early-type galaxies at 1 < z < 2. The surface density of these galaxies is comparable to that of the population of Extremely Red Objects (EROs) discovered in ground-based surveys (~ 100 deg-2), suggesting that EROs also represent a combination of both galaxy types in this redshift range. Roughly 10% of the detected galaxies appear to be blue compact dwarf galaxies at z < 1, a result consistent with studies of the HST Medium Deep Survey Fields. The surface density of these objects down to magnitude of 22 in F160W is ~ 300 deg-2. None of the 681 point sources detected have F110W-F160W colors matching those expected for QSOs whose continua have been significantly reddened by internal dust. Our data limit the surface density of such QSOs to be < 50 deg-2 down the mean limiting magnitudes of the sample images. Since the surface density of QSOs detected on the basis of ultraviolet excess in optical surveys to comparable depth is ~ 100 deg-2, this argues against the suggestion that dust-reddened QSOs comprise the undetected majority of the QSO population. The F110W-F160W color can also be used to identify unreddened QSOs at z > 8, but we find no such candidates. This is consistent with the evidence that QSO space density declines sharply at z > 5.

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arXiv2000

The Initial Mass Function of Low-Mass Stars and Brown Dwarfs in Young Clusters

We have obtained images of the Trapezium Cluster (140" x 140"; 0.3 pc x 0.3 pc) with the Hubble Space Telescope Near-Infrared Camera and Multi-Object Spectrometer (NICMOS). Combining these data with new ground-based K-band spectra (R=800) and existing spectral types and photometry and the models of D'Antona & Mazzitelli, we find that the distributions of ages of comparable samples of stars in the Trapezium, rho Oph, and IC 348 indicate median ages of \~0.4 Myr for the first two regions and ~1-2 Myr for the latter. The low-mass IMFs in these sites of clustered star formation are similar over a wide range of stellar densities and other environmental conditions. With current data, we cannot rule out modest variations in the substellar mass functions among these clusters. We then make the best estimate of the true form of the IMF in the Trapezium by using the evolutionary models of Baraffe et al. and an empirically adjusted temperature scale and compare this mass function to recent results for the Pleiades and the field. All of these data are consistent with an IMF that is flat or rises slowly from the substellar regime to about 0.6 Msun, and then rolls over into a power law that continues from about 1 Msun to higher masses with a slope similar to or somewhat larger than the Salpeter value of 1.35. For the Trapezium, this behavior holds from our completeness limit of ~0.02 Msun and probably, after a modest completeness correction, even from 0.01-0.02 Msun. These data include ~50 likely brown dwarfs. We test the predictions of theories of the IMF against various properties of the observed IMF.

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arXiv2000

NICMOS Imaging of a Damped Lyman-alpha Absorber at z=1.89 toward LBQS 1210+1731 : Constraints on Size and Star Formation Rate

We report results of a high-resolution imaging search (in rest frame H-$α$ and optical continuum) for the galaxy associated with the damped Lyman-$α$ (DLA) absorber at $z=1.892$ toward the $z_{em}=2.543$ quasar LBQS 1210+1731, using HST/NICMOS. After PSF subtraction, a feature is seen in both the broad-band and narrow-band images, at a projected separation of 0.25$\arcsec$ from the quasar. If associated with the DLA, the object would be $\approx 2-3$ $h_{70}^{-1}$ kpc in size with a flux of $9.8 \pm 2.4$ $μ$Jy in the F160W filter, implying a luminosity at $λ_{central}=5500$ Å in the rest frame of $1.5 \times 10^{10}$ $h_{70}^{-2}$ L$_{\odot}$ at $z=1.89$, for $q_{0}=0.5$. However, no significant H-$α$ emission is seen, suggesting a low star formation rate (SFR) (3 $σ$ upper limit of 4.0 $h_{70}^{-2}$ M$_{\odot}$ yr$^{-1}$), or very high dust obscuration. Alternatively, the object may be associated with the host galaxy of the quasar. H-band images obtained with the NICMOS camera 2 coronagraph show a much fainter structure $\approx 4-5$ $h_{70}^{-1}$ kpc in size and containing four knots of continuum emission, located 0.7$\arcsec$ away from the quasar. We have probed regions far closer to the quasar sight-line than in most previous studies of high-redshift intervening DLAs. The two objects we report mark the closest detected high-redshift DLA candidates yet to any quasar sight line. If the features in our images are associated with the DLA, they suggest faint, compact, somewhat clumpy objects rather than large, well-formed proto-galactic disks or spheroids.

