Jan Snigula

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 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 1010 h-2 M☉. 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 toward 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 at both lower and higher redshifts. 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 ~ 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.

The Munich near-infrared cluster survey - I.:field selection, object extraction and photometry

The Munich Near-Infrared Cluster Survey (MUNICS) is a wide-area, medium-deep, photometric survey selected in the K′ band. It covers an area of roughly 1 deg2 in the K′ and J near-IR passbands. The survey area consists of 16 6×6 arcmin2 fields targeted at QSOs with redshifts 0.5<z<2 and seven 28×13 arcmin2 strips targeted at ‘random’ high Galactic latitude fields. 10 of the QSO fields were additionally imaged in R and I, and 0.6 deg2 of the randomly selected fields were also imaged in the V, R and I bands. The resulting object catalogues were strictly selected in K′, having a limiting magnitude (50 per cent completeness) of K′∼19.5 mag and J∼21 mag, sufficiently deep to detect passively evolving systems up to a redshift of z≲1.5 and luminosity of 0.5L*. The optical data reach a depth of roughly R∼23.5 mag. The main scientific aims of the project are the identification of galaxy clusters at redshifts around unity and the selection of a large sample of field early-type galaxies at 0<z<1.5 for evolutionary studies. In this paper – the first in a series – we describe the concept of the survey, the selection of the survey fields, the near-IR and optical imaging and data reduction, object extraction, and the construction of photometric catalogues. Finally, we show the J−K′ versus K′ colour–magnitude diagram and the R−J versus J−K′, V−I versus J−K′, and V−I versus V−R colour–colour diagrams for MUNICS objects, together with stellar population synthesis models for different star formation histories, and conclude that the data set presented is suitable for extracting a catalogue of massive field galaxies in the redshift range 0.5≲z≲1.5 for evolutionary studies and follow-up observations.

The FORS Deep Field: Field selection, photometric observations and photometric catalog ,

The FORS Deep Field project is a multi-colour, multi-object spectroscopic investigation of a ∼7 � × 7 � region near the south galactic pole based mostly on observations carried out with the FORS instruments attached to the VLT telescopes. It includes the QSO Q 0103-260 (z = 3.36). The goal of this study is to improve our understanding of the formation and evolution of galaxies in the young Universe. In this paper the field selection, the photometric observations, and the data reduction are described. The source detection and photometry of objects in the FORS Deep Field is discussed in detail. A combined B and I selected UBgRIJKsphotometric catalog of 8753 objects in the FDF is presented and its properties are briefly discussed. The formal 50% completeness limits for point sources, derived from the co-added images, are 25.64, 27.69, 26.86, 26.68, 26.37, 23.60 and 21.57 in U, B, g, R, I, J and Ks(Vega-system), respectively. A comparison of the number counts in the FORS Deep Field to those derived in other deep field surveys shows very good agreement.

The Munich Near-Infrared Cluster Survey. II. The K-Band Luminosity Function of Field Galaxies to z ~ 1.2

We present a measurement of the evolution of the rest-frame K-band luminosity function to z ~ 1.2 using a sample of more than 5000 K-selected galaxies drawn from the Munich Near-Infrared Cluster Survey (MUNICS) data set. Distances and absolute K-band magnitudes are derived using photometric redshifts from spectral energy distribution fits to BVRIJK photometry. These are calibrated using more than 500 spectroscopic redshifts. We obtain redshift estimates having an rms scatter of 0.055 and no mean bias. We use Monte Carlo simulations to investigate the influence of the errors in distance associated with photometric redshifts on our ability to reconstruct the shape of the luminosity function. Finally, we construct the rest-frame K-band LF in four redshift bins spanning 0.4 < z < 1.2 and compare our results to the local luminosity function. We discuss and apply two different estimators to derive likely values for the evolution of the number density, Φ*, and characteristic luminosity, M*, with redshift. While the first estimator relies on the value of the luminosity function binned in magnitude and redshift, the second estimator uses the individually measured {M, z} pairs alone. In both cases we obtain a mild decrease in number density by ~25% to z = 1, accompanied by brightening of the galaxy population by 0.5-0.7 mag. These results are fully consistent with an analogous analysis using only the spectroscopic MUNICS sample. The total K-band luminosity density is found to scale as d log ρL/dz = 0.24. We discuss possible sources of systematic errors and their influence on our parameter estimates. By comparing the luminosity density and the cumulative redshift distributions of galaxies in single survey fields to the sample averages, we show that cosmic variance is likely to significantly influence infrared selected samples on scales of ~100 arcmin2.

