arXiv subjects

G. Feulner

Publications and source records attributed to G. Feulner.

At least 19 recordsLinked to original sources

arXiv2007

The impact of Spitzer infrared data on stellar mass estimates - and a revised galaxy stellar mass function at 0 < z < 5

Aims: We estimate stellar masses of galaxies in the high redshift universe with the intention of determining the influence of newly available Spitzer/IRAC infrared data on the analysis. Based on the results, we probe the mass assembly history of the universe. Methods: We use the GOODS-MUSIC catalog, which provides multiband photometry from the U--filter to the 8 mum Spitzer band for almost 15,000 galaxies with either spectroscopic (for ~7 % of the sample) or photometric redshifts, and apply a standard model fitting technique to estimate stellar masses. We then repeat our calculations with fixed photometric redshifts excluding Spitzer photometry and directly compare the outcomes to look for systematic deviations. Finally we use our results to compute stellar mass functions and mass densities up to redshift z = 5. Results: We find that stellar masses tend to be overestimated on average if further constraining Spitzer data are not included into the analysis. Whilst this trend is small up to intermediate redshifts z < 2.5 and falls within the typical error in mass, the deviation increases strongly for higher redshifts and reaches a maximum of a factor of three at redshift z = 3.5. Thus, up to intermediate redshifts, results for stellar mass density are in good agreement with values taken from literature calculated without additional Spitzer photometry. At higher redshifts, however, we find a systematic trend towards lower mass densities if Spitzer/IRAC data are included.

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arXiv2006

The Kormendy relation of massive elliptical galaxies at z~1.5. Evidence for size evolution ?

We present the morphological analysis based on HST-NIC2 (0.075 arcsec/pixel) images in the F160W filter of a sample of 9 massive field (> 10^{11} M_\odot) galaxies spectroscopically classified as early-types at 1.2 within R_e of our galaxies and we compared them with those of early-types at lower redshifts. We find that the surface brightness of our galaxies should get fainter by 2.5 mag from z~1.5 to z~0 to match the surface brightness of the local ellipticals with comparable R_e, i.e. the local Kormendy relation. Luminosity evolution without morphological changes can only explain half of this effect, as the maximum dimming expected for an elliptical galaxy is ~1.6 mag in this redshift range. Thus, other parameters, possibly structural, may undergo evolution and play an important role in reconciling models and observations. Hypothesizing an evolution of the effective radius of galaxies we find that R_e should increase by a factor 1.5 from z~1.5 to z~0.

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arXiv2006

Extremely compact massive galaxies at z~1.4

The optical rest-frame sizes of 10 of the most massive (~5x10^{11}h_{70}^{-2}M_sun) galaxies found in the near-infrared MUNICS survey at 1.2<z<1.7 are analysed. Sizes were estimated both in the J and K' filters. These massive galaxies are at least a factor of 4_{-1.0}^{+1.9} (+-1 sigma) smaller in the rest-frame V-band than local counterparts of the same stellar mass. Consequently, the stellar mass density of these objects is (at least) 60 times larger than massive ellipticals today. Although the stellar populations of these objects are passively fading, their structural properties are rapidly changing since that redshift. This observational fact disagrees with a scenario where the more massive and passive galaxies are fully assembled at z~1.4 (i.e. a monolithic scenario) and points towards a dry merger scenario as the responsible mechanism for the subsequent evolution of these galaxies.

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arXiv2006

The evolution of the mass function split by morphology up to redshift 1 in the FORS Deep and the GOODS-S Fields

We study the evolution of the stellar mass density for the separate families of bulge-dominated and disk-dominated galaxies over the redshift range 0.25 < z < 1.15. We derive quantitative morphology for a statistically significant galaxy sample of 1645 objects selected from the FORS Deep and the GOODS-S Fields. We find that the morphological mix evolves monotonically with time: the higher the redshift, the more disk systems dominate the total mass content. At redshift about 1, massive objects (M_stellar > 7E10 M_solar) host about half of the mass contained in objects of similar mass in the local universe. The contribution from early and late type galaxies to the mass budget at z about 1 is nearly equal. We show that in situ star formation is not sufficient to explain the changing mass budget. Moreover we find that the star formation rate per unit stellar mass of massive galaxies increases with redshift only for the intermediate and early morphological types, while it stays nearly constant for late-type objects. This suggests that merging and/or frequent accretion of small mass objects has a key role in the shaping of the Hubble sequence as we observe it now, and also in decreasing the star formation activity of the bulge-dominated descendants of massive disk galaxies.