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arXiv1999

The Nature of LINERs

We present $J$-band ($1.15-1.35 μ$m) spectroscopy of a sample of nine galaxies showing some degree of LINER activity (classical LINERs, weak-[O {\sc i}] LINERs and transition objects), together with $H$-band spectroscopy for some of them. A careful subtraction of the stellar continuum allows us to obtain reliable [Fe {\sc ii}]$1.2567 μ$m/Pa$β$ line ratios. We conclude that different types of LINERs (i.e., photoionized by a stellar continuum or by an AGN) cannot be easily distinguished based solely on the [Fe {\sc ii}]$1.2567 μ$m/Pa$β$ line ratio. The emission line properties of many LINERs can be explained in terms of an aging starburst. The optical line ratios of these LINERs are reproduced by a model with a metal-rich H {\sc ii} region component photoionized with a single stellar temperature $T_* = 38,000 $K, plus a supernova remnant (SNR) component. The [Fe {\sc ii}] line is predominantly excited by shocks produced by SNRs in starbursts and starburst-dominated LINERs, while Pa$β$ tracks H {\sc ii} regions ionized by massive young stars. The contribution from SNRs to the overall emission line spectrum is constrained by the [Fe {\sc ii}]$1.2567 μ$m/Pa$β$ line ratio. Although our models for aging starbursts are constrained only by these infrared lines, they consistently explain the optical spectra of the galaxies also. The LINER-starburst connection is tested by predicting the time dependence of the ratio of the ionizing luminosity ($L_{\rm ion}$) to the supernova rate (SNr), $L_{\rm ion}$/(SNr). We predict the relative number of starbursts to starburst-dominated LINERs (aging starbursts) and show that it is in approximate agreement with survey findings for nearby galaxies.

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arXiv1999

An Infrared Determination of the Reddening and Distance to Dwingeloo 1

We present for the first time infrared observations of the nearby highly obscured galaxy Dwingeloo 1 (Dw1), including deep H-band imaging covering a total of 4.9x4.9 arcmin, together with J and Ks imaging of the central 2.5x2.5 arcmin. We used the small dispersion of the intrinsic infrared colors of spiral galaxies to determine an infrared H-band extinction of A_H = 0.47+/-0.11 mag towards Dw1. In using infrared colors, the uncertainties in the reddening and distance are reduced by a factor of three. The H-band magnitude corrected for extinction and the infrared Tully-Fisher relation are then used to estimate a distance modulus of (m-M)_0 = 28.62+/-0.27, and thus a distance of d = 5.3 {+0.7/-0.6} Mpc, which puts Dw1 at the far end of the IC342/Maffei 1 & 2 group. Our result is largely independent of the nature of the reddening law because we estimated both the reddening and the distance at the same wavelength range.

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arXiv1998

NICMOS Observations of the Hubble Deep Field: Observations, Data Reduction, and Galaxy Photometry

This paper contains a catlog of sources observed in a portion of the Hubble Deep Field by the NICMOS instrument. Methods of observation and data analysis are discussed. The catalog has two parts. The first is a listing of all sources with signal to noise ratios greater than or equal to 2.5. The second part contains sources with signal to noise ratios less than 2.5. The second part is intended for researchers who wish to know the limits to which sources may appear at a location.

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arXiv1993

M51 Stripped To Its Bones

We present optical and IR surface photometry of M51 (NGC~5194) at B~V~R~I~J~K and CO$(2.3μ)$. These data are used to establish whether K-band ($2.2μ$) images of spiral galaxies provide reliable maps of stellar surface mass density features such as massive spiral arms or bars. The main distorting agents in the mapping at shorter wavelengths are dust extinction and luminous young stars. From modeling the color changes across the main dust lanes in M51, we find that the K-band flux is attenuated by only $\ltorder 10\%$ even in the dust lanes. From monitoring the gravity-sensitive CO$(2.3μ)$ index across the spiral arms we find that young, red supergiants do not distort significantly the K-band image except in one small patch. On this basis, {\it we conclude that K band images do trace the massive disk star population}. In M51 we find the surface mass density contrast (arm/inter-arm) to range from 1.8 to 3, comparable to results from N-body simulations of the galaxy's tidal encounter with NGC~5195. The spiral arm amplitude in M51 also shows smooth, strong radial variations, with a maximum at $\sim 130\asec$ and minima at $45\asec$ and $170\asec$.

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