CLASH: z ∼ 6 young galaxy candidate quintuply lensed by the frontier field cluster RXC J2248.7−4431

We present a quintuply lensed z ∼ 6 candidate discovered in the field of the galaxy cluster RXC J2248.7−4431 (z ∼ 0.348) targeted within the Cluster Lensing and Supernova survey with Hubble (CLASH) and selected in the deep Hubble Space Telescope (HST) frontier fields survey. Thanks to the CLASH 16-band HST imaging, we identify the quintuply lensed z ∼ 6 candidate as an optical dropout in the inner region of the cluster, the brightest image having mag_(AB) = 24.8 ± 0.1 in the f105w filter. We perform a detailed photometric analysis to verify its high-z and lensed nature. We get as photometric redshift z_(ph) ∼ 5.9, and given the extended nature and NIR colours of the lensed images, we rule out low-z early-type and galactic star contaminants. We perform a strong lensing analysis of the cluster, using 13 families of multiple lensed images identified in the HST images. Our final best model predicts the high-z quintuply lensed system with a position accuracy of 0.8 arcsec. The magnifications of the five images are between 2.2 and 8.3, which leads to a delensed UV luminosity of L_(1600)∼0.5L^∗_(1600) at z = 6. We also estimate the UV slope from the observed NIR colours, finding a steep β = −2.89 ± 0.38. We use singular and composite stellar population SEDs to fit the photometry of the high-z candidate, and we conclude that it is a young (age <300 Myr) galaxy with mass of M ∼ 10^8 M_⊙, subsolar metallicity (Z < 0.2 Z_⊙) and low dust content (A_V ∼ 0.2–0.4).