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arXiv2005

The evolution of the luminosity functions in the FORS Deep Field from low to high redshift: II. The red bands

We present the redshift evolution of the restframe galaxy luminosity function (LF) in the red r', i', and z' bands as derived from the FORS Deep Field (FDF). Using the deep and homogeneous I-band selected dataset of the FDF we are able to follow the red LFs over the redshift range 0.5 < z < 3.5. The results are based on photometric redshifts for 5558 galaxies derived from the photometry in 9 filters achieving an accuracy of Delta z / (z_spec+1) ~ 0.03 with only ~ 1 % outliers. Because of the depth of the FDF we can give relatively tight constraints on the faint-end slope alpha of the LF: The faint-end of the red LFs does not show a large redshift evolution and is compatible within 1 sigma to 2 sigma with a constant slope over the redshift range 0.5 < z < 2.0. Moreover, the slopes in r', i', and z' are very similar with a best fitting value of alpha= -1.33 +- 0.03 for the combined bands. There is a clear trend of alpha to steepen with increasing wavelength: alpha_(UV & u')=-1.07 +- 0.04 -> alpha_(g' & B)=-1.25 +- 0.03 -> alpha_(r' & i' & z')=-1.33 +- 0.03. We show that the wavelength dependence of the LF slope can be explained by the relative contribution of different SED-type LFs to the overall LF, as different SED types dominate the LF in the blue and red bands. Furthermore we also derive and analyze the luminosity density evolution of the different SED types up to z ~ 2. Based on the FDF data, we find only a mild brightening of M_star and decrease of phi_star with increasing redshift. Therefore, from ~ 0.5 to \~ 3 the characteristic luminosity increases by ~0.8, ~0.4 and ~0.4 magnitudes in the r', i', and z' bands, respectively. Simultaneously the characteristic density decreases by about 40 % in all analyzed wavebands. [abridged]

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arXiv2005

Dating the stellar population in massive early-type galaxies at $z\sim$1.5

We present the analysis of 10 massive early-type galaxies at $z\sim1.5$. They have been identified by means of a near-IR low resolution spectroscopic follow-up of a complete sample of 36 bright (K' $<$ 18.5) Extremely Red Objects (EROs, R-K'$>$ 5) selected from the Munich Near-IR ClusterSurvey (MUNICS; Drory et al. 2001). The low resolution near-IR spectra constrain their redshift at $1.2 2$ for all the galaxies and $z_{f} \geq 4$ for the oldest ones. The comparison of the 4000Åbreak and of the overall spectral shape of the average spectrum of the 10 galaxies at $z\sim1.5$ with those of their local counterpartsconfirms that field massive early-type galaxies formed the bulk of their stellar mass at $2<z<4$, most likely over a short ($<$ 1 Gyr) star formation time scale, consistently with the results derived from the analysis of their individual spectro-photometric properties.

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arXiv2005

Specific Star Formation Rates to Redshift 1.5

We present a study to determine how star formation contributes to galaxy growth since z=1.5 over five decades in galaxy stellar mass. We investigate the specific star formation rate (SSFR; star formation rate [SFR] per unit galaxy stellar mass) as a function of galaxy stellar mass and redshift. A sample of 175 K-band selected galaxies from the MUnich Near-Infrared Cluster Survey spectroscopic dataset provide intermediate to high mass galaxies (mostly M* > 10^10 Msun) to z=1. The FORS Deep Field provides 168 low mass galaxies (mostly M* < 10^10 Msun) to z=1.5. We use a Sloan Digital Sky Survey galaxy sample to test the compatibility of our results with data drawn from a larger volume. We find that at all redshifts, the SSFR decreases with increasing galaxy stellar mass suggesting that star formation contributes more to the growth of low mass galaxies than to the growth of high mass galaxies, and that high mass galaxies formed the bulk of their stellar content before z=1. At each epoch we find a ridge in SSFR versus stellar mass that is parallel to lines of constant SFR and evolves independently of galaxy stellar mass to a particular turnover mass. Galaxies above this turnover mass show a sharp decrease in the SFR compared to the average at each epoch and the turnover mass increases with redshift. The SFR along the SSFR ridge decreases by roughly a factor of 10, from 10 Msun/yr at z=1.5 to 1 Msun/yr at z=0. High mass galaxies could sustain the observed rates of star formation over the 10 Gyr observed, but low mass galaxies likely undergo episodic starbursts.

