Blue Sequence Research Articles

The dark nemesis of galaxy formation: why hot haloes trigger black hole growth and bring star formation to an end

Galaxies fall into two clearly distinct types: `blue-sequence' galaxies that are rapidly forming young stars, and `red-sequence' galaxies in which star formation has almost completely ceased. Most galaxies more massive than $3\times10^{10} M_\odot$ follow the red-sequence while less massive central galaxies lie on the blue sequence. We show that these sequences are created by a competition between star formation-driven outflows and gas accretion on to the supermassive black hole at the galaxy's center. We develop a simple analytic model for this interaction. In galaxies less massive than $3\times10^{10} M_\odot$, young stars and supernovae drive a high entropy outflow that is more buoyant that any diffuse corona. The outflow balances the rate of gas inflow, preventing high gas densities building up in the central regions. More massive galaxies, however, are surrounded by a hot corona. We argue that above a halo mass of $\sim 10^{12} M_\odot$, the supernova-driven outflow is no longer buoyant and star formation is unable to prevent the build up of gas in the central regions. This triggers a strongly non-linear response from the black hole. Its accretion rate rises rapidly, heating the galaxy's corona, disrupting the incoming supply of cool gas and starving the galaxy of the fuel for star formation. The host galaxy makes a transition to the red sequence, and further growth predominantly occurs through galaxy mergers. We show that the analytic model provides a good description of galaxy evolution in the EAGLE hydrodynamic simulations, and demonstrate that, so long as star formation-driven outflows are present, the transition mass scale is almost independent of subgrid parameter choice. The transition mass disappears entirely, however, if star formation driven outflows are absent.

Robust automatic photometry of local galaxies from SDSS

We present an automatic procedure to perform reliable photometry of galaxies on SDSS images. We selected a sample of 5853 galaxies in the Coma and Virgo superclusters. For each galaxy, we derive Petrosian g and i magnitudes, surface brightness profiles and color profiles. Unlike the SDSS pipeline, our procedure is not affected by the well known shredding problem and efficiently extracts Petrosian magnitudes for all galaxies. Hence we derived magnitudes even from the population of galaxies missed by the SDSS that represents 25% of all Local supercluster galaxies and ~95% of galaxies with g < 11 mag. After correcting the g and i magnitudes for Galactic and internal extinction, the blue and red sequences in the color magnitude diagram are well separated, with similar slopes. In addition, we study (i) the color-magnitude diagrams in different galaxy regions, the inner (r <= 1 kpc), intermediate (0.2R{Pet} <=r<= 0.3R{Pet}) and outer, disk-dominated (r>=0.35R{Pet})) zone, and (ii), we compute template color profiles, discussing the dependences of the templates on the galaxy masses and on their morphological type. The two analyses consistently lead to a picture where elliptical galaxies show no color gradients, irrespective of their masses. Spirals, instead, display a steeper gradient in their color profiles with increasing mass, consistently with the growing relevance of a bulge and/or a bar component above 10^{10} Modot.

Disc colours in field and cluster spiral galaxies at 0.5 ≲z≲ 0.8

We present a detailed study of the colours in late-type galaxy discs for ten of the EDisCS galaxy clusters with 0.5 < z < 0.8. Our cluster sample contains 172 spiral galaxies, and our control sample is composed of 96 field disc galaxies. We deconvolve their ground-based V and I images obtained with FORS2 at the VLT with initial spatial resolutions between 0.4 and 0.8 arcsec to achieve a final resolution of 0.1 arcsec with 0.05 arcsec pixels, which is close to the resolution of the ACS at the HST. After removing the central region of each galaxy to avoid pollution by the bulges, we measured the V-I colours of the discs. We find that 50% of cluster spiral galaxies have disc V-I colours redder by more than 1 sigma of the mean colours of their field counterparts. This is well above the 16% expected for a normal distribution centred on the field disc properties. The prominence of galaxies with red discs depends neither on the mass of their parent cluster nor on the distance of the galaxies to the cluster cores. Passive spiral galaxies constitute 20% of our sample. These systems are not abnormally dusty. They are are made of old stars and are located on the cluster red sequences. Another 24% of our sample is composed of galaxies that are still active and star forming, but less so than galaxies with similar morphologies in the field. These galaxies are naturally located in the blue sequence of their parent cluster colour-magnitude diagrams. The reddest of the discs in clusters must have stopped forming stars more than ~5 Gyr ago. Some of them are found among infalling galaxies, suggesting preprocessing. Our results confirm that galaxies are able to continue forming stars for some significant period of time after being accreted into clusters, and suggest that star formation can decline on seemingly long (1 to 5 Gyr) timescales.