Dark matter halo properties from galaxy–galaxy lensing

Die Forschungsergebnisse der letzten Jahre haben gezeigt, dass das Universum bei weitem nicht nur aus baryonischer Materie besteht. Tatsachlich scheinen 72% aus sogenannter Dunkler Energie zu bestehen, wahrend selbst vom verbleibenden Teil nur etwa ein Funftel baryonischer Materie zugeordnet werden kann. Der Rest besteht aus Dunkler Materie, deren Beschaffenheit bis heute nicht mit Sicherheit geklart ist. Ursprunglich in den Rotationskurven von Spiralgalaxien beobachtet, wurde die Notwendigkeit ihrer Existenz inzwischen auch in elliptischen Galaxien und Galaxienhaufen nachgewiesen. Tatsachlich scheint Dunkle Materie eine entscheidende Rolle in der Strukturbildung im Universum gespielt zu haben. In der Fruhzeit des Universums, als die Materieverteilung im Weltraum noch auserst gleichmasig war und nur sehr geringe Inhomogenitaten aufwies, bildeten sie die Kondensationskeime fur den gravitativen Kollaps der Materie. Numerische Simulationen haben gezeigt, dass der heute beobachtbare Entwicklungszustand des Universums erst durch die zusatzliche Masse Dunkler Materie ermoglicht wurde, die den strukturellen Kollaps erheblich beschleunigte und nur dadurch zur heute beobachtbaren Komplexitat der Strukturen fuhren konnte. Da Dunkle Materie nicht elektromagnetisch wechselwirkt, sondern sich nur durch ihre Schwerkraft bemerkbar macht, stellt der Gravitationslinseneffekt eine ausgezeichnete Methode dar, die Existenz und Menge an Dunkler Materie nachzuweisen. Der schwache Gravitationslinseneffekt macht sich zu Nutzen, dass die intrinsischen Orientierungen der Galaxien im Weltraum keine Vorzugsrichtung haben, gleichbedeutend mit ihrer statistischen Gleichverteilung. Die gravitationsbedingte koharente Verzerrung der Hintergrundobjekte fuhrt zu einer Abweichung von dieser Gleichverteilung, die von den Eigenschaften der Gravitationslinsen abhangt und daher zu deren Analyse genutzt werden kann. Diese Dissertation beschreibt die Galaxy-Galaxy-Lensing-Analyse von insgesamt 89 deg^2 optischer Daten, die im Rahmen des CFHTLS-WIDE-Surveys beobachtet wurden und aus denen im Rahmen dieser Arbeit photometrische Rotverschiebungs- und Elliptizitatskataloge erzeugt wurden. Das Galaxiensample besteht aus insgesamt 5×10^6 Linsen mit Rotverschiebungen von 0.05 < z_phot ≤ 1 und einem zugehorigen Hintergrund von insgesamt 1.7×10^6 Quellen mit erfolgreich gemessenen Elliptizitaten in einem Rotverschiebungsintervall von 0.05 < z_phot ≤ 2. Unter Annahme analytischer Galaxienhaloprofile wurden fur die Galaxien die Masse, das Masse-zu-Leuchtkraft-Verhaltnis und die entsprechenden Halomodellprofilparameter sowie ihre Skalenrelationen bezuglich der absoluten Leuchtkraft untersucht. Dies geschah sowohl fur das gesamte Linsensample als auch fur Linsensamples in Abhangigkeit des SED-Typs und der Umgebungsdichte. Die ermittelten Skalenrelationen wurden genutzt, um die durchschnittlichen Werte fur die Galaxienhaloparameter und eine mittlere Masse fur die Galaxien in Abhangigkeit ihres SED-Typs zu bestimmen. Es ergibt sich eine Gesamtmasse von M_total = 23.2+2.8−2.5×10^11 h^{−1} M_⊙ fur eine durchschnittliche Galaxie mit einer Referenzleuchtkraft von L∗ = 1.6×10^10 h^{−2} L_⊙. Die Gesamtmasse roter Galaxien bei gleicher Leuchtkraft uberschreitet diejenige des entsprechenden gemischten Samples um ca. 130%, wahrend die mittlere Masse einer blauen Galaxie ca. 65% unterhalb des Durchschnitts liegt. Die Gesamtmasse der Galaxien steigt stark mit der Umgebungsdichte an, betrachtet man die Geschwindigkeitsdispersion ist dies jedoch nicht der Fall. Dies bedeutet, dass die zentrale Galaxienmateriedichte kaum von der Umgebung sondern fast nur von der Leuchtkraft abhangt. Die Belastbarkeit der Ergebnisse wurde von zu diesem Zweck erzeugten Simulationen bestatigt. Es hat sich dabei gezeigt, dass der Effekt mehrfacher gravitativer Ablenkung an verschiedenen Galaxien angemessen berucksichtigt werden muss, um systematische Abweichungen zu vermeiden.

The Munich Near-Infrared Cluster Survey: Number Density Evolution of Massive Field Galaxies to z ~ 1.2 as Derived from the K-Band-selected Survey

We derive the number density evolution of massive field galaxies in the redshift range 0.4 < z < 1.2 using the K-band-selected field galaxy sample from the Munich Near-IR Cluster Survey. We rely on spectroscopically calibrated photometric redshifts to determine distances and absolute magnitudes in the rest-frame K band. To assign mass-to-light ratios, we use an approach that maximizes the stellar mass for any K-band luminosity at any redshift. We take the mass-to-light ratio, /LK, of a simple stellar population that is as old as the universe at the galaxys redshift as a likely upper limit. This is the most extreme case of pure luminosity evolution, and in a more realistic model /LK will probably decrease faster with redshift because of increased star formation. We compute the number density of galaxies more massive than 2 × 1010, 5 × 1010, and 1 × 1011 h-2 ☉, finding that the integrated stellar mass function is roughly constant for the lowest mass limit and that it decreases with redshift by a factor of ~3 and by a factor of ~6 for the two higher mass limits, respectively. This finding is in qualitative agreement with models of hierarchical galaxy formation, which predict that the number density of ~M* objects is fairly constant while it decreases faster for more massive systems over the redshift range that our data set probes.

