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تسجيل مستخدم جديدThe galaxy stellar mass function from CCSNe with improved photo-z techniques
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In Sedgwick et al. (2019) we introduced and utilised a method to combat surface brightness and mass biases in galaxy sample selection, using core-collapse supernovae (CCSNe) as pointers towards their host galaxies, in order to: (i) search for low-surface brightness galaxies (LSBGs); (ii) assess the contributions of galaxies at a given mass to the star-formation-rate density (SFRD); and (iii) infer from this, using estimates of specific star-formation (SF) rate, the form of the SF-galaxy stellar mass function (GSMF). A CCSN-selection of SF-galaxies allows a probe of the form of the SFRD and GSMF deep into the dwarf galaxy mass regime. In the present work, we give improved constraints on our estimates of the SFRD and star-forming GSMF, in light of improved photometric redshift estimates required for estimates of galaxy stellar mass. The results are consistent with a power-law increase to SF-galaxy number density down to our low stellar mass limit of $sim 10^{6.2}$ M$_{odot}$. No deviation from the high-mass version of the surface brightness - mass relation is found in the dwarf mass regime. These findings imply no truncation to galaxy formation processes at least down to $sim 10^{6.2}$ M$_{odot}$.
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We introduce a method for producing a galaxy sample unbiased by surface brightness and stellar mass, by selecting star-forming galaxies via the positions of core-collapse supernovae (CCSNe). Whilst matching $sim$2400 supernovae from the SDSS-II Super
nova Survey to their host galaxies using IAC Stripe 82 legacy coadded imaging, we find $sim$150 previously unidentified low surface brightness galaxies (LSBGs). Using a sub-sample of $sim$900 CCSNe, we infer CCSN-rate and star-formation rate densities as a function of galaxy stellar mass, and the star-forming galaxy stellar mass function. Resultant star-forming galaxy number densities are found to increase following a power-law down to our low mass limit of $sim10^{6.4}$ M$_{odot}$ by a single Schechter function with a faint-end slope of $alpha = -1.41$. Number densities are consistent with those found by the EAGLE simulations invoking a $Lambda$-CDM cosmology. Overcoming surface brightness and stellar mass biases is important for assessment of the sub-structure problem. In order to estimate galaxy stellar masses, a new code for the calculation of galaxy photometric redshifts, zMedIC, is also presented, and shown to be particularly useful for small samples of galaxies.
We measure the stellar mass function (SMF) of galaxies in the COSMOS field up to $zsim6$. We select them in the near-IR bands of the COSMOS2015 catalogue, which includes ultra-deep photometry from UltraVISTA-DR2, SPLASH, and Subaru/Hyper-SuprimeCam.
At $z>2.5$ we use new precise photometric redshifts with error $sigma_z=0.03(1+z)$ and an outlier fraction of $12%$, estimated by means of the unique spectroscopic sample of COSMOS. The increased exposure time in the DR2, along with our panchromatic detection strategy, allow us to improve the stellar mass completeness at high $z$ with respect to previous UltraVISTA catalogues. We also identify passive galaxies through a robust colour-colour selection, extending their SMF estimate up to $z=4$. Our work provides a comprehensive view of galaxy stellar mass assembly between $z=0.1$ and 6, for the first time using consistent estimates across the entire redshift range. We fit these measurements with a Schechter function, correcting for Eddington bias. We compare the SMF fit with the halo mass function predicted from $Lambda$CDM simulations. We find that at $z>3$ both functions decline with a similar slope in the high-mass end. This feature could be explained assuming that the mechanisms that quench star formation in massive haloes become less effective at high redshift; however further work needs to be done to confirm this scenario. Concerning the SMF low-mass end, it shows a progressive steepening as moving towards higher redshifts, with $alpha$ decreasing from $-1.47_{-0.02}^{+0.02}$ at $zsimeq0.1$ to $-2.11_{-0.13}^{+0.30}$ at $zsimeq5$. This slope depends on the characterisation of the observational uncertainties, which is crucial to properly remove the Eddington bias. We show that there is currently no consensus on the method to quantify such errors: different error models result in different best-fit Schechter parameters. [Abridged]
We present -- and make publicly available -- accurate and precise photometric redshifts in the ACS footprint from the COSMOS field for objects with $i_{mathrm{AB}}leq 23$. The redshifts are computed using a combination of narrow band photometry from
PAUS, a survey with 40 narrow bands spaced at $100r{A}$ intervals covering the range from $4500r{A}$ to $8500r{A}$, and 26 broad, intermediate, and narrow bands covering the UV, visible and near infrared spectrum from the COSMOS2015 catalogue. We introduce a new method that models the spectral energy distributions (SEDs) as a linear combination of continuum and emission line templates and computes its Bayes evidence, integrating over the linear combinations. The correlation between the UV luminosity and the OII line is measured using the 66 available bands with the zCOSMOS spectroscopic sample, and used as a prior which constrains the relative flux between continuum and emission line templates. The flux ratios between the OII line and $mathrm{H}_{alpha}$, $mathrm{H}_{beta}$ and $mathrm{OIII}$ are similarly measured and used to generate the emission line templates. Comparing to public spectroscopic surveys via the quantity $Delta_zequiv(z_{mathrm{photo}}-z_{mathrm{spec}})/(1+z_{mathrm{spec}})$, we find the photometric redshifts to be more precise than previous estimates, with $sigma_{68}(Delta_z) approx (0.003, 0.009)$ for galaxies at magnitude $i_{mathrm{AB}}sim18$ and $i_{mathrm{AB}}sim23$, respectively, which is $3times$ and $1.66times$ tighter than COSMOS2015. Additionally, we find the redshifts to be very accurate on average, yielding a median of the $Delta_z$ distribution compatible with $|mathrm{median}(Delta_z)|leq0.001$ at all redshifts and magnitudes considered. Both the added PAUS data and new methodology contribute significantly to the improved results.
