Protogalaxies Research Articles

Upper Limits on the LYα Emission at Z = 3.4

Many searches have been carried out to detect emission from massive primeval hydrogen clouds at high redshift. By observing the 21 cm line it has been possible to impose strong upper limits on the mass and number of protoclusters at high redshift (Wieringa, et al. 1992). Since strong Lyα emission is expected from primeval galaxies undergoing their first burst of star formation, many attempts to detect this emission have been made, but no positive detection has been reported, imposing strong constraints on models of galaxy formation (see Djorgovski et al. 1993 for a review).

The Ultraviolet Sky as Observed by the Shuttle-Borne Ultraviolet Imaging Telescope

view Abstract Citations (25) References (37) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Ultraviolet Sky as Observed by the Shuttle-Borne Ultraviolet Imaging Telescope Waller, W. H. ; Marsh, M. ; Bohlin, R. C. ; Cornett, R. H. ; Dixon, W. V. ; Isensee, J. E. ; Murthy, J. ; O'Connell, R. W. ; Roberts, M. S. ; Smith, A. M. ; Stecher, T. P. Abstract Analysis of 489 wide-field images obtained by the Shuttle-borne Ultraviolet Imaging Telescope (UIT) has yielded positive detections of FUV and NUV backgrounds in both the orbital daytime and nighttime skies. The daytime backgrounds can be attributed to atmospheric dayglow line emission (in the FUV) and solar stray-light contamination (in the NUV). A few of the nighttime backgrounds (in both bands) appear to be affected by stray light from UV-bright stars just beyond the imaged fields of view. In both bands, the highest nighttime background levels are found in nebular fields at low galactic latitude. The diffuse backgrounds in these fields are probably associated with the adjoining nebulosity. Away from the galactic plane, the nighttime FUV backgrounds are confused by O I nightglow emission and possible photometric errors. The more tightly constrained NUV intensities correlate with those predicted from corresponding optical measurements of the Zodiacal light, yielding a NUV/Vis "color" of 0.5 +/- 0.2 for the Zodiacal light. After subtraction of the predicted Zodiacal component, the residual NUV intensities correlate with FIR measurements of the corresponding fields. Extrapolation to negligible FIR intensities yields an extragalactic NUV component of 300 photon units or less. This upper limit supports the low intensities that have been proposed in the debate over the strength and structure of the UV background (cf. Henry, ARA&A, 29,89, 1991; Bowyer, ARA&A, 29,59 1991). Such low values reinforce the characterization of the ultraviolet sky as the "window" of choice in the search for nearby low- surface-brightness galaxies and faint primeval galaxies much farther away. Publication: The Astronomical Journal Pub Date: September 1995 DOI: 10.1086/117601 Bibcode: 1995AJ....110.1255W Keywords: ULTRAVIOLET GENERAL; TELESCOPES; ULTRAVIOLET: SOLAR SYSTEM full text sources ADS | data products SIMBAD (41) NED (21) MAST (1)

A Near-Infrared Search for Line Emission from Protogalaxies Using the W. M. Keck Telescope

We present the first results from a near-infrared narrow-band search for primeval galaxies (PGs) using the Keck 10~m telescope. We have targeted our fields for three QSOs and one radio galaxy at redshifts $z = 2.28$ to $4.70$. We selected narrow-band filters in the $K$-band centered on strong emision lines at the redshift of the targets. We reach limiting fluxes between $1.6\times 10^{-17}$~erg~s$^{-1}$~cm$^{-2}$ and $1.0\times 10^{-16}$~erg~s$^{-1}$~cm$^{-2}$, and cover a total area of $\sim 4$~arcmin$^2$. At the redshifts of interest, these flux limits correspond to typical restframe line luminosities of $\sim 10^{42} - 10^{43}$~erg~s$^{-1}$, unobscured star formation rates of $\sim 1 - 100$ $M_\odot$~yr$^{-1}$, and a sampled comoving volume of several tens of Mpc$^3$. We have found no candidate PGs at a $2\sigma$ confidence level. We demonstrate that for moderate dust absorption ($A_V \gsim 2^m$) in a simple dust-screen model, our preliminary survey puts a strong constraint on intrinsic PG luminosities during an intial burst of star formation. In the case of the QSOs, we have used PSF-subtraction to search for the presence of faint, extended line emission surrounding these radio-quiet AGNs. We find no evidence for extended emission down to $3.7 \times 10^{-17}$~erg~s$^{-1}$~cm$^{-2}$. This imposes limits on the reprocessed fraction of the QSO continuum emission ranging between $0.02$\% and $0.29$\%; if beaming effects are not important, then this implies similarly small covering factors for clouds optically thick to the QSO continuum emission.