Finding structures in photometric redshift galaxy surveys: an extended friends‐of‐friends algorithm

We present a modified version of the friends-of-friends (FOF) structure-finding algorithm, designed specifically to locate groups or clusters of galaxies in photometric redshift data sets. The main objective of this paper is to show that this extended friends-of-friends (hereafter EXT-FOF) algorithm yields results almost identical to the original FOF, if applied to a spectroscopic redshift data set, and a rather conservative catalogue of structures, in case of a data set with simulated photometric redshifts. Therefore, we create group catalogues for the first Center for Astrophysics Redshift Survey (CFA1), as well as for the Las Campanas Redshift Survey (LCRS), both of which being spectroscopic surveys, using FOF algorithms. We then apply our new algorithm to said surveys and compare the resulting structure catalogue. Furthermore, we bestow simulated photometric redshifts on the LCRS galaxies, and use the EXT-FOF to detect structures, which we compare in size and composition to the ones found in the original, spectroscopic data set. We will show that the properties of this modified algorithm are well understood and that it is suited for finding structures in photometric data sets. This is the first paper in a series of papers, dealing with the application of our new cluster finding algorithm to various photometric redshift galaxy surveys.

PROPERTIES OF M31. IV. CANDIDATE LUMINOUS BLUE VARIABLES FROM PANDROMEDA

We perform a study on the optical and infrared photometric properties of known luminous blue variables (LBVs) in M31 using a sample of LBV candidates from the Local Group Galaxy Survey by Masset et al. We find that M31 LBV candidates show photometric variability ranging from 0.375 to 1.576 mag in r P1 during a 3 yr time span observed by the Pan-STARRS 1 Andromeda survey (PAndromeda). Their near-infrared colors also follow the distribution of Galactic LBVs as shown by Oksala et al. We use these features as selection criteria to search for unknown LBV candidates in M31. We thus devise a method to search for candidate LBVs using both optical color from the Local Group Galaxy Survey and infrared color from the Two Micron All Sky Survey, as well as photometric variations observed by PAndromeda. We find four sources exhibiting common properties of known LBVs. These sources also exhibit UV emission as seen from Galaxy Evolution Explorer, which is one of the previously adopted methods of searching for LBV candidates. The locations of the LBVs are well aligned with M31 spiral arms as seen in UV light, suggesting that they are evolved stars at a young age given their high-mass nature. We compare these candidates with the latest Geneva evolutionary tracks, which show that our new M31 LBV candidates are massive, evolved stars with ages of 10-100 Myr.

THE M31 NEAR-INFRARED PERIOD-LUMINOSITY RELATION AND ITS NON-LINEARITY FOR δ Cep VARIABLES WITH 0.5 ≤ log (P) ≤ 1.7

We present the largest M31 near-infrared (F110W (close to J band), F160W (H band)) Cepheid sample so far. The sample consists of 371 Cepheids with photometry obtained from the Hubble Space Telescope PHAT program. The sample of 319 fundamental mode Cepheids, 16 first overtone Cepheids, and 36 type II Cepheids was identified using the median absolute deviation outlier rejection method we develop here. This method does not rely on priors and allows us to obtain this clean Cepheid sample without rejecting a large fraction of Cepheids. The obtained period-luminosity relations (PLRs) have a very small dispersion, i.e., 0.155 mag in F160W, despite using random phased observations. This remarkably small dispersion allows us to determine that the PLRs are significantly better described by a broken slope at 10 days than a linear slope. The use of our sample as an anchor to determine the Hubble constant gives a 3.2% larger Hubble constant compared to the Riess et al. sample.