UV-IR color profiles of the outer regions of 2K nearby S4G galaxies

AbstractWe present our new, spatially-resolved, photometry in FUV and NUV from images obtained by GALEX, and IRAC1 (3.6 μm) photometry obtained by the Spitzer Space Telescope. We analyzed the surface brightness profiles μFUV, μNUV, μ[3.6], as well as the radial evolution of the (FUV-NUV), (FUV - [3.6]), and (NUV - [3.6]) colors in the Spitzer Survey of Stellar Structures in Galaxies (S4G) galaxies (d &lt; 40 Mpc) sample. We defined the GALEX Blue Sequence (GBS) and GALEX Red Sequence (GBR) from the (FUV - NUV) versus (NUV - [3.6]) color-color diagram, populated by late-type star forming galaxies and quiescent early-type galaxies respectively. While most disk becomes radially bluer for GBS galaxies, and stay constant for GRS galaxies, a large fraction ( &gt; 50%) of intermediary GALEX Green Valley (GGV) galaxies’ outer disks are becoming redder. An outside-in quenching mechanism such as environmentally-related mechanisms such as starvation or ram-pressure-stripping could explain our results.

SUPERLUMINOUS SPIRAL GALAXIES

ABSTRACT We report the discovery of spiral galaxies that are as optically luminous as elliptical brightest cluster galaxies, with r-band monochromatic luminosity L r = 8–14L* (4.3–7.5 × 1044 erg s−1). These super spiral galaxies are also giant and massive, with diameter D = 57–134 kpc and stellar mass M stars = 0.3–3.4 × 1011 M ⊙. We find 53 super spirals out of a complete sample of 1616 SDSS galaxies with redshift z &lt; 0.3 and L r &gt; 8L*. The closest example is found at z = 0.089. We use existing photometry to estimate their stellar masses and star formation rates (SFRs). The SDSS and Wide-field Infrared Survey Explorer colors are consistent with normal star-forming spirals on the blue sequence. However, the extreme masses and rapid SFRs of 5–65 M ⊙ yr−1 place super spirals in a sparsely populated region of parameter space, above the star-forming main sequence of disk galaxies. Super spirals occupy a diverse range of environments, from isolation to cluster centers. We find four super spiral galaxy systems that are late-stage major mergers—a possible clue to their formation. We suggest that super spirals are a remnant population of unquenched, massive disk galaxies. They may eventually become massive lenticular galaxies after they are cut off from their gas supply and their disks fade.

SUPERMASSIVE BLACK HOLES AND THEIR HOST SPHEROIDS. II. THE RED AND BLUE SEQUENCE IN THE MBH–M*,SPH DIAGRAM

ABSTRACT In our first paper, we performed a detailed (i.e., bulge, disks, bars, spiral arms, rings, halo, nucleus, etc.) decomposition of 66 galaxies, with directly measured black hole masses, M BH, imaged at 3.6 &mgr; m ?> with Spitzer. Our sample is the largest to date and, for the first time, the decompositions were checked for consistency with the galaxy kinematics. We present correlations between M BH and the host spheroid (and galaxy) luminosity, L sph (and L gal), and also stellar mass, M &ast; , sph . ?> While most previous studies have used galaxy samples that were overwhelmingly dominated by high-mass, early-type galaxies, our sample includes 17 spiral galaxies, half of which have M BH &lt; 10 7 M &CircleDot; , ?> and allows us to better investigate the poorly studied low-mass end of the M BH &ndash; M &ast; , sph ?> correlation. The bulges of early-type galaxies follow M BH &prop; M &ast; , sph 1.04 &PlusMinus; 0.10 ?> and define a tight red sequence with intrinsic scatter &#x003F5; ( M BH &mid; M &ast; , sph ) = 0.43 &PlusMinus; 0.06 dex ?> and a median M BH / M &ast; , sph ?> ratio of 0.68 ± 0.04%, i.e., a &PlusMinus; 2 &sgr; ?> range of 0.1%–5%. At the low-mass end, the bulges of late-type galaxies define a much steeper blue sequence, with M BH &prop; M &ast; , sph 2 &minus; 3 ?> and M BH / M &ast; , sph ?> equal to 0.02 &percnt; ?> at M BH &approx; 10 6 M &CircleDot; . ?> We additionally report that (1) our Sérsic galaxy sample follows M BH &prop; M &ast; , sph 1.48 &PlusMinus; 0.20 , ?> a less steep sequence than previously reported; (2) bulges with Sérsic index n sph &lt; 2 , ?> argued by some to be pseudo-bulges, are not offset to lower M BH from the correlation defined by the current bulge sample with n sph &gt; 2 ; ?> and (3) L sph and L gal correlate equally well with M BH, in terms of intrinsic scatter, only for early-type galaxies—once reasonable numbers of spiral galaxies are included, the correlation with L sph is better than that with L gal.