Infrared line emission from high-redshift galaxies. 1: Calculations

view Abstract Citations (18) References (57) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Infrared Line Emission from High-Redshift Galaxies. I. Calculations Mannucci, Filippo ; Beckwith, Steven V. W. Abstract The first generation of stars at high redshift should have produced bright optical lines of common elements. These lines would appear now in near-infrared bands. We estimate the line fluxes and large-area surface brightnesses of the prominent lines Lyα, Hα, Hβ, [O III] λ5007, and [O II] λ3727 from the first galaxies under a variety of assumptions about the epochs of star formation and cosmology. The results show that these galaxies are within the reach of the present generation of infrared instrumentation for a wide range of star formation histories. We discuss the efficacy of searching for emission-line objects in the near-infrared as a means of finding primeval galaxies and discuss the possible searching strategies with respect to the expected intrinsic scatter of the properties of the forming galaxies. Publication: The Astrophysical Journal Pub Date: April 1995 DOI: 10.1086/175460 Bibcode: 1995ApJ...442..569M Keywords: Emission Spectra; Galactic Evolution; Infrared Astronomy; Infrared Spectra; Line Spectra; Star Formation; Stellar Composition; Astronomical Spectroscopy; Cosmic Dust; Near Infrared Radiation; Star Distribution; Stellar Luminosity; Astrophysics; GALAXIES: EVOLUTION; GALAXIES: STELLAR CONTENT; INFRARED: GALAXIES; LINE: FORMATION full text sources ADS | data products SIMBAD (1)

Radiative transfer in a clumpy universe: The colors of high-redshift galaxies

We assess the effects of the stochastic attenuation produced by intervening QSO absorption systems on the broadband colors of galaxies at cosmological distances. We compute the H I opacity of a clumpy universe as a function of redshift, including scattering in resonant lines, such as Lyman alpha, Lyman beta, Lyman gamma, and higher order members, and Lyman-continuum absorption. Both the numerous, optically thin Lyman-alpha forest clouds and the rarer, optically thick Lyman limit systems are found to contribute to the obscuration of background sources. We study the mean properties of primeval galaxies at high redshift in four broad optical passbands, U(sub n), B, G, and R. Even if young galaxies radiated a significant amount of ionizing photons, the attenuation due to the accumulated photoelectric opacity along the path is so severe that sources beyond z approximately 3 will drop out of the U(sub n) image together. We also show that the observed B-R color of distant galaxies can be much redder than expected from a stellar population. At z approximately 3.5, the blanketing by discrete absorption lines in the Lyman series is so effective that background galaxies appear, on average, 1 mag fainter in B. By z approximately 4, the observed B magnitude increment due to intergalactic absorption exceeds 2 mag. By modeling the intrinsic UV spectral energy distribution of star-forming galaxies with a stellar population synthesis code, we show that the (B-R)(sub AB) approximately 0 criterion for identifying 'flat-spectrum,' metal-producing galaxies is biased against objects at z greater than 3. The continuum blanketing from the Lyman series produces a characteristic staircase profile in the transmitted power. We suggest that this cosmic Lyman decrement might be used as a tool to identify high-z galaxies.

Galaxy Evolution from Deep Galaxy Counts

We present deep galaxy number counts and colours of K – band selected galaxy surveys. We argue that primeval galaxies are present within the survey data, but have remained unidentified. There are few objects with the colours of an L∗ elliptical galaxy at a redshift of z ≈ 1, in contradiction to standard luminosity evolution models. We present K – band photometry of the objects in a spectroscopic redshift survey selected at 21 < B < 22.5. The absolute K magnitudes of the galaxies are consistent with the no-evolution or pure luminosity evolution models. The excess faint blue galaxies seen in the B – band number counts at intermediate magnitudes are a result of a low normalization, and do not dominate the population until B ≈ 25. Extreme merging or excess dwarf models are not needed at z < 1.