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arXiv2004

The stellar mass function of galaxies to z ~ 5 in the Fors Deep and GOODS-S fields

We present a measurement of the evolution of the stellar mass function (MF) of galaxies and the evolution of the total stellar mass density at 0 10^10 Msun which are the likely progenitors of todays L* galaxies are found in much smaller numbers above z=2. However, we note that massive galaxies with M>10^11 Msun are present even to the largest redshift we probe. Beyond z=2 the evolution of the mass function becomes more rapid. We find that the total stellar mass density at z=1 is 50% of the local value. At z=2, 25% of the local mass density is assembled, and at z=3 and z=5 we find that at least 15% and 5% of the mass in stars is in place, respectively. The number density of galaxies with M>10^11 Msun evolves very similarly to the evolution at lower masses. It decreases by 0.4 dex to z=1, by 0.6 dex to z=2, and by 1 dex to z=4.

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arXiv2004

The density of very massive evolved galaxies to z~1.7

We spectroscopically identified 7 massive evolved galaxies with magnitudes 17.8 ~1.5, a factor 1.5 lower than the density (8.4(+-1) x 10^{-5} Mpc^{-3}) of early-types with comparable masses at z=0. The incompleteness (30%) of our spectroscopic observations accounts for this discrepancy. Thus, our data do not support a decrease of the comoving density of early-type galaxies with masses comparable to the most massive ones in the local Universe up to z~1.7. This suggests that massive evolved galaxies do not play an important role in the evolution of the mass density outlined by recent surveys in this redshift range, evolution which instead has to be ascribed to the accretion of the stellar mass in late-type galaxies. Finally, the presence of such massive evolved galaxies at these redshifts suggests that the assembly of massive spheroids has taken place at z>2 supporting a high efficiency in the accretion of the stellar mass in massive halos in the early Universe.

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arXiv2004

Looking for obscured QSOs in the X-ray emitting ERO population

We present XMM-Newton data centered on one of the MUNICS Near Infrared Cluster Survey fields (S2F1) and we discuss the X-ray properties of the 6 X-ray emitting EROs found. For one of them we have already obtained the redshift using near-infrared spectroscopic data, while for the remaining 5 EROs the analysis is based on photometric redshifts. We find evidence for the presence of an X-ray obscured QSO in at least 5 out of the 6 X-ray emitting EROs. For these 5 objects we derive intrinsic (2-10 keV) luminosities in excess of 10^44 erg/s and intrinsic column densities higher than 10^22 cm^-2. These values have been obtained through a basic X-ray spectral analysis for the three brightest sources and through the analysis of the hardness ratios for the remaining two. All of these 5 X-ray emitting EROs appear extended in the optical/near-infrared bands indicating that the host galaxy emission dominates at these wavelengths. This suggests that the hosted AGNs are likely to be absorbed also in the optical/near-infrared bands: i.e. they are likely X-ray obscured possible type 2 QSOs. For the remaining ERO the presence of an AGN is suggested both by its high 0.5-2 keV luminosity (L(0.5-2 keV)~10^43 erg/s) and by its X-ray-to-optical flux ratio. In this case the quality of the present data prevents us from placing firm constraints on the AGN type hosted. Finally, the near-IR spectrum obtained for one of the 6 EROs classifies the host galaxy as an elliptical at z~1.7 with a stellar mass well in excess of 10^11 M_\odot. This result corroborates the possible link between the QSO activity and the formation of massive spheroids.

