- ID:
- ivo://CDS.VizieR/J/ApJ/824/124
- Title:
- Galaxy stellar and baryonic mass functions
- Short Name:
- J/ApJ/824/124
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this work, we present galaxy stellar and baryonic (stars plus cold gas) mass functions (SMF and BMF) and their halo mass dependence for two volume-limited data sets. The first, RESOLVE-B, coincides with the Stripe 82 footprint and is extremely complete down to baryonic mass M_bary_~10^9.1^M_{sun}_, probing the gas-rich dwarf regime below M_bary_~10^10^M_{sun}_. The second, ECO, covers a ~40x larger volume (containing RESOLVE-A) and is complete to M_bary_~10^9.4^M_{sun}_. To construct the SMF and BMF we implement a new "cross-bin sampling" technique with Monte Carlo sampling from the full likelihood distributions of stellar or baryonic mass. Our SMFs exhibit the "plateau" feature starting below M_star_~10^10^M_{sun}_ that has been described in prior work. However, the BMF fills in this feature and rises as a straight power law below ~10^10^M_{sun}_, as gas-dominated galaxies become the majority of the population. Nonetheless, the low-mass slope of the BMF is not as steep as that of the theoretical dark matter halo MF. Moreover, we assign group halo masses by abundance matching, finding that the SMF and BMF, separated into four physically motivated halo mass regimes, reveal complex structure underlying the simple shape of the overall MFs. In particular, the satellite MFs are depressed below the central galaxy MF "humps" in groups with mass<10^13.5^M_{sun}_ yet rise steeply in clusters. Our results suggest that satellite destruction and stripping are active from the point of nascent group formation. We show that the key role of groups in shaping MFs enables reconstruction of a given survey's SMF or BMF based on its group halo mass distribution.
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Search Results
- ID:
- ivo://CDS.VizieR/VI/143
- Title:
- Galaxy stellar mass assembly
- Short Name:
- VI/143
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Semi-analytical models (SAMs) are currently the best way to understand the formation of galaxies within the cosmic dark-matter structures. They are able to give a statistical view of the variety of the evolutionary histories of galaxies in terms of star formation and stellar mass assembly. While they reproduce the local stellar mass functions, correlation functions and luminosity functions fairly well, they fail to match observations at high redshift (z>=3) in most cases, particularly in the low-mass range. The inconsistency between models and observations indicates that the history of gas accretion in galaxies, within their host dark-matter halo, and the transformation of gas into stars, are not followed well. We briefly present a new version of the GalICS semi-analytical model. With this new model, we explore the impact of classical mechanisms, such as supernova feedback or photoionization, on the evolution of the stellar mass assembly and the star formation rate. Even with strong efficiency, these two processes cannot explain the observed stellar mass function and star formation rate distribution or the stellar mass versus dark matter halo mass relation. We thus introduce an ad hoc modification of the standard paradigm, based on the presence of a no-star-forming gas component, and a concentration of the star-forming gas in galaxy discs. The main idea behind the existence of the no-star-forming gas reservoir is that only a fraction of the total gas mass in a galaxy is available to form stars. The reservoir generates a delay between the accretion of the gas and the star formation process. This new model is in much better agreement with the observations of the stellar mass function in the low-mass range than the previous models and agrees quite well with a large set of observations, including the redshift evolution of the specific star formation rate. However, it predicts a large amount of no-star-forming baryonic gas, potentially larger than observed, even if its nature has still to be examined in the context of the missing baryon problem.
- ID:
- ivo://CDS.VizieR/J/A+A/620/A39
- Title:
- Galaxy-wide IMF grids
- Short Name:
- J/A+A/620/A39
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The stellar initial mass function (IMF) is commonly assumed to be an invariant probability density distribution function of initial stellar masses. These initial stellar masses are generally represented by the canonical IMF, which is defined as the result of one star formation event in an embedded cluster. As a consequence, the galaxy-wide IMF (gwIMF) should also be invariant and of the same form as the canonical IMF; gwIMF is defined as the sum of the IMFs of all star-forming regions in which embedded clusters form and spawn the galactic field population of the galaxy. Recent observational and theoretical results challenge the hypothesis that the gwIMF is invariant. In order to study the possible reasons for this variation, it is useful to relate the observed IMF to the gwIMF. Starting with the IMF determined in resolved star clusters, we apply the IGIMF-theory to calculate a comprehensive grid of gwIMF models for metallicities, [Fe/H]{in}(-3, 1); and galaxy-wide star formation rates (SFRs), SFR{in}(10^-5^; 10^5^)M_{sun}_/yr. For a galaxy with metallicity [Fe/H]<0 and SFR>1 M_{sun}_/yr, which is a common condition in the early Universe, we find that the gwIMF is both bottom light (relatively fewer low-mass stars) and top heavy (more massive stars), when compared to the canonical IMF. For a SFR<1M_{sun}/yr the gwIMF becomes top light regardless of the metallicity. For metallicities [Fe/H]>0 the gwIMF can become bottom heavy regardless of the SFR. The IGIMF models predict that massive elliptical galaxies should have formed with a gwIMF that is top heavy within the first few hundred Myr of the life of the galaxy and that it evolves into a bottom heavy gwIMF in the metal-enriched galactic centre. Using the gwIMF grids, we study the SFR-H{alpha}relation and its dependency on metallicity and the SFR. We also study the correction factors to the Kennicutt SFRK-H{alpha} relation and provide new fitting functions. Late-type dwarf galaxies show significantly higher SFRs with respect to Kennicutt SFRs, while star-forming massive galaxies have significantly lower SFRs than hitherto thought. This has implications for gas-consumption timescales and for the main sequence of galaxies. We explicitly discuss Leo P and ultra-faint dwarf galaxies.