THE HUBBLE SPACE TELESCOPE UV LEGACY SURVEY OF GALACTIC GLOBULAR CLUSTERS: THE INTERNAL KINEMATICS OF THE MULTIPLE STELLAR POPULATIONS IN NGC 2808

Numerous observational studies have revealed the ubiquitous presence of multiple stellar populations in globular clusters and cast many hard challenges for the study of the formation and dynamical history of these stellar systems. In this Letter we present the results of a study of the kinematic properties of multiple populations in NGC 2808 based on high-precision Hubble Space Telescope proper-motion measurements. In a recent study, Milone et al. have identified five distinct populations (A, B, C, D, and E) in NGC 2808. Populations D and E coincide with the helium-enhanced populations in the middle and the blue main sequences (mMS and bMS) previously discovered by Piotto et al.; populations A, B, and C correspond to the redder main sequence (rMS) that in the Piotto et al. was associated with the primordial stellar population. Our analysis shows that, in the outermost regions probed (between about 1.5 and 2 times the cluster half-light radius), the velocity distribution of populations D and E is radially anisotropic (the deviation from an isotropic distribution is significant at the ~3.5-sigma level). Stars of populations D and E have a smaller tangential velocity dispersion than those of populations A, B, and C, while no significant differences are found in the radial-velocity dispersion. We present the results of a numerical simulation showing that the observed differences between the kinematics of these stellar populations are consistent with the expected kinematic fingerprint of the diffusion towards the cluster outer regions of stellar populations initially more centrally concentrated.

HIGH-RESOLUTION IMAGING OF PHIBSSz∼ 2 MAIN-SEQUENCE GALAXIES IN COJ= 1 → 0

We present Karl G. Jansky Very Large Array observations of the CO J=1-0 transition in a sample of four $z\sim2$ main sequence galaxies. These galaxies are in the blue sequence of star-forming galaxies at their redshift, and are part of the IRAM Plateau de Bure HIgh-$z$ Blue Sequence Survey (PHIBSS) which imaged them in CO J=3-2. Two galaxies are imaged here at high signal-to-noise, allowing determinations of their disk sizes, line profiles, molecular surface densities, and excitation. Using these and published measurements, we show that the CO and optical disks have similar sizes in main-sequence galaxies, and in the galaxy where we can compare CO J=1-0 and J=3-2 sizes we find these are also very similar. Assuming a Galactic CO-to-H$_2$ conversion, we measure surface densities of $\Sigma_{mol}\sim1200$ M$_\odot$pc$^{-2}$ in projection and estimate $\Sigma_{mol}\sim500-900$ M$_\odot$pc$^{-2}$ deprojected. Finally, our data yields velocity-integrated Rayleigh-Jeans brightness temperature line ratios $r_{31}$ that are approximately unity. In addition to the similar disk sizes, the very similar line profiles in J=1-0 and J=3-2 indicate that both transitions sample the same kinematics, implying that their emission is coextensive. We conclude that in these two main sequence galaxies there is no evidence for significant excitation gradients or a large molecular reservoir that is diffuse or cold and not involved in active star-formation. We suggest that $r_{31}$ in very actively star-forming galaxies is likely an indicator of how well mixed the star formation activity and the molecular reservoir are.