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arXiv2004

The star formation rate history in the FORS Deep and GOODS South Fields

We measure the star formation rate (SFR) as a function of redshift z up to z \~4.5, based on B, I and (I+B) selected galaxy catalogues from the FORS Deep Field (FDF) and the K-selected catalogue from the GOODS-South field. Distances are computed from spectroscopically calibrated photometric redshifts accurate to (Delta_z / (z_spec+1)) ~0.03 for the FDF and ~0.056 for the GOODS-South field. The SFRs are derived from the luminosities at 1500 Angstroem. We find that the total SFR estimates derived from B, I and I+B catalogues agree very well ($\lsim 0.1$ dex) while the SFR from the K catalogue is lower by ~0.2 dex. We show that the latter is solely due to the lower star-forming activity of K-selected intermediate and low luminosity (L L_*) galaxies is independent of the selection band, i.e. the same for B, I, (I+B), and K-selected galaxy samples. At all redshifts, luminous galaxies (L>L_*) contribute only ~1/3 to the total SFR. There is no evidence for significant cosmic variance between the SFRs in the FDF and GOODs-South field, ~0.1 dex, consistent with theoretical expectations. The SFRs derived here are in excellent agreement with previous measurements provided we assume the same faint-end slope of the luminosity function as previous works (alpha ~ -1.6). However, our deep FDF data indicate a shallower slope of alpha=-1.07, implying a SFR lower by ~0.3 dex. We find the SFR to be roughly constant up to z ~4 and then to decline slowly beyond, if dust extinctions are assumed to be constant with redshift.

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arXiv2004

On the constraining observations of the dark GRB 001109 and the properties of a z = 0.398 radio selected starburst galaxy contained in its error box

We present optical and NIR (near infrared) follow up observations of the GRB 001109 from 1 to 300 days after the burst. No transient emission was found at these wavelengths within this GRB's (Gamma Ray Burst) 50" radius BeppoSAX error box. Strong limits (3 sigma) are set with: R >~ 21, 10.2 hr after the GRB; I >~ 23, 11.4 hr after the GRB; H >~ 20.7, 9.9 hr after the GRB; and Ks >~ 20, 9.6 hours after the GRB. We discuss whether the radio source found in the GRB's error box (Taylor et al. 2000) might be related to the afterglow. We also present a multiwavelength study of a reddened starburst galaxy, found coincident with the potential radio and the X ray afterglow. We show that our strong I band upper limit makes of the GRB 001109 the darkest one localised by the BeppoSAX's NFI (Narrow Field Instrument), and it is one of the most constraining upper limits on GRB afterglows to date. Further to it, the implications of these observations in the context of dark GRBs are considered.

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arXiv2004

The Munich Near--Infrared Cluster Survey (MUNICS) -- VI. The stellar masses of K-band selected field galaxies to z ~ 1.2

We present a measurement of the evolution of the stellar mass function in four redshift bins at 0.4 < z < 1.2 using a sample of more than 5000 K-selected galaxies drawn from the MUNICS dataset. Our data cover the stellar mass range 10^10 < M/Msun < 10^12. We derive K-band mass-to-light ratios by fitting a grid of composite stellar population models of varying star formation history, age, and dust extinction to BVRIJK photometry. We discuss the evolution of the average mass-to-light ratio as a function of galaxy stellar mass in the K-band and in the B-band. We compare our stellar mass function at z > 0 to estimates obtained similarly at z=0. We find that the mass-to-light ratios in the K-band decline with redshift. This decline is similar for all stellar masses above $10^10 Msun. Lower mass galaxies have lower mass-to-light ratios at all redshifts. The stellar mass function evolves significantly to z = 1.2. The total normalization decreases by a factor of ~2, the characteristic mass (the knee) shifts towards lower masses and the bright end therefore steepens with redshift. The amount of number density evolution is a strong function of stellar mass, with more massive systems showing faster evolution than less massive systems. We discuss the total stellar mass density of the universe and compare our results to the values from the literature both at lower and higher redshift. We find that the stellar mass density at z~1 is roughly 50% of the local value. Our results imply that the mass assembly of galaxies continues well after $z \sim 1$. Our data favor a scenario in which the growth of the most massive galaxies is dominated by accretion and merging rather than star formation which plays a larger role in the growth of less massive systems.