- ID:
- ivo://CDS.VizieR/J/MNRAS/455/2440
- Title:
- Gal. 2D phot. decompositions in r, g & i bands
- Short Name:
- J/MNRAS/455/2440
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We extend the catalogue of two-dimensional, Point-Spread-Function-corrected de Vacouleurs, Sersic, de Vacouleurs+Exponential, and Sersic+Exponential fits of ~7x10^5^ galaxies presented in Meert+ (2015, J/MNRAS/446/3943) to include the g and i bands. Fits are analysed using the physically motivated flagging system presented in the original text, making adjustments for the differing signal to noise when necessary. We compare the fits in each of the g, r, and i bands. Fixed aperture magnitudes and colours are also provided for all galaxies.
- ID:
- ivo://CDS.VizieR/J/ApJS/172/615
- Title:
- GALFIT result for GEMS galaxies
- Short Name:
- J/ApJS/172/615
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In the context of measuring the structures of intermediate-redshift galaxies with HST ACS surveys, we tune, test, and compare two widely used fitting codes (GALFIT and GIM2D) for fitting single-component Sersic models to both simulated and real galaxy data. Our study focuses on the GEMS survey (Rix et al., 2004ApJS..152..163R) with the sensitivity of typical HST survey data, and we include our final catalog of fit results for all 41495 objects detected in GEMS. Using simulations, we find that fitting accuracy depends sensitively on galaxy profile shape.
- ID:
- ivo://CDS.VizieR/J/A+A/617/A113
- Title:
- GalMer S0 remnants morphological properties
- Short Name:
- J/A+A/617/A113
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Major mergers are popularly considered too destructive to produce the relaxed regular structures and the morphological inner components (ICs) usually observed in lenticular (S0) galaxies. We have tested if major mergers can produce remnants with realistic S0 morphologies. We have selected a sample of relaxed discy remnants resulting from the dissipative merger simulations of the GalMer database and derived their morphological properties mimicking the typical conditions of current observational data. Only ~1-2Gyr after the full merger, we find that: 1) many remnants (67 major and 29 minor events) present relaxed structures and typical S0 or E/S0 morphologies, for a wide variety of orbits and even in gas-poor cases. 2) Most of them do not exhibit any morphological traces of their past merger origin under typical observing conditions and at distances as nearby as 30Mpc. 3) The merger relics are more persistent in minor mergers than in major ones for similar relaxing time periods. 4) No major-merger S0-like remnant develops a significant bar. 5) Nearly 58% of the major-merger S0 remnants host visually detectable ICs, such as embedded inner discs, rings, pseudo-rings, inner spirals, nuclear bars, and compact sources, very frequent in real S0s too. 6) All remnants contain a lens or oval, identically ubiquitous in local S0s. 7) These lenses and ovals do not come from bar dilution in major-merger cases, but are associated with stellar halos or embedded inner discs instead (thick or thin). We conclude that the relaxed morphologies, lenses, ovals, and other ICs of real S0s do not necessarily come from internal secular evolution, gas infall, or environmental mechanisms, as traditionally assumed, but they can result from major mergers as well.
227. GALPROP programme
- ID:
- ivo://CDS.VizieR/J/A+A/534/A54
- Title:
- GALPROP programme
- Short Name:
- J/A+A/534/A54
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We exploit synchrotron radiation to constrain the low-energy interstellar electron spectrum, using various radio surveys and connecting with electron data from Fermi-LAT and other experiments. The GALPROP programme for cosmic-ray propagation, gamma-ray and synchrotron radiation is used. Secondary electrons and positrons are included. Propagation models based on cosmic-ray and gamma-ray data are tested against synchrotron data from 22MHz to 94GHz.