STELLAR POPULATIONS AND THE STAR FORMATION HISTORIES OF LSB GALAXIES. V. WFC3 COLOR–MAGNITUDE DIAGRAMS

We present WFC3 observations of three low surface brightness (LSB) galaxies from the Schombert et. al LSB catalog that are within 11 Mpc of the Milky Way. Deep imaging at F336W, F555W and F814W allow the construction of the V-I color-magnitude diagrams (CMD) to M_I = -2. Overall 1869, 465 and 501 stellar sources are identified in the three LSB galaxies F415-3, F608-1 and F750-V1. The spatial distribution of young blue stars matches the H-alpha maps from ground-based imaging, indicating that star formation in LSB galaxies follows the same style as in other irregular galaxies. Several star complexes are identified, matching regions of higher surface brightness as seen from ground-based imaging. The color-magnitude diagrams for each LSB galaxy has the similar morphology to Local Volume (LV) dwarf galaxies, i.e. a blue main sequence, blue and red He burning branches and asymptotic giant branch (AGB) stars. The LSB CMD's distinguish themselves from nearby dwarf CMD's by having a higher proportional of blue main sequence stars and fewer AGB stars than expected from their mean metallicities. Current [Fe/H] values below -0.6 are deduced from the position of the red helium-burning branch (rHeB) stars in the V-I diagram. The distribution of stars on the blue helium-burning branch (bHeB) and rHeB from the U-V and V-I CMD indicate a history of constant star formation for the last 100 Myrs.

The structure and dynamics of the AC114 galaxy cluster revisited

We present a dynamical analysis of the galaxy cluster AC114 based on a catalogue of 524 velocities. Of these, 169 (32 per cent) are newly obtained at European Southern Observatory (Chile) with the Very Large Telescope and the VIsible MultiObject spectrograph. Data on individual galaxies are presented and the accuracy of the measured velocities is discussed. Dynamical properties of the cluster are derived. We obtain an improved mean redshift value z = 0.31665 ± 0.0008 and velocity dispersion σ = 1893^{+73}_{-82} km s^{-1}. A large velocity dispersion within the core radius and the shape of the infall pattern suggests that this part of the cluster is in a radial phase of relaxation with a very elongated radial filament spanning 12 000 km s-1. A radial foreground structure is detected within the central 0.5 h-1 Mpc radius, recognizable as a redshift group at the same central redshift value. We analyse the colour distribution for this archetype Butcher-Oemler galaxy cluster and identify the separate red and blue galaxy sequences. The latter subset contains 44 per cent of confirmed members of the cluster, reaching magnitudes as faint as Rf= 21.1 (1.0 mag fainter than previous studies). We derive a mass M200 = (4.3 ± 0.7) × 1015 M☉ h-1. In a subsequent paper, we will utilize the spectral data presented here to explore the mass-metallicity relation for this intermediate redshift cluster.

Color indices of core-collapse supernova host galaxies

Using data from different catalogues, we determined color indices of early type (E, L, and S0/a) core-collapse supernova host galaxies. These color indices were compared with the colors of the galaxies of the same morphological types but in which explosions of such supernovae have not been observed. It is shown that in the blue sequence of the color-magnitude diagram, the compared samples of galaxies differ with probability P = 95% in the relative frequencies of the (U − B)Tc0 and (U − B)T0 color indices in the intervals from \(- 0_ \cdot ^m 1\) to \(- 0_ \cdot ^m 01\) and \(0_ \cdot ^m 1\) to \(0_ \cdot ^m 19\). A difference in the relative frequencies with probability P = 99% was also obtained for the (B − V)Tc0 and (B − V)T0 colors in the interval \(0_ \cdot ^m 5 - 0_ \cdot ^m 59\). The calculated average colors of these intervals for the galaxies of both samples allow us to assume a significant proportion of the young population in them. The Kolmogorov-Smirnov test showed that the colors of the core-collapse supernova host galaxies and the early-type galaxies without explosions of such supernovae are similar on average with probability P = 95%, and the galaxies do not differ in stellar population content.