We derive the low redshift galaxy stellar mass function (GSMF), inclusive of dust corrections, for the equatorial Galaxy And Mass Assembly (GAMA) dataset covering 180 deg$^2$. We construct the mass function using a density-corrected maximum volume me
thod, using masses corrected for the impact of optically thick and thin dust. We explore the galactic bivariate brightness plane ($M_star-mu$), demonstrating that surface brightness effects do not systematically bias our mass function measurement above 10$^{7.5}$ M$_{odot}$. The galaxy distribution in the $M-mu$-plane appears well bounded, indicating that no substantial population of massive but diffuse or highly compact galaxies are systematically missed due to the GAMA selection criteria. The GSMF is {fit with} a double Schechter function, with $mathcal M^star=10^{10.78pm0.01pm0.20}M_odot$, $phi^star_1=(2.93pm0.40)times10^{-3}h_{70}^3$Mpc$^{-3}$, $alpha_1=-0.62pm0.03pm0.15$, $phi^star_2=(0.63pm0.10)times10^{-3}h_{70}^3$Mpc$^{-3}$, and $alpha_2=-1.50pm0.01pm0.15$. We find the equivalent faint end slope as previously estimated using the GAMA-I sample, although we find a higher value of $mathcal M^star$. Using the full GAMA-II sample, we are able to fit the mass function to masses as low as $10^{7.5}$ $M_odot$, and assess limits to $10^{6.5}$ $M_odot$. Combining GAMA-II with data from G10-COSMOS we are able to comment qualitatively on the shape of the GSMF down to masses as low as $10^{6}$ $M_odot$. Beyond the well known upturn seen in the GSMF at $10^{9.5}$ the distribution appears to maintain a single power-law slope from $10^9$ to $10^{6.5}$. We calculate the stellar mass density parameter given our best-estimate GSMF, finding $Omega_star= 1.66^{+0.24}_{-0.23}pm0.97 h^{-1}_{70} times 10^{-3}$, inclusive of random and systematic uncertainties.
Context. The study of the galaxy stellar mass function (SMF) in relation to the galaxy environment and the stellar mass density profile, rho(r), is a powerful tool to constrain models of galaxy evolution. Aims. We determine the SMF of the z=0.44 clus
ter of galaxies MACS J1206.2-0847 separately for passive and star-forming (SF) galaxies, in different regions of the cluster, from the center out to approximately 2 virial radii. We also determine rho(r) to compare it to the number density and total mass density profiles. Methods. We use the dataset from the CLASH-VLT survey. Stellar masses are obtained by SED fitting on 5-band photometric data obtained at the Subaru telescope. We identify 1363 cluster members down to a stellar mass of 10^9.5 Msolar. Results. The whole cluster SMF is well fitted by a double Schechter function. The SMFs of cluster SF and passive galaxies are statistically different. The SMF of the SF cluster galaxies does not depend on the environment. The SMF of the passive population has a significantly smaller slope (in absolute value) in the innermost (<0.50 Mpc), highest density cluster region, than in more external, lower density regions. The number ratio of giant/subgiant galaxies is maximum in this innermost region and minimum in the adjacent region, but then gently increases again toward the cluster outskirts. This is also reflected in a decreasing radial trend of the average stellar mass per cluster galaxy. On the other hand, the stellar mass fraction, i.e., the ratio of stellar to total cluster mass, does not show any significant radial trend. Conclusions. Our results appear consistent with a scenario in which SF galaxies evolve into passive galaxies due to density-dependent environmental processes, and eventually get destroyed very near the cluster center to become part of a diffuse intracluster medium.
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