- ID:
- ivo://CDS.VizieR/J/MNRAS/462/4336
- Title:
- GAMA. Stellar mass budget
- Short Name:
- J/MNRAS/462/4336
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We build on a recent photometric decomposition analysis of 7506 Galaxy and Mass Assembly (GAMA) survey galaxies to derive stellar mass function fits to individual spheroid and disc component populations down to a lower mass limit of log(M_*_/M_{sun}_)=8. We find that the spheroid/disc mass distributions for individual galaxy morphological types are well described by single Schechter function forms. We derive estimates of the total stellar mass densities in spheroids ({rho}_spheroid_=1.24+/-0.49x10^8^M_{sun}_Mpc^-3^h_0.7_) and discs ({rho}_disc_=1.20+/-0.45x10^8^M_{sun}_Mpc^-3^h_0.7_), which translates to approximately 50 per cent of the local stellar mass density in spheroids and 48 per cent in discs. The remaining stellar mass is found in the dwarf 'little blue spheroid' class, which is not obviously similar in structure to either classical spheroid or disc populations. We also examine the variation of component mass ratios across galaxy mass and group halo mass regimes, finding the transition from spheroid to disc mass dominance occurs near galaxy stellar mass ~10^11^M_{sun}_ and group halo mass ~10^12.5^M_{sun}_/h. We further quantify the variation in spheroid-to-total mass ratio with group halo mass for central and satellite populations as well as the radial variation of this ratio within groups.
- ID:
- ivo://CDS.VizieR/J/ApJ/787/90
- Title:
- Gamma-ray bursts minimum timescales
- Short Name:
- J/ApJ/787/90
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We develop a robust technique to determine the minimum variability timescale for gamma-ray burst (GRB) light curves, utilizing Haar wavelets. Our approach averages over the data for a given GRB, providing an aggregate measure of signal variation while also retaining sensitivity to narrow pulses within complicated time series. In contrast to previous studies using wavelets, which simply define the minimum timescale in reference to the measurement noise floor, our approach identifies the signature of temporally smooth features in the wavelet scaleogram and then additionally identifies a break in the scaleogram on longer timescales as a signature of a true, temporally unsmooth light curve feature or features. We apply our technique to the large sample of Swift GRB gamma-ray light curves and for the first time - due to the presence of a large number of GRBs with measured redshift - determine the distribution of minimum variability timescales in the source frame. We find a median minimum timescale for long-duration GRBs in the source frame of {Delta}t_min_=0.5 s, with the shortest timescale found being on the order of 10 ms. This short timescale suggests a compact central engine (3x10^3^ km). We discuss further implications for the GRB fireball model and present a tantalizing correlation between the minimum timescale and redshift, which may in part be due to cosmological time dilation.
- ID:
- ivo://CDS.VizieR/J/A+A/608/A133
- Title:
- Gas and dust in star-forming region rho OphA
- Short Name:
- J/A+A/608/A133
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate to what degree local physical and chemical conditions are related to the evolutionary status of various objects in star-forming media. rho Oph A displays the entire sequence of low-mass star formation in a small volume of space. Using spectrophotometric line maps of H_2_, H_2_O, NH_3_, N_2_H^+^, O_2_, OI, CO, and CS, we examine the distribution of the atomic and molecular gas in this dense molecular core. The physical parameters of these species are derived, as are their relative abundances in rho Oph A. Using radiative transfer models, we examine the infall status of the cold dense cores from their resolved line profiles of the ground state lines of H_2_O and NH_3_, where for the latter no contamination from the VLA 1623 outflow is observed and line overlap of the hyperfine components is explicitly taken into account. The stratified structure of this photon dominated region (PDR), seen edge-on, is clearly displayed. Polycyclic aromatic hydrocarbons (PAHs) and OI are seen throughout the region around the exciting star S1. At the interface to the molecular core 0.05pc away, atomic hydrogen is rapidly converted into H_2_, whereas OI protrudes further into the molecular core. This provides oxygen atoms for the gas-phase formation of O_2_ in the core SM1, where X(O_2_)~5x10^-8^. There, the ratio of the O_2_ to H_2_O abundance [X(H_2_O)~5x10^-9^] is significantly higher than unity. Away from the core, O_2_ experiences a dramatic decrease due to increasing H_2_O formation. Outside the molecular core, on the far side as seen from S1, the intense radiation from the 0.5pc distant early B-type star HD147889 destroys the molecules. Towards the dark core SM1, the observed abundance ratio X(O_2_)/X(H_2_O)>1, which suggests that this object is extremely young, which would explain why O_2_ is such an elusive molecule outside the solar system.