THE BINARY MASS TRANSFER ORIGIN OF THE RED BLUE STRAGGLER SEQUENCE IN M30

Two separated sequences of blue straggler stars (BSSs) have been revealed by Ferraro et al. (2009) in the color-magnitude diagram (CMD) of the Milky Way globular cluster M30. Their presence has been suggested to be related to the two BSS formation channels (namely, collisions and mass-transfer in close binaries) operating within the same stellar system. The blue sequence was indeed found to be well reproduced by collisional BSS models. In contrast, no specific models for mass transfer BSSs were available for an old stellar system like M30. Here we present binary evolution models, including case-B mass transfer and binary merging, specifically calculated for this cluster. We discuss in detail the evolutionary track of a $0.9+0.5 M_\odot$ binary, which spends approximately 4 Gyr in the BSS region of the CMD of a 13 Gyr old cluster. We also run Monte-Carlo simulations to study the distribution of mass transfer BSSs in the CMD and to compare it with the observational data. Our results show that: (1) the color and magnitude distribution of synthetic mass transfer BSSs defines a strip in the CMD that nicely matches the observed red BSS sequence, thus providing strong support to the mass transfer origin for these stars; (2) the CMD distribution of synthetic BSSs never attains the observed location of the blue BSS sequence, thus reinforcing the hypothesis that the latter formed through a different channel (likely collisions); (3) most ($\sim 60\%$) of the synthetic BSSs are produced by mass-transfer models, while the remaining $< 40\%$ requires the contribution from merger models.

THE GALEX /S 4 G UV–IR COLOR–COLOR DIAGRAM: CATCHING SPIRAL GALAXIES AWAY FROM THE BLUE SEQUENCE

We obtained GALEX FUV, NUV, and Spitzer/IRAC 3.6$\mu$m photometry for > 2000 galaxies, available for 90% of the S4G sample. We find a very tight "GALEX Blue Sequence (GBS)" in the (FUV-NUV) versus (NUV-[3.6]) color-color diagram which is populated by irregular and spiral galaxies, and is mainly driven by changes in the formation timescale ($\tau$) and a degeneracy between $\tau$ and dust reddening. The tightness of the GBS provides an unprecedented way of identifying star-forming galaxies and objects that are just evolving to (or from) what we call the "GALEX Green Valley (GGV)". At the red end of the GBS, at (NUV-[3.6]) > 5, we find a wider "GALEX Red Sequence (GRS)" mostly populated by E/S0 galaxies that has a perpendicular slope to that of the GBS and of the optical red sequence. We find no such dichotomy in terms of stellar mass (measured by $\rm{M}_{[3.6]}$), since both massive ($M_{\star} > 10^{11} M_{\odot}$) blue and red sequence galaxies are identified. The type that is proportionally more often found in the GGV are the S0-Sa's and most of these are located in high-density environments. We discuss evolutionary models of galaxies that show a rapid transition from the blue to the red sequence on timescale of $10^{8}$years.

GALAXY EVOLUTION IN THE MID-INFRARED GREEN VALLEY: A CASE OF THE A2199 SUPERCLUSTER

We study the mid-infrared (MIR) properties of the galaxies in the A2199 supercluster at z = 0.03 to understand the star formation activity of galaxy groups and clusters in the supercluster environment. Using the Wide-field Infrared Survey Explorer data, we find no dependence of mass-normalized integrated SFRs of galaxy groups/clusters on their virial masses. We classify the supercluster galaxies into three classes in the MIR color-luminosity diagram: MIR blue cloud (massive, quiescent and mostly early-type), MIR star-forming sequence (mostly late-type), and MIR green valley galaxies. These MIR green valley galaxies are distinguishable from the optical green valley galaxies, in the sense that they belong to the optical red sequence. We find that the fraction of each MIR class does not depend on virial mass of each group/cluster. We compare the cumulative distributions of surface galaxy number density and cluster/group-centric distance for the three MIR classes. MIR green valley galaxies show the distribution between MIR blue cloud and MIR SF sequence galaxies. However, if we fix galaxy morphology, early- and late-type MIR green valley galaxies show different distributions. Our results suggest a possible evolutionary scenario of these galaxies: 1) Late-type MIR SF sequence galaxies -> 2) Late-type MIR green valley galaxies -> 3) Early-type MIR green valley galaxies -> 4) Early-type MIR blue cloud galaxies. In this sequence, star formation of galaxies is quenched before the galaxies enter the MIR green valley, and then morphological transformation occurs in the MIR green valley.