THE SEARCH FOR PRIMEVAL GALAXIES

ABSTRACT Isolated examples of young star-forming galaxies have been discovered, but the predicuted widespread population of primeval galaxies (estimated to have surface densities in the range 104-5 deg-2) has so far escaped detection. This paper deals with the search for this extensive (and, so far, elusive) population, and concentrates on the formation of spheroidal systems (bulges and halos) since there is considerable evidence that disk formation was more quiescent. The review begins with a summary of the expected model independent properties of primeval galaxies. Particular attention is paid to the redshift of galaxy formation; empirical evidence is presented that supports galaxy formation at z < 5; however, there exist persuasive arguments that at least some galaxy formation must have taken place at higher redshifts. A major part of this review concerns primeval galaxy search strategies. Most (although not all) constraints on the properties of primeval galaxies come from searches for Ly-alpha emitting objects. Flux limits for these searches have now reached levels at which surveys should, according to simple models, have detected a total of 101-3 objects; yet no really good candidates have been found. This discrepancy between models and observations can possibly be explained by a combination of (i) dust absorption, and (ii) finite angular extent, which degrades flux limits. Technological advances in sub-mm instrumentation should result in the detection of the far-IR flux of primeval galaxies in the next few years.

Infrared measurements from the Cosmic Background Explorer (COBE)

The Cosmic Background Explorer (COBE) satellite was developed by NASA's Goddard Space Flight Center to measure the diffuse IR and microwave radiation from the early universe, to the limits set by our astrophysical environment. It was launched 18 November 1989 and carried three instruments, a FIR Absolute Spectrophotometer (FIRAS) to compare the cosmic microwave background radiation with a precise blackbody, a Differential Microwave Radiometer (DMR) to map the cosmic radiation precisely, and a Diffuse Infrared Background Experiment (DIRBE) to search for the accumulated light of primeval galaxies. The cosmic microwave background radiation spectrum was measured 1000 times more precisely than was possible before the COBE launch. The microwave background was found to have an intrinsic anisotropy for the first time, at a level of a part in 10 5 with a smoothing of 10°. A comprehensive set of absolutely calibrated IR sky maps has been acquired to search for the cosmic IR background.

New limits on galaxy formation at high redshift

The results from the first search for |${\rm Ly}\alpha$| emission from primeval galaxies at redshifts of |$z \ge 7$| are presented. The aim of this search is to detect |${\rm Ly}\alpha$| emission from the progenitors of the general present-day galaxy population. We have undertaken deep imaging with IRCAM in the near-infrared J window (⁠|$\sim1.0-1.5 \, {{\rm \mu m}}$|⁠), using four narrow-band filters of 2 per cent FWHM. Over an area of sky of |$3.0 \, {\rm arcmin}^2$| we find no young galaxies to a sensitivity limit of |$\simeq 10^{-18} {\rm W \, m}^{-2}$|⁠. This sensitivity corresponds to star formation at redshifts of |$7.2 \le z \le 9.3$| of only a few times the rate observed in spiral galaxies. At least one-third of the progenitors of bright galaxies must have had |${\rm Ly}\alpha$| luminosities of |$< 7.5 \times 10^{37} \, {\rm W} \, (\Omega=1, H_0=50 \, {\rm km} \, {\rm s}^{-1} \, {\rm Mpc}^{-1}$)| at these redshifts. Our limits on the luminosities of young galaxies at |$z \ge 7$| are comparable to the lower redshift limits of optical searches. By combining the upper limits in the optical and near-infrared passbands, it is now apparent that if the |${\rm Ly}\alpha$| emission from young galaxies is unattenuated by dust then galaxies could not have been many times brighter than present-day galaxies at any time over a large fraction of the age of the Universe (⁠|$2 \le z \le 9$|⁠).