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arXiv2004

The evolution of the luminosity functions in the FORS Deep Field from low to high redshift: I. The blue bands

We use the very deep and homogeneous I-band selected dataset of the FORS Deep Field (FDF) to trace the evolution of the luminosity function over the redshift range 0.5 < z < 5.0. We show that the FDF I-band selection down to I(AB)=26.8 misses of the order of 10 % of the galaxies that would be detected in a K-band selected survey with magnitude limit K(AB)=26.3 (like FIRES). Photometric redshifts for 5558 galaxies are estimated based on the photometry in 9 filters (U, B, Gunn g, R, I, SDSS z, J, K and a special filter centered at 834 nm). A comparison with 362 spectroscopic redshifts shows that the achieved accuracy of the photometric redshifts is (Delta z / (z_spec+1)) < 0.03 with only ~ 1 % outliers. This allows us to derive luminosity functions with a reliability similar to spectroscopic surveys. In addition, the luminosity functions can be traced to objects of lower luminosity which generally are not accessible to spectroscopy. We investigate the evolution of the luminosity functions evaluated in the restframe UV (1500 Angstroem and 2800 Angstroem), u', B, and g' bands. Comparison with results from the literature shows the reliability of the derived luminosity functions. Out to redshifts of z ~ 2.5 the data are consistent with a slope of the luminosity function approximately constant with redshift, at a value of -1.07 +- 0.04 in the UV (1500 Angstroem, 2800 Angstroem) as well as u', and -1.25 +- 0.03 in the blue (g', B). We do not see evidence for a very steep slope (alpha < -1.6) in the UV at z ~ 3.0 and z ~ 4.0 favoured by other authors. There may be a tendency for the faint-end slope to become shallower with increasing redshift but the effect is marginal. We find a brightening of M_star and a decrease of Phi_star with redshift for all analyzed wavelengths. [abridged]

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arXiv2003

The MUNICS Project: Galaxy Assembly at 0 < z < 1

We summarize the results obtained from the MUNICS K-band selected Galaxy survey thus far. MUNICS is a wide-area, medium-deep, photometric and spectroscopic survey selected in the K band, targeting randomly-selected high Galactic latitude fields. It covers an area of roughly one square degree in the K and J bands with optical imaging in the I, R, V, and B bands in 0.5 square degrees. The MUNICS photometric survey is complemented by spectroscopic follow-up observations down to limits of K<17.5 (wide area) and K<19.5 (smaller area). We have obtained 593 redshifts to this date. Here, we present results concerning the evolution of the K-band luminosity function to z ~ 1, both from the full photometric redshift sample and from the spectroscopic sample alone. We also report on new results concerning the evolution of the stellar mass function to z ~ 1. We fit stellar population synthesis models to our multicolor photometry to obtain M/L values for each source. We detect significant evolution in the stellar mass function and we find that more massive systems evolve faster in number density than less massive systems. We also measure the evolution of the total stellar mass density of the universe and find that about half the present day stellar mass formed since z ~ 1.

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arXiv2003

The TESIS project: revealing massive early-type galaxies at z>1

We present the preliminary results of an on-going near-IR low resolution spectroscopic follow-up of a complete sample of 30 bright (K'<18.5) EROs selected over 360 arcmin^2 from the MUNICH survey. Among the 13 EROs observed so far, 7 turned out to be early-type galaxies at 1.2 1.

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arXiv2003

The TESIS project: Are type 2 QSO hidden in X-ray emitting EROs?

Here we present the results obtained from the analysis of 75 ksec of XMM-Newton observations of a sample of EROs selected from one MUNICS field (K'<19.5 mag). We find 6 EROs with a X-ray counterpart down to a 2--10 keV flux limit of ~10^{-15} cgs. For all of them the X-ray--to--optical flux ratios and the 2--10 keV luminosities suggest the presence of AGN. In particular, a complete X-ray spectral analysis shows that high luminosity, obscured AGNs (i.e. QSO2 candidates) are present in 3 of them.

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arXiv2003

The TNG EROs Spectroscopic Identification Survey (TESIS)

We are carrying on a near-IR very low resolution spectroscopic follow-up in parallel with XMM-Newton observations of a complete sample of ~30 bright (K'<18.5) Extremely Red Objects (EROs) selected over an area of 360 arcmin^2 of the MUNICS survey. We here present the preliminary results of the spectroscopic and X-ray data analysis.

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