THE TIP OF THE RED GIANT BRANCH DISTANCE TO THE PERFECT SPIRAL GALAXY M74 HOSTING THREE CORE-COLLAPSE SUPERNOVAE

M74 (NGC 628) is a famous face-on spiral galaxy, hosting three core-collapse supernovae (SNe):SN Ic 2002ap, SN II-P 2003gd, and SN II-P 2013ej. However its distance is not well known. We present a distance estimation for this galaxy based on the Tip of the Red Giant Branch (TRGB) method. We obtain photometry of the resolved stars in the arm-free region of M74 from F555W and F814W images in the Hubble Space Telescope archive. The color-magnitude diagram of the resolved stars shows a dominant red giant branch (RGB) as well as blue main sequence stars, red helium burning stars, and asymptotic giant branch stars. The I-band luminosity function of the RGB stars shows the TRGB to be at I_TRGB = 26.13 pm 0.03 mag, and T_RGB = 25.97 pm 0.03. From this we derive the distance modulus to M74 to be 30.04 pm 0.04 (random) pm 0.12 (systematic) (corresponding to a linear distance, 10.19 pm 0.14 pm 0.56 Mpc). With this distance estimate, we calibrate the standardized candle method for SNe II-P. From the absolute magnitudes of SN 2003gd, we derive a value of the Hubble constant, H_0 = 72 pm 6 (random) pm 7 (systematic) km s^-1 Mpc^-1. It is similar to recent estimates based on the luminosity calibration of Type Ia supernovae.

THE PAndAS FIELD OF STREAMS: STELLAR STRUCTURES IN THE MILKY WAY HALO TOWARD ANDROMEDA AND TRIANGULUM

We reveal the highly structured nature of the Milky Way stellar halo within the footprint of the PAndAS photometric survey from blue main sequence and main sequence turn-off stars. We map no fewer than five stellar structures within a heliocentric range of ~5 to 30 kpc. Some of these are known (the Monoceros Ring, the Pisces/Triangulum globular cluster stream), but we also uncover three well-defined stellar structures that could be, at least partly, responsible for the so-called Triangulum/Andromeda and Triangulum/Andromeda 2 features. In particular, we trace a new faint stellar stream located at a heliocentric distance of ~17 kpc. With a surface brightness of \Sigma_V ~ 32-32.5 mag/arcsec^2, it follows an orbit that is almost parallel to the Galactic plane north of M31 and has so far eluded surveys of the Milky Way halo as these tend to steer away from regions dominated by the Galactic disk. Investigating our follow-up spectroscopic observations of PAndAS, we serendipitously uncover a radial velocity signature from stars that have colors and magnitudes compatible with the stream. From the velocity of eight likely member stars, we show that this stellar structure is dynamically cold, with an unresolved velocity dispersion that is lower than 7.1 km/s at the 90-percent confidence level. Along with the width of the stream (300-650 pc), its dynamics points to a dwarf-galaxy-accretion origin. The numerous stellar structures we can map in the Milky Way stellar halo between 5 and 30 kpc and their varying morphology is a testament to the complex nature of the stellar halo at these intermediate distances.

The main sequences of NGC 2808: constraints on the early disc accretion scenario

[Abridged] A new scenario --early disc accretion-- has been proposed very recently to explain the origin of the multiple population phenomenon in Galactic globular clusters. It envisages the possibility that a fraction of low- and very low-mass cluster stars may accrete the ejecta of interacting massive binary (and possibly also fast rotating massive) stars during the fully convective, pre-main sequence stage, to reproduce the CN and ONa anticorrelations observed among stars in individual clusters. This scenario is assumed to be able to explain the presence (and properties) of the multiple populations in the majority of globular clusters in the Milky Way. Here we have considered the well studied cluster NGC 2808, which displays a triple main sequence with well defined and separate He abundances. Knowledge of these abundances allowed us to put strong constraints on the He mass fraction and amount of matter to be accreted by low-mass pre-main sequence stars. We find that the minimum He mass fraction in the accreted gas has to be $\sim0.44$ to produce the observed sequences and that at fixed initial mass of the accreting star, different efficiencies for the accretion are required to produce stars placed onto the multiple main sequences. This may be explained by differences in the orbital properties of the progenitors and/or different spatial distribution of intracluster gas with varying He abundances. Both O-Na and C-N anticorrelations appear naturally along the main sequences, once considering the predicted relationship between He and CNONa abundances in the ejecta of the polluters. As a consequence of the accretion, we predict no discontinuity between the abundance ranges covered by intermediate and blue main sequence stars, but we find a sizeable (several 0.1 dex) discontinuity of the N and Na abundances between objects on the intermediate and red main sequences.