Searches for primeval galaxies in the near infrared

view Abstract Citations (34) References (32) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Searches for Primeval Galaxies in the Near Infrared Thompson, D. ; Djorgovski, S. ; Beckwith, S. V. W. Abstract We discuss the feasibility of detecting the progenitors of normal elliptical galaxies (PGs) undergoing their first massive starbursts at large redshifts using narrow-band imaging in the near infrared. Four strong emission lines are plausible tracers of such objects, viz. [O II] λ3727, Hβ λ4861, [O 111] λ5007, and Hα λ6563, spanning the redshift range z ~ 1-5.5 in the standard JHK bands. The expected line fluxes are in the range F~10^-16+/-1.5^ erg/cm^2^/s, depending on the star-formation history, emission line, amount of dust present, redshift, and cosmology. The brighter end of this flux range is already within the reach of existing technology. We estimate the expected surface density of protogalaxies on the sky and several other related quantities. We report on the results of a pilot project done at Palomar to search in the K band for [O II] λ3727 emission line galaxies in the fields of three z > 4 quasars, using a narrow-band ({DELTA}z = 0.013) imaging technique. The total area surveyed is 0.72 arcmin^2^, with a limiting line flux (90% confidence limit) in the range F ~ (4x10) x 10^-16^ erg/cm^2^/s. The total comoving volume covered is V ~ 100 Mpc^3^, down to limiting rest frame line luminosities in the range L ~ (0.3-30) x 10^43^ erg/s, or implied unobscured star-formation rates in the range SFR~(30-15000) M_sun_/yr, for a Friedman cosmology with H_0_ = 75 km/s/Mpc, {OMEGA}_0_ = 0.2, and {DELTA}_0_ = 0. No viable candidate protogalaxies were found, though this was not entirely unexpected given our limited field size and line flux limits, but the limits achieved are an improvement over previously published surveys. Forthcoming experiments should be able to extend these limits by two or more orders of magnitude in comoving volume coverage and one or two orders of magnitude in limiting flux, and could detect young ellipticals if our calculations are representative of their emission-line properties. Publication: The Astronomical Journal Pub Date: January 1994 DOI: 10.1086/116830 Bibcode: 1994AJ....107....1T Keywords: Elliptical Galaxies; Emission Spectra; Galactic Evolution; Line Spectra; Red Shift; Star Formation; Active Galactic Nuclei; Cosmology; Imaging Techniques; Near Infrared Radiation; Sky Surveys (Astronomy); Spectrum Analysis; Star Formation Rate; Stellar Luminosity; Astrophysics; GALAXIES: FORMATION; COSMOLOGY: OBSERVATIONS full text sources ADS | data products SIMBAD (6) NED (3)

A nearby protogalaxy?

A nearby protogalaxy?

Extended Hα emission from IRAS F10214 + 4724: starburst or active galactic nucleus?

We present a narrow-band (λ/∆λ = 1025) image of Hα emission from the ultraluminous galaxy IRAS F10214 + 4724. The Hα-emitting region is extended over 1.8 arcsec ( ~ 10 kpc). From a comparison with other data, we conclude that the FWHM of the bulk of the Hα is at most ~ 450 km s–1, though we cannot rule out a much weaker broad component. These results suggest the presence of a global starburst in IRAS F10214 + 4724. The Hα, radio continuum and bolometric luminosity can be explained by a starburst with a normal IMF but an enormous star formation rate. The inferred burst duration, total mass of stars formed during the burst and measured extent of the Hα emission support the view of IRASF10214+4724 as a primeval galaxy undergoing its initial starburst. We also examine the implications of our results for AGN interpretations of IRAS F 10214 + 4724. In this case, IRAS F 10214 + 4724 provides evidence for the continuity in properties of AGN as the luminosity increases from Seyfert to QSO. In this model, IRAS F 10214 + 4724 could be interpreted as a QSO with an obscured broad-line region. The high Hα/radio flux ratio of IRAS F 10214 + 4 724 is used to argue in favour of the starburst interpretation, but the presence of an AGN is not ruled out.

