Spectrophotometry of nearby field galaxies: the data

We have obtained integrated and nuclear spectra, as well as U, B, R surface photometry, for a representative sample of 196 nearby galaxies. These galaxies span the entire Hubble sequence in morphological type, as well as a wide range of luminosities (M_B=-14 to -22). Here we present the spectrophotometry for these galaxies. The selection of the sample and the U, B, R surface photometry is described in a companion paper (Paper I). Our goals for the project include measuring the current star formation rates and metallicities of these galaxies, and elucidating their star formation histories, as a function of luminosity and morphology. We thereby extend the work of Kennicutt (1992a) to lower luminosity systems. We anticipate that our study will be useful as a benchmark for studies of galaxies at high redshift. We describe the observing, data reduction and calibration techniques, and demonstrate that our spectrophotometry agrees well with that of Kennicutt. The spectra span the range 3550--7250 A at a resolution (FWHM) of ~6 A, and have an overall relative spectrophotometric accuracy of +/- 6 per cent. We present a spectrophotometric atlas of integrated and nuclear rest-frame spectra, as well as tables of equivalent widths and synthetic colors. We study the correlations of galaxy properties determined from the spectra and images. Our findings include: (1) galaxies of a given morphological class display a wide range of continuum shapes and emission line strengths if a broad range of luminosities are considered, (2) emission line strengths tend to in- crease and continua tend to get bluer as the luminosity decreases, and (3) the scatter on the general correlation between nuclear and integrated H_alpha emission line strengths is large.Comment: Accepted for publication in ApJS (scheduled for Vol.127, 2000 March); 63 pages, LateX, 9 figures and 6 tables included, a spectrophotometric atlas is provided as GIF images, fig 1 as a JPEG image, in a single tar-file; a full 600 dpi version is available at http://www.astro.rug.nl/~nfgs

Low Star Formation Rates for z=1 Early-Type Galaxies in the Very Deep GOODS-MIPS Imaging: Implications for their Optical/Near-Infrared Spectral Energy Distributions

We measure the obscured star formation in z~1 early-type galaxies. This constrains the influence of star formation on their optical/near-IR colors, which, we found, are redder than predicted by the model by Bruzual & Charlot (2003). From deep ACS imaging we construct a sample of 95 morphologically selected early-type galaxies in the HDF-N and CDF-S with spectroscopic redshifts in the range 0.85<z<1.15. We measure their 24 micron fluxes from the deep GOODS-MIPS imaging and derive the IR luminosities and star formation rates. The fraction of galaxies with >2 sigma detections (~25 muJy} is 17(-4,+9)%. Of the 15 galaxies with significant detections at least six have an AGN. Stacking the MIPS images of the galaxies without significant detections and adding the detected galaxies without AGN we find an upper limit on the mean star formation rate (SFR) of 5.2+/-3.0 Msol yr^-1, and on the mean specific SFR of 4.6+/-2.2 * 10^-11 yr^-1. Under the assumption that the average SFR will decline at the same rate as the cosmic average, the in situ growth in stellar mass of the early-type galaxy population is less than 14+/-7% between z=1 and the present. We show that the typically low IR luminosity and SFR imply that the effect of obscured star formation (or AGN) on their rest-frame optical/near-IR SEDs is negligible for ~90% of the galaxies in our sample. Hence, their optical/near-IR colors are most likely dominated by evolved stellar populations. This implies that the colors predicted by the Bruzual & Charlot (2003) model for stellar populations with ages similar to those of z~1 early-type galaxies (~1-3 Gyr) are most likely too blue, and that stellar masses of evolved, high-redshift galaxies can be overestimated by up to a factor of ~2.Comment: Accepted for publication in ApJ, 8 pages, 4 figures, 1 tabl

Ellipticals with Kinematically-Distinct Cores: (V-I) Color Images with WFPC2

We have analysed HST/WFPC2 F555W and F814W images for fifteen elliptical galaxies with kinematically-distinct cores. For each of them we have derived surface brightness and isophotal parameter profiles in the two bands, color maps, and radial profiles in (V-I). We have detected photometric evidence for faint stellar disks, on scales of a few tens to a few arcseconds, in seven galaxies, namely NGC 1427, 1439, 1700, 4365, 4406, 4494 and 5322. In NGC 1700, the isophotes are slightly boxy at the scale of the counter-rotating component, and disky at larger radii. We find no difference in (V-I) color greater than 0.02 mag between these disks and the surrounding galactic regions. Hence the stellar populations in the kinematically distinct cores are not strongly deviant from the population of the main body. For one galaxy, NGC 4365, the innermost region is bluer than the surrounding regions. This area extends to about 15pc, and contains a luminosity of 2.5x10^6 L$_\odot$. If interpreted as a stellar population effect, an age difference of $\sim$ 3-4 Gyrs, or an $[Fe/H]$ variation of about 0.2 dex, is derived. The nuclear intensity profiles show a large variety: some galaxies have steep cusp profiles, others have shallow cusps and a ``break radius''. The nuclear cusps of galaxies with kinematically-distinct cores follow the same trends as the nuclei of normal galaxies. We have not been able to identify a unique, qualifying feature in the WFPC2 images which distinguish the galaxies with kinematically distinct cores from the kinematically normal cores. [shortened]Comment: 56 pages, latex, 17 figures; figure 1 available upon request; ApJ, 481 in pres

Faint InfraRed Extragalactic Survey: Data and Source Catalogue of the MS1054-03 field