Identification and cloning of putative water clarification genes of Moringa peregrina (Forssk.) Fiori in E. coli Xl 1 blue cells

Background:Water purification processes include the use of chemical compounds despite the concern that they may induce diseases. An ecological solution to this dilemma can come from the use of plant seeds for this purpose. Moringa peregrina (Forssk.) Fiori seeds have water clarification ability. Therefore, the aim of this work was to look for certain water clarification genes in M. peregrina.Materials and Methods:After preparation of M. peregrina callus, mRNA was extracted from these cells. After application of reverse transcriptase, the obtained cDNA (s) were used for PCR amplification of the desired genes using primers based on MO2.1 gene of Moringa oleifera. DNA amplification products were cloned in E. coli Xl1 blue cells and DNA sequences were compared with Mo1,2 gene in M. oleifera.Results:We obtained 3 PCR products (approximately 200, 300, and 400 bps).Conclusion:After comparison of the sequences of 300bp band obtained from M. peregrina with Mo1,2 gene in M. oleifera, it seems that 300bp band is a good candidate to investigate regarding its potential flocculent activity.

PHIBSS: MOLECULAR GAS, EXTINCTION, STAR FORMATION, AND KINEMATICS IN THEz= 1.5 STAR-FORMING GALAXY EGS13011166

We report matched resolution, imaging spectroscopy of the CO J=3-2 line (with the IRAM Plateau de Bure millimeter interferometer) and of the H-alpha line (with LUCI at the Large Binocular Telescope)in the massive z=1.53 main-sequence galaxy EGS 13011166, as part of the "Plateau de Bure high-z, blue sequence survey (PHIBSS). We combine these data with HST V-J-J-H-band maps to derive spatially resolved distributions of stellar surface density, star formation rate, molecular gas surface density, optical extinction and gas kinematics. The spatial distribution and kinematics of the ionized and molecular gas are remarkably similar and are well modeled by a turbulent, globally Toomre unstable rotating disk. The stellar surface density distribution is smoother than the clumpy rest-frame UV/optical light distribution, and peaks in an obscured, star forming massive bulge near the dynamical center. The molecular gas surface density and the effective optical screen extinction track each other and are well modeled by a 'mixed' extinction model. The inferred slope of the spatially resolved molecular gas to star formation rate relation depends strongly on the adopted extinction model and can vary from 0.8 to 1.7. For the preferred mixed dust-gas model we find a near linear slope.

FLAMES AND XSHOOTER SPECTROSCOPY ALONG THE TWO BLUE STRAGGLER STAR SEQUENCES OF M30

We present spectroscopic observations acquired with FLAMES and XSHOOTER at the Very Large Telescope for a sample of 15 Blue Straggler Stars (BSSs) in the globular cluster (GC) M30. The targets have been selected to sample the two BSS sequences discovered, with 7 BSSs along the blue sequence and 8 along the red one. No difference in the kinematical properties of the two groups of BSSs has been found. In particular, almost all the observed BSSs have projected rotational velocity lower than ~30 km/s, with only one (blue) fast rotating BSS (>90 km/s), identified as a W UMa binary. This rotational velocity distribution is similar to those obtained in 47 Tucanae and NGC 6397, while M4 remains the only GC studied so far harboring a large fraction of fast rotating BSSs. All stars hotter than ~7800 K (regardless of the parent BSS sequence) show iron abundances larger than those measured from normal cluster stars, with a clearcut trend with the effective temperature. This behaviour suggests that particle trasport mechanisms driven by radiative levitation occur in the photosphere of these stars, as already observed for the BSSs in NGC 6397. Finally, 4 BSSs belonging to the red sequence (not affected by radiative levitation) show a strong depletion of [O/Fe], with respect to the abundance measured in Red Giant Branch and Horizontal Branch stars. This O-depletion is compatible with the chemical signature expected in BSSs formed by mass transfer processes in binary systems, in agreement with the mechanism proposed for the formation of BSSs in the red sequence.