A search for primeval galaxies using a narrow-band imaging technique

We have imaged nine fields through a system of narrow-band filters, in order to search for Lyα emission from primeval galaxies at 2.2≤z≤3.3. We report here on our inability to detect emission-line objects down to a 1σ brightness threshold of 5.6×10 −17 erg cm −2 s −1 arcsec −2 , with a limiting space density of less than 20 objects per square degree. These results are in disagreement with simple models by about a factor of 10

Submillimeter spectrum and dust mass of the primeval galaxy IRAS 10214 + 4724

view Abstract Citations (76) References (18) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Submillimeter Spectrum and Dust Mass of the Primeval Galaxy IRAS 10214+4724 Downes, D. ; Radford, J. E. ; Greve, A. ; Thum, C. ; Solomon, P. M. ; Wink, J. E. Abstract We measured with the IRAM 30 m telescope the continuum flux of the extremely luminous primeval galaxy IRAS 10214+4724 at a wavelength of 1.2 mm. This is the longest wavelength at which this galaxy's thermal continuum radiation has been detected; at z = 2.286, it corresponds to a rest wavelength of 370 microns. From the entire continuum spectrum we estimate a dust temperature of 80 K, and from the optically thin radiation at 370 microns (rest frame) we find a dust mass of 2.5 X 10^8^ h^-2^ M_sun_. For the H_2_ mass of 1 X 10^11^ h^-2^ M_sun_ implied by the CO line luminosity, this yields a ratio of the mass of gas (H_2_ + He) to warm dust of 500, which is surprisingly normal for a galaxy at z = 2.3. It is the same value as observed in the central regions of nearby luminous galaxies that have solar metallicity. The ratio of observed CO and 370 microns (restframe) luminosities in 10214 + 4724, essentially the gas-to-dust mass ratio, is the same as in nearby galaxies. Hence, In this galaxy, most of the heavy elements have already been produced, at nearly present-day abundances. Publication: The Astrophysical Journal Pub Date: October 1992 DOI: 10.1086/186568 Bibcode: 1992ApJ...398L..25D Keywords: Cosmic Dust; Infrared Sources (Astronomy); Starburst Galaxies; Submillimeter Waves; Abundance; Astronomical Models; Carbon Monoxide; Interstellar Extinction; Metallicity; Astrophysics; GALAXIES: FORMATION; GALAXIES: INDIVIDUAL ALPHANUMERIC: 10214; 4724; GALAXIES: INTERSTELLAR MATTER; GALAXIES: STARBURST; INFRARED: GALAXIES; ISM: DUST; EXTINCTION full text sources ADS | data products SIMBAD (9) NED (1)

Warm molecular gas in the primeval galaxy IRAS 10214 + 4724

We observed CO(6 - 5) and CO(3 - 2) emission at z = 2.286 from the extremely luminous infrared galaxy IRAS 10214+4724. We show that the CO(3 - 2) line is always comparable in strength to the 1-0 line, in galaxies at high redshift, due to the warmer microwave background. The CO(6 - 5) line traces warm molecular gas, which is found in the Milky Way only in regions of high-mass star formation. The molecular gas in 10214+4724 is warm and dense with n(H_2_) ~ 5000 cm^-3^ if T_kin_ = 50 K. The total mass of molecular hydrogen is M(H_2_) = 1 x 10^11^ h^-2^ M_sun_. Although this is about 200 times less mass than initially estimated by Brown &amp; VandenBout (1991), it is still 3-5 times larger than the molecular mass of any other galaxy yet observed and 60 h^-2^ more than the H_2_ mass of the Milky Way. A starburst can power 10214+4724 only if predominantly high-mass stars are produced. This extraordinary primeval galaxy has most of its mass in molecular gas, has already collapsed, and is undergoing an extreme starburst that is generating metals in abundances close to solar.

Submillimetre observations of the z = 2.286 IRAS galaxy 10214 + 4724

Results of submillimetre observations of the very high-redshift IRAS galaxy 10214 + 4724 are presented. Significant detections at 800 μm (30 ± 7 mJy, 4.3 σ) and 450 μm (365 ± 100 mJy, 3.6 σ) have been achieved. We compare the data to the existing models of this galaxy and find that both the extreme primeval galaxy model and the dust-embedded Seyfert model are excluded. We conclude that the galaxy is likely to be undergoing an extreme starburst, but whether this represents the formation of a significant fraction of the stars is unclear.