We present deep near-infrared Js, H, and Ks band imaging of a field around MS1054-03, a massive cluster at z=0.83. The observations were carried out with ISAAC at the ESO VLT as part of the Faint InfraRed Extragalactic Survey (FIRES). The total integration time amounts to 25.9h in Js, 24.4h in H, and 26.5h in Ks, divided nearly equally between four pointings covering 5.5'x5.3'. The 3-sigma total limiting AB magnitudes for point sources from the shallowest to deepest pointing are Js=26.0-26.2, H=25.5-25.8, and Ks=25.3-25.7. The effective spatial resolution of the coadded images has FWHM=0.48", 0.46", and 0.52" in Js, H, and Ks. We complemented the ISAAC data with deep optical imaging using existing HST WFPC2 mosaics in the F606W and F814W filters and new U, B and V band data from VLT FORS1. We constructed a Ks-band limited multicolour source catalogue to Ks(total,AB)=25 (about 5-sigma for point sources). The catalogue contains 1858 objects, of which 1663 have eight-band photometry. We describe the observations, data reduction, source detection and photometric measurements method. We present the number counts, colour distributions, and photometric redshifts z_ph of the catalogue sources. We find that our counts at the faint end 22<Ks(AB)<25, with slope dlog(N)/dm=0.20, lie at the flatter end of published counts in other deep fields and are consistent with those we derived in the HDF-South, the other FIRES field. Spectroscopic redshifts z_sp are available for about 330 sources in the MS1054-03 field; comparison between the z_ph and z_sp shows very good agreement, with =0.078. The MS1054-03 field observations complement our HDF-South data set with nearly five times larger area at about 0.7 brighter magnitudes. [ABRIDGED]Comment: Accepted for publication in the Astronomical Journal. 32 pages, 14 b/w figures, 1 color figur

VLT and NTT Observations of Two EIS Cluster Candidates. Detection of the Early-Type Galaxies Sequence at z~1

Optical data from the ESO VLT-UT1 Science Verification observations are combined with near-infrared data from SOFI at the NTT to obtain optical-infrared color-magnitude diagrams for the objects in the fields of two EIS cluster candidates. In both cases, evidence is found for a well-defined sequence of red galaxies that appear to be significantly more clustered than the background population. These results suggest that the two systems are real physical associations. The (R-Ks), (I-Ks) and (J-Ks) colors of the red sequences are used, in conjunction with similar data for spectroscopically confirmed clusters, to obtain redshift estimates of z ~ 0.9 and z ~ 1.0 for these two systems. These results make these EIS cluster candidates prime targets for follow-up spectroscopic observations to confirm their reality and to measure more accurately their redshift.Comment: 6 pages, 5 figures, to appear in Astronomy & Astrophysics (Special Letters Edition on "First Science with the VLT"

Rest-Frame Optical Emission Lines in z~3.5 Lyman Break selected Galaxies: The Ubiquity of Unusually High [OIII]/Hbeta Ratios at 2 Gyr

We present K-band spectra of rest-frame optical emission lines for 24 star-forming galaxies at z~3.2-3.7 using MOSFIRE on the Keck 1 telescope. Strong rest-frame optical [O III] and Hbeta emission lines were detected in 18 LBGs. The median flux ratio of [O III]5007 to Hbeta is 5.1+/-0.5, a factor of 5-10x higher than in local galaxies with similar stellar masses. The observed Hbeta luminosities are in good agreement with expectations from the estimated star-formation rates, and none of our sources are detected in deep X-ray stacks, ruling out significant contamination by active galactic nuclei. Combining our sample with a variety of LBGs from the literature, including 49 galaxies selected in a very similar manner, we find a high median ratio of [OIII]/Hbeta = 4.8+0.8-1.7. This high ratio seems to be an ubiquitous feature of z~3-4 LBGs, very different from typical local star-forming galaxies at similar stellar masses. The only comparable systems at z~0 are those with similarly high specific star-formation rates, though ~5x lower stellar masses. High specific star-formation rates either result in a much higher ionization parameter or other unusual conditions for the interstellar medium, which result in a much higher [OIII]/Hbeta line ratio. This implies a strong relation between a global property of a galaxy, the specific star-formation rate, and the local conditions of ISM in star-forming regions.Comment: 14 pages, 8 figures, 5 color, published in ApJ, updated to reflect published versio

The Evolution of Rest-Frame K-band Properties of Early-Type Galaxies from z=1 to the Present

We measure the evolution of the rest-frame K-band Fundamental Plane from z=1 to the present by using IRAC imaging of a sample of early-type galaxies in the Chandra Deep Field-South at z~1 with accurately measured dynamical masses. We find that $M/L_K$ evolves as $\Delta\ln{(M/L_K)}=(-1.18\pm0.10)z$, which is slower than in the B-band ($\Delta\ln{(M/L_B)}=(-1.46\pm0.09)z$). In the B-band the evolution has been demonstrated to be strongly mass dependent. In the K-band we find a weaker trend: galaxies more massive than $M=2\times10^{11}M_{\odot}$ evolve as $\Delta\ln{(M/L_K)}=(-1.01\pm0.16)z$; less massive galaxies evolve as $\Delta\ln{(M/L_K)}=(-1.27\pm0.11)z$. As expected from stellar population models the evolution in $M/L_K$ is slower than the evolution in $M/L_B$. However, when we make a quantitative comparison, we find that the single burst Bruzual-Charlot models do not fit the results well, unless large dust opacities are allowed at z=1. Models with a flat IMF fit better, Maraston models with a different treatment of AGB stars fit best. These results show that the interpretation of rest-frame near-IR photometry is severely hampered by model uncertainties and therefore that the determination of galaxy masses from rest-frame near-IR photometry may be harder than was thought before.Comment: 5 pages, 3 figures, Accepted for publication in ApJ