QSO absorption systems and the origin of the ionizing background at high redshift

Two candidates are considered for the sources of the ionizing background: primeval galaxies and AGN-type objects. The spectrum of the diffuse radiation field is computed taking into account the opacity of intervening Ly-alpha clouds and Lyman limit systems. The possibility is assessed that the QSO heavy-element absorption systems are photoionized by a metagalactic flux which is dominated by the UV radiation from hot stars in young galaxies. Grids of photoionization models for metal-line systems are presented, and it is argued that the relative column densities of the most abundant ions predicted by the models are compatible with the observational constraints. The inferred physical properties of the absorbing clouds are discussed. Given that the observed QSOs cannot provide the required number of ionizing photons at high redshift, the results obtained support a scenario in which young star-forming galaxies are the main sources of the UV radiation background at early epochs. 21 refs.

Search of the 3-point correlation function for quasars

view Abstract Citations (8) References (18) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Search For the 3-Point Correlation Function for Quasars Borderia, Maria J. P. ; Iovino, Angela ; Bonometto, Silvio A. Abstract Detecting a 3-point correlation function for a set of clustered objects gives significant information on the nature of the clustering. Analyzing available quasar samples, we find that their 3-point correlation function does not vanish, but is likely to be smaller than for ordinary galaxies. A clustering model based on the Kirkwood superposition hypothesis, as expected for objects related to very high fluctuation peaks, seems to be excluded. Rather, the possibility that quasars are a phenomenon associated with primeval galaxy evolution seems favored. The analysis is significant also from a technical point of view, it outlines some difficulties found when analyzing a sample consisting of many small subsamples, and how they can be possibly overcome. Publication: The Astronomical Journal Pub Date: August 1991 DOI: 10.1086/115888 Bibcode: 1991AJ....102..495B Keywords: Astronomical Models; Galactic Clusters; Galactic Evolution; Quasars; Correlation Coefficients; Red Shift; Universe; Astrophysics; GALAXIES: EVOLUTION; QUASARS full text sources ADS |

Spatially resolved optical images of high-redshift quasi-stellar objects

U and B continuum and Ly-alpha images obtained with the UV-flooded TI2 CCD at the prime focus of the 4-m telescope at KPNO during May and November 1988 are reported for 19 radio-loud high-redshift QSOs. The data are presented in extensive contour maps, radial surface-brightness profiles, and tables and discussed in detail. Ly-alpha emission with typical luminosity about 10 to the 44th erg/sec and spatial extent about 100 kpc is spatially resolved in 15 QSOs, and these nebulae are attributed to the photoionization of the interstellar or intergalactic medium of young or proto galaxies by radiation escaping anisotropically along the radio axis of the QSO. The mechanisms possibly responsible for the Ly-alpha emission and for the UV fuzz seen around some of the QSOs are explored. 84 refs.

Spectroscopic limits on high-redshift Ly-alpha emission

We have conducted a deep long-slit spectroscopic search for high- redshift (2.7 &lt; z &lt; 4.7) Lyα emission. Four pairs of deep, high- resolution (R ~ 2000), long-slit CCD frames were taken at the Multiple Mirror Telescope. The "blank sky" in each pair of frames was searched for faint emission features unresolved spatially and spectrally. No emission features were found down to a limiting line surface brightness (1 σ) of 1-4 x 10^-18^ ergs s^-1^ cm^-2^ arcsec^-2^. The sensitivity of the search was calibrated using simulations with synthetic features added to the data frames. The data set upper limits on the mean space density &lt;n&gt; and line flux of randomly distributed Lyα-emitting clouds; for example, at z ~ 4.5 we have a 95% confidence limit of &lt;n&gt; &lt; 1 Mpc^-3^ h^3^_100_ at a total line flux level of ~ 3 x 10^-17^ ergs s^-1^ cm^-2^. These limits approach expected emission levels for fairly conservative published primeval galaxy models. In addition, Lyα emission was searched for, but not detected, from a known Lyα-limit absorption cloud toward QSO 0731+653. Assuming that the gas in this cloud is spatially resolved (size ~4h-1 kpc) we set an upper limit on the diffuse ionizing flux density at z = 2.912 of J<SUB>nu</SUB>_ &lt;~ 2 x 10^-19^ ergs s^-1^ cm^-2^ sr^-1^ Hz^-1^.